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!.FF!CTS OF .RESERVOIR RELEASES ON TAILWATER
ECOLOGY : A LITERATURE REVIEW
C. H. Walburg, et al
U.S. Fish 6 Wildlife Service
BowLing Green, Kentucky
September 1981
AD/A-105 058
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BUOU COIIPLETDJG FORM
I'· III& .. OIIIT NUM.RIII
E-81-12
12. GOVT ACCIIUION HOi ~:fC:1 .. 111NT'S C:ATA~OG NUIII.CIII
Teclmic·al Report . AD/Al05 058
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EFFECTS OF RESERVOIR RELEASES ON TAILWATER Final report
.JCOLOCY: A LITERAl'URE REVIEW
1. AUTMOIII(OIJ
I. ..CIU'OMIIINO OIIIG. IIIC .. OIIIT Nuti.Cit
Charles H. Walburg, Jerry F. Novotny, Kenneth E.
'Jacobs, William D. Swink, Terry M. Campbell, L .:;ONTIIIMOT 01111 GIIIIAMT NU111••••• , .
John Nestler, Gary E. Saul
1 ... CIIIP'01111111NO OIIIGANilATION NAIIII AfiD ADDIIIIIII
u. S.; F.isll & Wildlife Service 110. "IIIOGIIIAM CLb&MT, PIIIOJ&C:T, TAll< East Centra~ Reservoir Investigations AIIICA a WO"K UNIT NWiellllll
Bowling Green, Ky. 42101 EWQOS Task IIB u. s. Army Engineer Waterways Experiment Station
Environmental Laboratory ...
tz. ltllf'OitT OATil P. o. Box 631 September 1Q81 Vicksburg, Miss . 39180 IS. MU1118111t OP' "AGCS
It, CONTftOI.I.INCI OP'P'ICE NAMII AND AOOitCSS 216
Of'fice, Chief of Engineers, u. s . Army IS. ICCUIIItYY CI.AU. (el IN• ,_.,
Washington, D. c. 20314 Unclassified
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Biota Reservoirs •PIODutfD IT
Discharge (Water) Tail water NATIONAL TECHNICAL .
Impoundments Water qu ality IN FORM A liON SE.RVICE I
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·This document presents a review of tile often contradictory literature
de.cribing the effects of release waters on tBe tailwater environment and
biota. The physical and chemi.cal conditions found in tailwaters downstream
from varmwater and coldwater disd'J&rge impoundments are compared and con-
trasted t o those found in natural streams.
Reservoir disc barge. modify the pbysical, chemical, and biological
(Continued)
Unc l assified
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20. ABSTRACT (Continued) .
cbaracteristiss or the stream ecosystem. Physical and ch~cal characteristics
i.n tailvat.ers are prilllarily determ·ioed by the. depth; Yolume., and acbedul.e of
vater releases. The m.agnitude of change is related to the tn>e of reservoir
and to the design and operation of outlet s tructure~.
The structure. of the biotic ca.nmity ret'lec.ta the pbysieal and chemical
conditions existing io a pa:-ticular tailvater . 'l'be caamunity i.s composed or
organics, including nonnative species, that are adapted to this enTiroDIDent .
Tbe effects of the tailwater enviroDIDeot on the lire-history, physiology, and
abundance of selected speci es are described.
This information will aid in the development of reservoir discharge
guideLines tha't will enhance the quality of the tailvater environment to in-
crease project benefits.
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PREFACE
This report was prepared by the U. S. Department of the Interior,
U. S. Fish and Wildlife Service, National Reservoir Research Program
(NRRP), East Central Reservoir Investigations (ECRI), Bowling Gre.en, Ky .,
with the assistance of the Environmental Laboratory (EL), U. S. Army
Engineer Waterways Experimen.t Station ('WES), under Interagency Agreement
WES 79-04 d.a:ted 1 April 1980. This study forms part of the Environmental
and Wate·r Quality Operational Studies (EWQCS), Task IIB, Reservoir
Releases . The EWQOS Program is sponsored by the Office, Chief of
Enginee·rs, and is assigned to WES under the management of EL.
This report was written by Messrs. Charles H. Walburg, Jerry F .
llovotny, Kenneth E . Jacobs, William D. Svinlt, and Terry M. Campbell of
ECRI and Drs. John M. Nestler and Gary E. Saul, EL, WES. Mr. Charles H.
Walburg is the Chief of ECRI, and Mr. Robert M. Jenkins is the director
of the NRRP.
Preparation of this report vas under the direct supervision of .
Drs. llestler and Saul snd the general supervision of Mr. Joseph L.
Norton, Acting Chief, Water Quality Modeling Group, EL; Mr •. Donald L.
Robey, Chief, Ecosystem Resear ch and Simulation Division, EL; Dr. J'erane
L. Mahloch,. Program ·Manager, EWQOS, EL; and Dr. John Harrison, Chief,
EL.
· The Commander and Director of WES during this study was
COL Nelson P. Conover, CE . The Technical Director was Mr. Fred R. Brovn.
This report should be cited as follows:
Walburg, C. H. , Novotny, J. F ., Jacobs, K. E., Swink,
W. D., Campbell, T. M., Nestler, J., a .nd Saul, G. E .
1981. "Effects of Reserv:oir Rel.eases on Tailvater
Ecology: A .Literature Review," Technical Report
E-81-12, prepared by U. S. Department of~e Interior,
Fish and Wildlife Service, National Rese i Researc h
Program, East Central Reservoir Investigat ons, and
Environmental Laboratory, U. S. Army Engineer Waterways
Experiment Station, for the· U. S. Army Engineer Water-
ways Experiment Station, CE, Vicksburg, Miss.
1
PREFACE
PART I: INTRODUCTION •
Problem. . • • • •
Study Approach • •
CONTENTS
PART II: BASIC RESERVOIR LIMNOLOGY
Hydraulic Residence Time and Settling within Reservoirs ••
The,rmal Stratification
Dissolved Oxygen • . .
Nutrient Concentration •
Reduced Compounds ••••
PART III: RESERVOIR OUTLET STRUCTURES AND THEIR
IHPACT ON THE TAILWATER ENVIRONMENT ••
Design Considerations ••
Operation Considera~ions •
Summary. . • . • • • . . •
PART IV: Ph"YSICAL AND CHE.\fiCAL DESCRIPI'ION OF TAILWATERS •
Physical Characteristics
Temperature . . .. . . . . -. . . ..
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6
7
8
8
9
10
10
11
12
12
13
14
15
15
15 .
Flow ••• . . 18 . .
t ~~~ •
·Substrate •
Turbidity ••
Chemical Characteristics
Dissolved gases ••••••
•' . . . ' .
Hydrogen ion concentration and alkalinity •.
Particulate organic matter .•.
Nutrients • • . . • . • . • • •
Reduced compounds iD tailvaters
PART V: META.BOLISt-1 AND TROP'rliC STRUCTUR.E •
· · St'l'eams. • •
Te.ilvaters .
PART VI : AQUATIC INVERTEBRATES IN TAILWATERS •
Inver~ebrate Ecology
Streams • • • •
Tai1vaters. • •
Benthic Invertebrate Drift •
Streams • • • •
Tailvaters .••
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19
19
20
20
23
24
25
27
30
30
34
37
37
37
46
53
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Zooplankton. • . • • • • • • • • • • • • • • • . •
Tai.lwater Effect.s on Specific Invertebrate Taxa ••
Diptera . . • • . • • .
Tricboptera. •
Ephemeroptera
P1ecoptera. •
Mi s.cellaneous
PART VII: FISHES IN TAILWATERS •
Po1yodontida.e· (Paddlefishes) •
Pa.ddlefish. • • • • • • •
Paddlef'ish in tailwaters.
Clupeidae (Herrings) ••
Shad •••...••
Shad in tai1waters.
Sa.lmonidae (Trouts) .••
· Rain bo·w trout . . ...
Rainbo11 trout in tailwaters
Esocidae (Pike~) •
Pikes • • . .
Pikes in tai1waters •
Cyprinidae (Minnows) •.
Carp. • .•....
Carp in tailwaters.
Chubs . • • • • • •
Chubs in ta.ilvaters
True minnows ••
True minnows in tailwaters.
Shiners • • • • • • •
Shiners in tailwaters • • •
Stonerollers •.••••••
Stonerol1ers in tailwaters .
Da c es in tailwaters . • • .
Squawfishes and chiselmouths in
Cyprinids in Russian tailwaters
. Catostomidae (Suckers) • • .
Buffaloes • • • • • • .
Buffaloes in tailwaters
Suckers • • . • • ·• •
Suckers in tai1waters . •
Redhorse •••••••••
Redhorse in tailwaters .
3
tailwaters.
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55
57
58
59
60
60
61
63
63
64
65
67
67
68
69
70
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85
85
86
88 '
89
90
92
93
95
91
98
100
102
'103
103
104
104
106
106
108
109
113
116 ua
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Ictaluridae (Catfishes) ••.
Bullheads • • • • • • •
Bullheads i .n tailwater ·
Catfish .••••.••
Catfish in tailwaters
Madtoms •••••..
Madtoms in tailwaters • • • • • • • • •
Percichthyidae (Temperate Basses) ••••••
White bass. . . • . • • • . •
Temperate basses in tailwaters. • •••
Cent:rarchidae (Sunfishes). • . • • • • • •
Black basses ..•..•.••
Black basses in tailwaters. •
True sunfishes. • . • • . •
True sunfishes in tailwaters.
Crappie.s. • • • • • • .
Crappies in tailwaters.
Percidae (Perches) ••.••
Walleyes and saugers ..
Walleyes and saugers in tailwaters.
Darters • • . • • . •
Darters in tailwaters
Sciaenidae (Drums) ••.••
Freshwater drum
Freshwater drum in tailwaters •
Cottidae (Sculpins) .•••.
Sculpins. • . . • • • . •
Sculpins in tailwaters .•
PART VIII: CONCWSIONS . • . • .
Effects of Hypolimnetic Release on Downstream Biota.
E!fec~s of Epilimnetic Release on Downstream Biota .
Effects of Water Release Patterns on Downstream Biota.
Past Tailwater Research and Suggestions for Future
Study.
REFEP.EN CES .
APPENDIX A: ALPHABETICAL LIST OF THE 113 TAILWATERS
MENTIONED IN THE TEXT WITH LOCATION BY
APPENDIX B:
RIVER AND STATE, PROVINCE, OR COUNTRY.
LOCATION OF 105 RESERVOIR TAILWATERS
IN Tli:E UNITED STATES MENTIONED IN
THE TEXT • • • . • • • • • • • • • •
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119
121
122
124
125
126
126
127
128
130
130
133
135
138
141
143
145
145
147
150
151
152
152
153
154
154
155
157
157
160
162
165
168
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APPENDIX C: COMMON AND SCIENTI.FI·C NAMES OF FISHES
MENTIONED IN THE TEXT, .ARRANGED BY
F.AMILY • • • • • • • • • • • . • • • • ..
Part I: Fishes From North American Tailvaters •
Part II: Fishes from European Tailvaters. . .
APPENDIX D: LIFE HISTORY INFORMATION FOR THE MJST
COMMON FISH GROUPS MENTIONED IN THE TEXT
APPENDIX E: GLOSSARY
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EF?ECTS OF RESE.RVOIR RELEASES ON TAIL\lATER
ECOLOGY : A LITERATURE REVImJ
PART I : INTRODUCTION
Problem
1. The Corps of Engineers (CE) normally operates reservoir projects
to achieve downst.ream environmental quality objectives consistent with
proje.ct purposes. Presently, there a·re no quantitative approaches or re-
~iable guidelines for determining water releases necessary to ensure the
maintenance of a des.ired downstream aquatic environme.nt. Many en.viron-
mental quality requirements fo·r downstream habitat and biota are not well
understood or substantiated .
2. Reservoirs affect downstream aquatic habitats in a number of
ways, depending on project design and operation and specific environ-
mental requi:-em~nts of downstream biota. Large variations in flov
associated wi~h power-peaking operations may adversely affe~~ ~~~
stream fisheries during spawning periods, disrupt benthic communitie.s
that serve as food for fish, and 1 imi t stream recreation. Change·s in
temperature, dissolved gases, and other va.ter quality characteristics
associated with reservoir releases greatly influence the species
composition and abundance of the tailwater community .
3. The operation of reservoirs to achieve destred downstream
objectives is often complicated by conflicting requirements to improve
in-lake wa;:;er quality or demands of other proje.ct purpose.s. Periodi-
cally, minimum releases required to maintain downstream aquatic habitat
and associated stream recreation are greater than the releases required
to meet o·ther authorized project purpose.s . During these periods, pro-
blems associated with reservoir releases often become critical. Since
the benefit:; of maintaining or enhancing downstream aquatic habitat and
biota e.:-e difficult to quantify, justifying the allocatio·n of reservoir
storage for do\mstream releases is complicated. Nevertheless., minimum
releases are required to maintain adequate downstream habitat.
6
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Study Approach
4. The first task of the U. S. Fish and WiJdlife Ser<ice in pre-
paration of this report was to conduct an exhaustive literature search
o u the e.ffects of reservoir water releases on T.ailwater biota. An
..mnota::ted b i bliography vas prepared from the literature th&;t most dir-
ectly concerned tailwater problems (Walburg et al . 1980).
5. This report r e views available literature on the effects of
reservoir releases on tailwaters that support populations of varmwater
fish or trout. The extensive literature available on anadromous fish
is not included. This "state-of-the-art" report documents the relation
between changes in the quantity and quality of reservoir water releases
and the quality of the downstream aquatic envirorment. 'l'he review also
includes selected stream and river studies that have application to
tailwater problems. Tailwaters cited in this report are listed alpha-
.. betically in Appendix A together with name of river and l ocation (e.g.,
state of the United States or country). The geographic l ocations of
the 105 tailwaters located in the United States are shown in Appendix
B (Figure Bl).
6. To better understand the physical and chemical conditions
found in tailwaters, this report begins with a brief description o f
reservoir limnology, followed by a section on the design and operation
of reservoir outlet structures a nd how this can impac t the tailwater
environment. This is followed by a re'View of the physical, chemical,
and trophic conditions found in tail waters. A general review at in-
vertebrate ecology in both streams and tailwaters is then presented.
Life history requirements of fishes found in tailwaters are r eviewed,
together with a description of their response to the tailwater envi ron-
ment. Tailwater environments created by various management schemes for
reservoirs and tailwaters are discussed generally . Major physical and
chemical alterations are indicated, together with descript i ons of how
they affect organisms of the higher trophic levels. Finally, the
nature and scope of studies necessary to comp l ete the develoiDent of
conceptual models that can be used to predict the effect of changes
in reservoir management on t he ta.ilwater environment are indicated.
7
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PART II: BASIC RESERVOIR LDmOLOGY
7. Knowledge of reservoir limnology is fundamental to under-
standing water qual.ity characteristics i .n tailvaters. Wate.r quality
in. reservoi r changes with season. The exten.t of cbaDge reflec.ted in
the tailwater depends on the depth of wat.er withdrawal, project de-
sign, morph~etry of the tailwater channel, and local atmospheric
conditions. The following brief overview of reservoir limnology is
intended to provide suf'ficient background information for a biologist
or engineer to unders tand the relationship between reservoir biogeo-
~hemical processes and tailwater ecology; it is not inten~ed to be a
detailed d.iscussion of limnology. For a canprehensive description,
the reader should refer to the works of Hut.chin.so·n (1967), Wetzel
(1975'), and Cole (1975).
Hydraulic Residence Time and Settling within Reservoirs
:.
· 8.: In general, reservoirs with short hydraulic residence times ·
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have a reduc.ed impact on tailwaters because the water is discharged
before the effects of impoundment becc:me established. This type of
reservoir is often termed a flow-through or run-of-the-river pro·ject .
The discharge is usua.lly similar to the inflow· in oxyg.en concentra-
tion, temperature, turbidity, and nutrient concentration. Reservoirs
vi th long hydraulic residence times undergo· processes sc:mewhat similar
to those observed in lakes, although there are significant differences
(Neel 1963; Baxter 1977).
9. Reservoirs with long hydra.ulic residence times act as set-
tling basins in which suspended particles settle f'rc:m the water column.
They are effective in removing suspended material frc:m inflowing
streams or sediments washed into the reservoir during summer rains.
Turbid water is usually discharged into the tailwaters only after
long winter rains that are accc:mpanied by high runoff rates (Churchill
1967).
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Thermal Stratification
10. The .PTOCess or thermal stratification is a major factor in
altering the· wate.r quality of reservoirs. An understanding of thermal
stratification a.nd its influence on wat.er as it flows through a rese.r-
voir is essential to discu.ssion of water qualit·y in tailwaters.
11. Reservoirs strat,if'y thermally when solar radiation and in-
flows from warmer tributaries during th.e spring heat surfac.e vaters
more rapidly than the heat can be distributed throughout the water
column. This produces temperature and density differences be:tween the
surface water and the under~ying water, increasing t .he. resistance to
_mixing. Shearing between the surface and deepe.r waters inhibits add.i-
tlo.nal r;uxing and results in the formatio~ of an upper layer of warm
water ( epilimnion) and a deep layer of cold wate-r (hypolimnion) , vi th
a transitional layer be.tween the two (metalimnion). Following strati-
fication, mixing effects caused by wind. and air tempe.rature changes
are large·ly limited to the epilimnion.
12. Reservoir's destratify thermally when the loss of heat to t 'he
cooler atmosphere in l .ate summer and early fall exceeds the ,heat input --~ ,
from solar radiation. Complete thermal mixing begins when the surface
water cools and 'becomes. as dense. as the deeper water. Eventually tbe
entire water column loses its resistance to mixing and_ the reservoir
becomes thermally uniform (Wetzel 1975). Tributary inflows may
accelerate destratifica.tion by prQviding add-itional cool water.
13. 'l'he vater column in warm temperate reservoirs is essentially
of constant d-ensity during the· vinter, and little -thermal resistance
to mixing occurs. Convection curre.nts and relatively little vi.nd
action can thoroughly mix the entire water column (Churchill 1967). As
a result, the. c·bemical and physical characteristics of the water r•~in
un1form throughout the reservoir until spring. These reservoirs are
termed monomictic, sinc·e they circulate freely only during the vinter
months.
14. Reservoirs in cooler tempe.rate regions may beeome stratified
during the vinter. The coldest water (0-3°C) remains at the surface
9
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and the varmer, most dense vater (4•c) sinks to the bottom (Wetzel 1975).
These reservoirs are termed dimictic because they circulate freely tvice
during the year folloving spring and fall destratification.
15. Not all reservoirs thermally stratify during the summer.
Shallov reservoirs vith relatively rapid rates of flov-through and
exposure to extensive vinds usually remain vertically mixed. Temporary
temperature "differences" vhich form after extended periods of calm
veather and reduced discharge may be destroyed by vind action. These
reservoirs may, hovever, undergo periods of vinter stratification after
ice cover formation .
Dissolved OXYgen
16. Concentrations of dissolved oxygen in reservoirs are closely
associated ~lith the stratification process. In stratified reservoirs,
tbe epilimnion is vell aerated due to vind action, mixing resul.ting
from diurnal temperature fluctuation, and oxygen produced during photo-
s.ynthesis. Dissolved oxygen in the hypolimnion, bovever,·is limited to
that available at the time of stratification, and may be re·duced or
eliminated by the oxidation of organic matter that settles into the
hypolimnion from the epilimnion. These conditions persist until the
reservoir mixes vertically. Lov dissolved oxygen concentrations are
seldom a problem during the vinter, vhen lov 'vater temperatures sup-
press metabolic activity, and oxidation rates of organic compounds
are reduced. Hovever, lov dissolved oxygen can occur in ice-covered
lakes during the vinter vith resultant fish kills.
17. In unstratified reservoirs, comple.te circul.ation and frequent
aeration by vind action ensures that adequate oxygen is available
throughout the vater column. Lov oxygen concentrations may occur in
localized protected embayments and other areas not subject to frequent
circul.ation. Also, nighttime algal respiration may lover oxygen levels.
Nutrient Concentration
18. The import of nutrients from upstream or vatershed runoff is
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the main s.ource or reservoir enrichment. Me.xil:l.um inputs generally occur
after heavy rains. Excessive amounts of nutrients (e.g. , f .roo municipal
and agricultural sources) can cause· deterioration in overall water qual-
ity. Nutrients can also be released from the sediments under anoxic
conditions. These nutrients can be carried to the surface during lake
·curnover. In addition. wind-driven currents can incorporate sediments
and associated nutrients into the water column in shallov, unstratifie.d
reservoirs.
19. Phytoplankton growth is stimulated by an influx of nutrients.
In stratified reservoirs, phytoplankters continuously settle out of the
epili.mnion into the hypolimnion. Tbe loss of nutrients from the
epilimnion resulting from settling may limit further phytoplankton pro-
·duction, whereas, the hypolimnion becomes increasingly enriched as the
accumulation anc. decomposition of organic matter. proceeds. When the
reservoir destratifies, the nutrients that were restricted to the
hypolimnion are redistributed in the water column. The release of
nutrients to surface waters, where light is sufficient to stimulate . •,:
photosynthesis, results in increased phytoplankton production. In
unstratified reservoirs, there is continuous circulation of the. Wa.ter
column. Nutrients and organic matter are readily recyclable and remain
ava:.lable in the productive areas for continuous assimilation.
Reduced, Com-oounds
20. Anoxic conditions found in the hypolimnion of l&kes and reser-
voirs result in the formation o·f reduced species of iron, manganese,
.. sulfur, and nitrogen. These substances may become a nuisance to rec-
reational and industrial water users, and may be <;}etrimental to aquatic
li.f'e when they are released. These reduced compounds a.re c~nyerted to
less noxious, more assimil.:s.ble compounds in the oxidizing en-rtronment
of the epilimnion, and their effect. does not generally persist for more
than 24 hours. Objectionable iron, manganese, nitrogen, and sulfur
compounds are seldom a problem in well-mixed, unstratifie.d reservoirs.
11
PART III: RESERVOIR OUTLET STRUCTURES AND
THEIR IMPACT ON THE TAILWATER ENVIRONMENT
21. Water quality conditions in reservoir tailvaters are deter-.• ... ' . ~ .
mined by processes occurring in th~ reservoir (dis~ssed in the pre-
ceding section) and the design and operation of the project outlet
works. The following ·brief discussion is intended to provide general
information concerning the design and operation of r e servoir.outlet
structures. It should be emphasized that each project is unique in
·.design and-operation; therefore, many project features will not be
specifically discussed in this section.
Design Conside.rations
22. Most Corps of Engineers (CE) impoundments fulfill multiple
purposes including navigation, flood control, hydropower, recreation,
-·. Emphasis has been placed on effectively designing water supply, etc.
BDd operating projects to meet all inte.nded purposes. For approxi-•
•.•. o 0 ~' r •' .I • J 0 .. 1:~
mately the past 15 years, CE reservoir projects have been designed
considering tr ~ water quality of project releases.
23 . Numerous design options are available to assure t h at project
releases are compatible with tailwater habitat objectives. Most notable
is_ the ~ncorporation of a selective withdrawal structure which .can
j,,'
release water from various strata within the reservoir to meet down-
stream objectives. For selective withdrawal to be a viable alternative,
density stratification must occur within the reservoir. This strati -
fication may be due to vertical temperature differences within the
impoundment, and/or the occurrence of strati fication due to the con-
centration of dissolved constituents. Those reservoirs that are,
vertically well mixed have little need for selective withdrawal. Typi-
·cally, such reservoirs are shallow, may have a short hydraulic residence
time, and are often dominated by surface wind mixing .
24. Stratified reservoi rs provide an excellent opportunity for
effective operation of selective withdrawal structures. R.eleases can
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be made to meet downstream r equirements of tailvate~ ·fisher ies and also
reduce the impact of flood control oper ations on the tailvater .
25. Most older flood control proje~ts were designed primarily to
release vaters trca the bottom of t 'he r eservoir. Often, these water s
are lev in 'di.ssolved oxygen, but because of aerat.ion that occurs in the
outlet wor k.s it il .not. unc OJIIDon for dissolved oxygen in releas e waters
to approach 95 percent saturation. Releases from hydropower projects
receive little aeration due to the .r equirements to keep turbulence at
a minimum.
26. Release ot minimlD flows to meet downstream ha.bitat objec-
tives. is an important cons.ideration of project desi gn and operation.
Projects vith large bottom sluice gates are generally unable to dis-
charge low flows since the gates can not be operated with the neces-
sary prec-ision or they vibrate violently when attempting to pass low
nows und.er· high hydrostatic head . This problem can be over come with
flow bypass gates that can regulate releases to
Also, sluice gates can be designed to incorporate
the addition of lev
less than 1 m3/sec.
lov nov piggyback gates t o re.l ea.se mini.m\iin lev nows. . .,: . ·: •. ··:::~'~·l·~.!l .. ~·!!
' . ' I ,
Operation Considerations
27. Flood control operation of a project is designed to attenuate
and delay peaks in the inflow hydrograph, thereby r educ ing potential
damage caused by i ncreased downstr eam va-..er levels. The attenuation of
peak flood flows is obtained by storing water and releasing it throug'h
time. Ther efore, the reduction in peak flow resu;J.ts in l.:Jnger periods.
of high flov downstream. In many instances, reservoir disc harges are
reduced as high flovs enter upstream to permit the downstream tribu-
taries to discharge before r eservoir flood waters are released.
28. Flood releases from reservoirs are often hypoli mnetic because
the bo ttom sluice gates generally have the largest. capacity . Thus, if
epilimnetic withdrawals were occurring prior to the storm event, the
downstream area may experience cold hypolimnetic release waters during
the passage of the flood waters before returning to epilimnetic release
13
~:··:;, .. • .
.. . :
I. schedules. If the project has a selective withdrawal structure, a
portion of the releases can be made from near surface vaters to reduce.
changes in ·downstream temperatures.
29. Hydropower is generated by tvo types of projects. Run-of-the-
river projects generally provide baseload generation. The production
rate. of power is determined primarily by the amount of vater flowing
into the reservoir. Their relatively small capacity precludes their
use in hydropower peaking operations. The hydraulic residence time of
the water in run-of-the-river projects is usually quite short, and
therefore, the water quality of reservoir releases is often quite
similar to that of the reservoir inflow. Hydropower projects asso-
ciated with large reservoirs are ideal peaking power plants because of
their short response time. Thus, as demand peaks, the turbines can
generate electricity almost immediately. In general, hydropower pro-
ject releases reflect the demand for electricity, discharging only
minimum .lov flows during the weekend and at night. These projects are
. brought on line depend.ing on the demand for paver •
.......
Summary
30. Efforts to manage a reservoir· tailvater to reflect conditions
in an unregulated stream or river are impractical and often impossible
because of constraints imposed by the design and operation of.the pro-
ject. Thus, the quantity, quality, and t.iming of releases creates an
environment vhicb differs from a natural str@'am. Understanding the
.impacts of project releases on the tailvater environment, as vell as
efforts to minimize detrimental effects and possibly improve down-
stream conditions, are often determined by overall project design and
operation.
'
14
'
!
·.
..•.
PA.~ IV: PHYSICAL AND CHEMICAL DESCRIPTION OF TAIL WATERS
31. Impoundments cause three major physical modifications in
oatu=al stream conditions : (a) seasonal temperature changes are de-
layed a.nd the amplitude of diurnal and seasonal temperat;ure· fluctua-
tions may be reduced, (b) high natural streamf'lovs are reduced or
eliminated and replaced by more moderate discharges o.,er an extended
period of time; and (c) sediment transport is reduced (Neel 1963;
Maddock 1976). In addition, discharges may degrade the streambed and
banks, resulting in "armoring" of the streambed. Impoundments also
affect the ch~ical characteristics of the discharge including concen-
trations of dissolved oxygen, organic matter, nutrients, and reduced
compounds.
32. The magnitude of these physical and chemical I!I.Odi ficatiorus is
dependent on conditions vithin the reservoir (e.g., enrichment as
related to age, duration, and degree of thermal stratification; hydrau-
lic re.sidEmce time; density currents) and the de.pth and volume of dis-
charge (Neel 1963). The water quality of reservoir releases can be
further modified by conditions in the tailvater sueh as groundvater
inflov, runoff, streamside vegetation, and atmospheri.c influences.
Physical Characteristics
Temperature
33. Water temperatures in the tailvater are determined primarily
by ~limatic condjjJons and the ~th of release. Some tailvaters are
subject to sudden, drastic temperature changes, vhe:r-eas. in others the,
c·hanges are more subtle. Temperature alterations fre.quently result in
the elimination of organisms from habitats vhere. they might otherwise
survive. Many aquatic organisms present in a stream have distinct .
temperature requirements, and changes of l°C can affect their existence
(Britt 1962).-""' ... '"! ~l.e.s
34. Epilimnetic release dams on warmvater str~ams provide the
tailvater vith vell-oxygene.ted vater near or at atmospheric
15
I I
temperatures. Warmvater fish species found in these taiJvaters are
vell adapted to release water temperatures. Pfitzer (1954) noted
little difference in the varmvater fisheries in tailwaters below
Tennessee Valley Authority dams built on varmvater streams vhen water
releases vere from the epilimnion. Hovever, epilimnetic releases from.
reservoirs built on coldwater streams can increase summer vater temper-
atures in the tailwater and stress coldwater species . The temperatures
of epilimnetic discharges from Ennis Reservoir, Montana, vere 4°C higher
than those in the coldwater stream above the reservoir. This tempera-
ture increase caused grovth retardation in trout more than 270 mm long,
but did not affect smaller fish and invertebrates (Fraley 1978).
35. Water temperatures are levered belov hypolimnetic· release
reservoirs built on historically warmwater streams. Faunal changes are
generally :nore pronounced in rivers b e lov these reservoirs than in
rivers belov epilimnetic release or nonstratifying impoundments. Sev-
eral investigators have noted reductions in varmvater species caused
by coldwater discharges belov hypolimnetic release reservoirs built on
· ~water stre~s (Dendy and Stroud 1949; Edvard.s 1978) •
36. Coldwater discharges from d e ep-release dams on warmvater
streams may result in tailwater temperatures as much as 20°C lover than
the temperatures of Uriregulated streams of the region during the summer
(Ward and Stanford 1979). A l0°C reduction in wate.r temperature below
Norris Reservoir, Tennessee, changed the tailvater from a warmvater to
a coldwater streac (Tarzvell 1938). Average water temperatures 11.3 km
below Tenkiller Dam, Oklahoma, during June and July were reduced by
4. 3°C after impoundment (Finnell 1953) • Reductions in vat.er "bemperat,ure
have permitted the establishment of put-and-take trout fisheries in some
tailvaters that vere previously too warm to support trout.
37. During fall, hypolimnetic discharges from stratified reser-
voirs may provide varmer than normal vater to the tailvater, effec-
tively delaying the autumn decline in temper atures. River ice forma-
tions nay be delayed .during winter by lags in temperature change, and
some tailwe.ters may be kept completely ice-free by the release o·f 4°C
bottom vater (Neel 1963). Delays of 20-50 days in the spring rise in
16
I
4
•
-•JI'!·
·::.
' ·-.
water temperature have also resulted from release of hypolimnetic water
(Crisp 1977).
38. Seasonal temperature changes are also delayed in tailwaters
below nonst·ratified reservoirs. Normal temperature changes are re-
tarded because the time requir~d to cool or warm the reservoir is
significantly longer than the time required to cool o.r warm an .mregu-
la.ted stream. Additionally, diurnal and seasonal temperature fluctua-
tions take place in unregulated streams, whereas temperature.s in tail-
water areas are more nearly constant, especially near the reservo'ir
outflow. Marked reductions (up to• 80 percent) in diurnal temperature
fluctuation have been recorded (Fraley 1978). Before closure of
Flaming Gorge Dam, seasonal temperatures on the Green River, Utah,
ranged from 2°C in March to 22°C in July. After impoundment, water
temperature fluctuations were reduced and ranged between 2 and 10°C
(Vanicek and Krame.r 1969).
39. Severe vater temperature fluctuations may occur below dams . .
during periods of low flow or no flow, because of atmospheric influence.
Such periods are particularly characteristic of hYdropower projects
where changes in water discharge depend on pover demand. Temperature
fluctuations of 6-8°C may occur 2 to 3 times a day below these. dams
(Pfitzer 1968). If 2 or 3 consecutive days of no flow occurs, water
temperatures can approach mean air temperatures. The sudden release of ··
large volumes of cold bypolimnetic vater during the SUDIDer may cause
thermal shock. Fish kills have occurred when cold, bypolimnetic waters,
with reduced levels of dissolved oxygen, were suddenly released into a
tailvater after several days of little or no flow (Krenke! et. a.l. 1979)·~·
4o. Thermal changes caused by bypolimnetic discharge can persist
in a ta.ilvater for an extended distance downstream. The effects of an
altered temperature regime below a hypolimnetic release reservoir in
Canada were noted by the depletion of the benthic fauna 100 km down-
stream (Lelmlkuhl 1979). Air t~erature, discharge volume~ groundwater
and tributary additions, shade, and substrate type all play a role in
modifying the tailwater temperature as the water !!loves downstream. At
some point dovnstre~, where the influence of the reservoir lessens,
17
.·
. . . .. ~
tbe interaction of these factors results in tbe return a ·f the stream to
preimpoundrnent conditions .
. Flow
41. flatural streams are subject to large fluctuations in flov as
a result of variations in precipita.tion. Seasonally, flovs are highest
in the sp::-ing and lovest in the late summer .or early autumn, although
intermittent floods may occur as a result of periodic storms.
42. Impoundments can drastically alter the flow characteristics
in stream systems. Tailwater flows may be relatively unifonn or may
fluctuate frequently, depending on the method of dam operation and
downstream water requirements.
43. Flood control and irrigation dams general1y reduce.the mangi-
tude of flood flows, and release these flovs at reduced volumes over
longer pe:riods of time. The reduction or elimination of floods reduces
ban..'lt erosion and bed scour and decreases the amount o.f sediment washed.
into the tailwater from the flooded bottom lands. The, resultant. bank
and bed stability enhances the growth of aquatic and terrestrial vege-,....... .
tat ion (Neel 1963). The encroachment of streamside vegetation, .. vt;i_ch
is important in temperatw:-e regulation, shading, and in providing food.
for invertebrates, can further increase bank and. floodplain st.abUity.
However, such increased vegetative encroachment may resul·t ir+ the
eventual loss of part of the wate.r-carrying capacity of the stream
channel through a re.duction in channel size (Bovee 1975; Maddo.ck 1976).
44. Uniform flovs below ·nood control and irrigation dam.s often
benefit'the invertebrate community through the establishment of dense
mat.s of periphytic algae. These algal mats constitute both a habitat
and a food supply for benthic organisms incapable of living in a more
barren stream. Hovever, these mats may elim.inate species adapted to
clean rock surfaces (Ward 1976c).
45. Flov fluctuations are more frequent an.d of greater magnit.ude
below hydropove·r dams than in natural streams. Large daily flow fluc-
tuations often preclude the establishment of permanent strei!JIIS'ide
vegetation. The alternate inundation and exposure of the streambed.,
coupled with extreme variations in flov, may remove much of the aquatic
18
•
•
,,
•
biota from the tai1wate~ (Neel 1963). A sudden increase in !"low :t.a.y
remove algae, macrophytes, and sedimentary detritus, in addition to
benthic invertebra~es. Sudden decreases in flow may strand attached or
immobile species and result in their desiccation (Lowe 1979). Overall,
the diversity and abundance ·of tailwater habitat and fish and inverte-
brate food supply may be• s i gnificantly reduced by radically fluctuating
flows (Neel 1963). Rec.ent studies (Matter et al. 1981) demonstrs.te
that the surge of water from a peaking hydropower plant, and resultant
bed scour may indirectly bene.fit tailwater fish by making benthic foods
more available.
Substrate
46. Because reservoirs act as sediment traps, there is usually
little sediment in reservoir discharge. 'This loss of sediment in the
discharge, coupled with the removal of fine particles by the current
below the dam, results in a tailwater streambed composed primarily of
coarse cobble and bedrock. Ultimately an equilibrium is reached be-
"'··
tween the particle size of the remaining substrate and the stream's
capacity to transport material. Upon reaching this equilibrium,
further degradation of the tailwater streambed by scouring is halted
(Komura and Simmons 1967). Increased flow rates below some hydropower
facilities reduce bank and streambed stability, thereby causing in-
creased bank erosion, streambed scour, and eventually armoring·.
Scaller sediment particles are swept downstream and deposited in pools
and slackwater areas .
Turbidit Y
47. Turbidity can reduce or eliminate aquatic life in a stream .
Decreased light penetration in turbid s~reams inhibits the establish-
ment and maintenance of autotrophic plants, wi.ich may in turn effec-
tively limit higher life forms (Ruttner 1963). Additionally, sedi-
mentation resulting from turbid conditions eliminates invertebrate
habitats by filling the interstices of gravel substrates. Sedimenta-
tion may also cover fish spawning sites and interfere with oxygen
transport to buried fish eggs (Fry 1960).
19
48. Tailwaters are usually clearer (less turbid) than the reser-
voir inf1ow, particularly below deep-release reservoirs. Turb~dity
below reservoirs is significantly affected by sedimentation within the
reservoir-, density currents, discharge depth from the dam, and the in-oft->
flow from surface runoff and tributary additions. Turbidity was re-~~ \J' 0 .. duced up to sixtyfold in the tailwater below Yellowtail Dam, Montana, /.
by the settling of suspended matter within the reservoir (Soltero et al.
1973). Density currents carrying fine suspended matter, however, may
sometimes flov beneath or through the main 'body of wat-er in strati.fied
reservo1rs and !be discharged directly into the tailvaters with little
alteration within the reservoir (Churchill 1958). In these instances,
mineral concentrations and turbidity may increase significantly in the
tailvater. Turbid conditions may also result from the flushing of
loose materials into tailvaters from unstable riverbeds and streambanks
during periods of high discharge, and from tributary inflov.
Chemical Characteristics
' ·.
Chemical properties that may affect the tailwater biota are·
. .
the concentration of dissolved gases (i.e., oxygen, nitrogen), pH,
particulate organic matter, available nutrients, and reduced compounds.
Because of the variability of factors involved in altering water
quality, rev general statements can be made that are applicable to all
tailwaters. Chemical properties of the water immediately below a dam
depend on vater quality within the reservoir at the level of release~
As the ve.ter moves downstream, local conditions influ~nce wat.er quality
and tend to characterize each individual tailvater (Pfitzer 1954).
Di .ssol ved gases
50. Dissolved oxygen. The concentration of dissolved oxygen in
an aquatic system is dependent on water temperature, biological oxygen
demand, atmosphe·ric exchange, and primary production. Water t~e.ra
ture determines the solubility of oxygen, and thus the &mQUilt of avail-
able oxygen in streams. This is an important factor in regulat.ing the
metabolic rates of cold-blooded animals, since their rates of
20
I
•
. '·
•.
II!'.
metabolism increase vith temperature. The solubility of oxygen .de-
creases as vater temperature increases. At 100 percent satur.ation,
14.16 mg/1 of dissolved oxygen may be in solution at 0°C but only
7.53 mg/1 at 30°C (Boyd 1979). Decanposition rates of organic matter
increase with increasing temperature, resulting in an additional deple-
tion of oxygen content. The rate of decompcsition generally increases
between 5 and 38°C. Temperature increases of 10°C o·f'ten double the
rates of decomposition and oxygen consumption (Boyd 1979).
51. Mo.st st.reams are relatively vell oxygenated due to turbulent
f'lovs and continual atmospheric exchange. In quiet pool areas with
dense algal vegetation, diurnal va.ri·ations in the concentration of
dissolved oxygen are directly linked to the amount of phot.osynthesis
and respiration taking place in the system (Hoskin 195~). Oxygen con-
centrations are highest during the day and lovest at night.
52. The concentration of O~Jgen in tailwaters depends on the
·type of reservoir, depth of v--ater releas~, vater mixing during re·lease
fran t ·he. dam, and downstream flov conditions. Low dissolved oxygen
concentrations normally do not occur belov surface-release reservoirs: -
Water from the epilimnioh is usually well oxygenated as a result of
photosynthesis :;.nd a.tmospheric gas exchange.
53. In deep-release reservoirs, biological decomposition of
organic matter in the hypolimnion during the summer may result in the
discharge of poorly oxygenated water into the tailwater. The low
oxygen content of these waters may not satisfy the biological and
chemical demand, especiall.y if there are additions of domestic and
. industrial pollution downstream from the dam (Fish 1959).
54. Tailwater oxygen levels may also be reduced by the oxidation
of iron and manganese present in hypolimnetic releases. This reduction
may cause physiological stress to the aquatic community and further
reduce the assimilation of organic wastes by stream organisms. Low-
oxygen conditions may also intensify ~he potentially toxic effects of
other chemical constituents-including ammonia and hydrogen sulfide,
which are ott.en present in the anoxic hypolimnetic water.
21
·'
·55.· Reaeration of deoxygenated water can be rapid, and serious
oxygen depletions can be avoided if tailwater conditions are such that
biologic·al ·and chemical oxygen demands are not excessive. Wirth et al.
(1970) documented a consistent concentration of 7 ms/1 dissolved oxygen
in discharges from a deep-release reservoir in which the hypolimnion
was devoid of oxygen. Reaeration during discharge is credited with
maintaining the high dissolved oxygen level.
56. The rate of reaeration below deep-release reservoirs depends
on the turbulence of the flow in the tailwater, atmospheric influence,
and extent of photosynthesis by aquatic vegetation below the dam. Low
oxygen levels may persist farther downst.ream during peak flow periods,
when riffle areas are inundated and more laminar now conditions exist.
Be~ov an Oklahoma hydropower project, dissolved oxygen concentrations
were low ( 1. 5 mg/1) for 3. 2 km downstream during peri.ods of moderate
discharge, but extended 8 km downstream (2.0 mg/1) at peak flows
(Summers 1954).
57. Oxygen concentrations greater than 5 mg/1 are generally pre-
ferred ·by most stream fish (~·y 1 ~60). They appea~ to survive well in
streams where dissolved oxygen content occasionally f~ls "below 5 mg/1
at night but !' ises abov·e this level during the day. Certain current-
oriented aq·..tatic invertebrates can Yi thstand dissolved oxygen conc.en-
trations less than 1 mg/1 if current velocities remain high (Bovee
1975).
58. When dissolved oxygen deficiencies occur in tailwaters, they
adversely affect the health of fish through suffocation, growth retar-
dation1 and decreased disease resistance. Macroinvertebrates may also
be adversely affected,. but tolerant organisms usually replace those
that have abandoned the a.reas because of lov oxygen levels. Oxygen
reductions that are no·t great enough to retard fish grovth generally
do not impair fish food resources (Doudoroff and Shumvay 1967).
59. Gas su·,ersaturat ion. Gas supersaturation can. occu.r in tail-
waters when water is spilled over high dams, trapping air and plunging
it to the stream below where hydrostatic pressure is sufficient to
increase solubility of atmospheric gases (Weitkamp and Katz 1980). ~he
22
,
•
·'
:
. ·~. . . ....... .
···.~ .•
..
'·'.
high levels of dissolved gases produce em.bolism.s in a variety of
fishes and invertebrates. The ~ttpersaturated gases come out of
solution within the fish's or invertebrate's body and for.n bubbles
under the skin; severe cases can cause death. The condition is most
caumon in tailwaters below hydropower reservoirs in the Pacific !lorth-
west and has been attributed to both spill~ay and turbine releases
( Beiningen !!..."ld Ebel 1970; Ruggles and Watt 1975}. Crunkilton et a.l.
(1980} reported on the' occurrence. of gas supersaturation in a '.tar::l-
wa.ter tailwa.ter in Missouri. Spillway deflectors are reported to
effectively reduce the level of gas supersaturatic!! in water pass:.ng
over a spillway (Weitk.amp and Katz 1980}.
Hydrogen ion concentration and alka.lini ty
·. ·.
60. The distribution of organisms in an aquatic system is dete!'-
mined to a large extent by the hydrogen ion concentration (pH} of the
water. Changes in the pH of surface waters a.re often brought about by
addition or removal of co 2 during photosynthetic activity, decomposi-
tion of organic matter • • and gas exchange. Fluctuations in pH, UDless . , ·,
extreme, are not harmful in themselves, but variations may intensify
or dec·rease the effect of toxic substances within the vater column
(~ey 1960}. Waters with a pH from 6.5 to 8.6 are most productive,
and fish populations are unaffected by slight deviations within this
range (Fry 1960}. Additions of acid mine drainage or industrial
wastes may result in extreme deviations fr-om these acceptable limits
and stress some aquatic organisms (Edwards 1978}. Aquatic insects
have been shown to have little tolerance for pH below 4 (Canton and
Ward 1977}. Effects on !ish become lethal when the pH falls below 4
or.rises above 11 (Swingle 1961}.
61. Diurnal fluctuations in pH of unpolluted surface va~ers
are· reduced through buffering by an alkalinity system of carbonates
and bicarbO[tates, and tho! degree of buffering effectiveness depends
on the concentration of these substances in the watershed. :otal
alkalinity may range from less than 5 mg'/1 as Caco 3 (little buffer-
ing capacity present} to several hundred milligrams per litre (Boyd
1979}.
23
Productivity in natural waters is related to their total alkalinity
(Turner 1960; Bayes and Anthony 1964). 'Waters vitbin an alkalinity
range of 20 to 400 mg/1 are generally considered biologically more
productive than those vith higher or lower alkalinities (Moyle 1945).
62. There are no apparent trends in pH and alkalinity value~ in
tailvaters, other than seasonal changes brought about b· thermal stra-
tification (Vanicek 1967; Pearson and Franklin 1'968). Bacterial de-
composition of organic matter in the hypolimnion increases the concen-
tration of carbon dioxide, thereby reducing the pH in the tailvater.
Turbulence in tailvaters increases gas exchange, which reduces the con-
·centration of carbon dioxide; consequently pH rises as the water flows
downstream. Alkalinity values in tail~ters below bypolimnetic release
reservoirs are reduced during spr'ing runoff but increase during the
summer, when the reservoirs become thermally stratified (Vanicek 1967;
Charles and McLemor• 1973; Ha~nan and Young 1974).
Particulate organic matter
63. Particulate organic matter (POM), the ·organic component of
the seston (Cole 1975); is the main food supply for de·tri ti vo;es in
natural stream ecosystems. Concentrations of POM present in e st·ream
are often positively correlated vith flow rates, which are, in turn,
determi ned by the amount of rainfall in the watershed (Webster et al.
1979).. Concentrati,-,ns of POM are highest during lea.f fall in autumn
and this source is gr<Wually depleted from the si.:-eam during the rest
of the year.
64. The POM t'!!IS h! separated into coarse and fine fractions. The
coarser materials tend ·.;o .move only a short distance downstream before
they are trapped by obstructions and reduced in si.ze by mechanical Uld
biologic.al processes. The finer particles are generally carried
farther dovnstream until a reduction in the flow velocity allows the
particles to settle· out.
65. Deep-relee.se reservoirs reduce the transport of most sus-
pended POM to toe stream below. Settling and decomposition in the
reservoir may .remove 70 tc· 90 per t!ent of tbe particulate organic matter
introdut:e6. from the watershed (Lind 1971; Armitage 1977). Most
24
•
.t
·'.
allochthonous organic matter is washed into the reservoir during high
winter or spring f l ows and is subsequently decomposed and transi~rmed
into d.issolved nutrients during the period of SUliiDer stratification
(Webster et al. 1979). The loss. or reduction of this food supply for
bacteria, fungi, and certain macroinvertebrates can reduce the abun-
dance of these organisms in the tailvaters. Density currents with high
levels of POM may flov through reservoi.rs--und.erneath, through, o.r above
the main body of vater--and be discharged into the tailvater, an.d when
this occurs concentration of POM in the tailwater increases.
66. In contrast, surface-release reservoirs tend to incr~ase. the
concentration of POM in the tailvater through the discharge of large
populations o·f sestonic plankton produced in the epilimnio·n of the
reservoir. The amount of plankton received fran the reservoir fluctua-
tes seasonally; it is greatest during peak production periods (turnover)
in spring and fall. Microseston in the effluent of Lake Laurel,
California, vas 85 percent more abundant than that in the infloving
stream (Maciolek and Tunzi. 1968). Filter feeding invertebrates may
floU!"ish below these epilimnetic release reservoirs due to the in-
creased availability of food particles.
67. Concentrations o·f PO.M in tai.lvate.rs below reservoirs vith
short hydraulic residence times may not differ substantially from those
in reservoir inflows. Sho•rt hydraulic residence time does not allow
sufficient time for production of enough phytoplankton or settlement
and decomposition of enough suspended organic matter to significantly
alter the POM concentration received by the tailvater.
Nutrients
68. Minerals and nutrients characteristic of the surr0unding
vaters.hed are carried into streams by surface runoff and tributary
inflow. The amount of nutrients made available t:> a reservoir depe·nds
on the nature of the soil, amount of rainfall, l o cal agricultural
practices, and domestic and industrial sevage inputs . Significant
short-term increases in minerals ~~d nutrients during periods of
intense runoff are cl~acteristic of unaltered streams; whereas waters
relee.3ed from reservoirs are more uniform in mine·ral and nutrient
25
content (Wirth et al. 1970). Nutrient enrichment of a tailwater is a
funct.ion of the enrichment of the reservoir above, reservoir stratifi-
cation, depth of release, and hydraulic residence time.
69. Stratified reservoirs that have surface outflows trap nutri-·
ents in the deep hypoHmnetic waters (Wright 1968). Total dissolved
solids, nitrogen, and phosphorus concentrations decrease in the epilim-
nion during the summer through the assimilation of these nutrients by
seasonally increased phytoplankton populations. In addition, adsorp-
tion to clay particles and subse~uent settling may reduce phosphorous
concentrations in the epilimnion. Moribund plankton from the epilim-
nion and organic material c:il.rried by the inflowing water continually
set,tle out, enriching the hypolimnion as decomposition and nutrient
transformation takes place.
70. The retention of nutrient rich hypolimnetic water may in-
crease the potential productivity of the reservoir ·(Murphy 1962) ;
however, continual inflows. of dissolved and suspended nutrients may
result in a noticeable deterioration in water quality (Johnson and
'Berst 1965). The . biological productivity of the . tailvater below a
stratified surface-release reservoir is reduced during .tbe summer
because of the decrease of dissolved nutrients in the discharge. In
tbe fe.ll, however, after the reservoir becom.es vertically mixed and
nutrients are uniformly distributed ?.n the water column, the avail-
ability of nutrients in the tailvater is increased and productivity
improved.
71. Deep-release reservoirs discharge the nutrients which accumu-
late in the hypolimnion during stratification. The reduced oxygen
concentration, resulting from decomposition, enhances the accumulation
of diEsolved nutrients (Hannan and Young 1974). As a result, more
nutr~ents are discharged from the hypolimnion in the form of readily
usable ammonia and dissolved phosphate. The release of clear, nutrient-
rich water, more fertile than that released from the surface, often
results in increased productivity in the t .ailvater. Objectionable
taste, odor, and excessive algal production are often associated with
' these releases. Dense algal mats, sometimes established below these
26
J
...
~ ...
...... · ..
•• 't .~
. '
; .
·.
reservoirs as a result of the increased nutrienta, are usually asso-
ciated vi th incre&sed numbers of invertebrates, providing a food base
for tailwater fish. Increased algal growth and the subsequent increases
in mac.roinvertebrates can aid in the establlshment of a trout fishery
(Pfitzer 1954).
Reduced compounds in tallwaters
72. Hypolimnetic discharges may contain high concentrations of
reduced iron, mangane.se, sulfur, and ammon.ia produced by natural ly
occurring anaerobic processes. High concentrations of these materials
may be toxic to tailvater biota, or affect certain life stages at
sublethal levels (Lehmkuhl 1979). Dissolution of these substances fraa
the soil and decomposed organic matter occurs in the reservoir vhen the
hypolimnion becomes anaerobic and the redox potential is !overed. A
combination of these elements may have a synergistic effect, so that no
one element or compound is solely responsible for toxicity to the biota
(J. M. G~izzle, Auburn University, unpublished manuscript). There-
lease of anoxic hypolimne~ic water may produce combinations of toxic
elements that normally vould not be present in una.l tered streams c;;,r in.-~ .. .. . . • ~
.• . ~~;·~ .. ,. •....._
epilimnetic release tailvaters. ~-:-"'""
73. Iron and manganese. Soluble reduced forms of iron and man-
ganese begin to oxidize upon release from the reservoir and precipitate
in the form of ferric a·nd manganic hydroxides that may stain concrete
and rock surface·s in the tailvaters. These poorly solubLe hydrous
metal oxides are a nuisance to dovnstream munic ipal water treatment
plants . Deposits of these hydro·xides on the substrate below hypolim-
netic release reservoirs may also af.fect the numbers and: types of
organisms present. However, the effects of these deposits have not
been sufficiently documented (Krenkel et al. 1979).
74 . Iron concentrations in neutral or alkaline waters usually
range from 0.05 to 0.20 mg/1 (StW!DD and Lee 1960). The highest accept-
able concentrations of iron are 0.30 mg/1 in domestic water supplie• and
1.00 mg/1 for treshvater a.quatic life (U. S. Enviromnental Protection
Agency 1976).
27
··~ -·-· -···------···--·-----,
.......
1
75. The chemical characteristics of manganese are similar to
those of iron; however. manganese has a slower ox1dat.ion rate and forms
more soluble salts than iron. Manganese concentrations are not as
effectively eliminated from the water column by precipitation (Wetzel
1975). Soluble forms of manganese are therefore more persistent in
tailwaters. Below stratified deep-release reservoirs, manganese con-
, centrations may exceed l mg/1, which is greater t 'han concentrations
found in most freshwater environments (Churchill 1958; Martin and
Stroud 1973). Concentrations less than 50 ug/1 have been found to
inhibit green and blue-green algae in streams and to favor diatoms
(Wetzel 1975).
76. Hydrogen sulfide . Occurrence of hydrogen sulfide in bypolim-
netic discharges is the result of the anaerobic bacterial decomposition
of organic sulfur compounds and th.e reduction of sulfates to sulfides
vi thin the reservoir. Hydrogen sulfid·e concentrations are highest and
most toxic under acidic conditions (low pH). In neutral or alkaline
waters • the sulfides combine with iron, forming insoluble ferrou.s
sul~ide 9 which precipitates from the water. Thus, hydrogen sulfid~
· appears ·only when pH is low and oXygen content. is near zero. or when
all available iron has been precipitated from neutral or alkaline water
(Syoons et al. 1964).
77 . Discharges with hydrogen sulfide concentrations above 0.002
mg/1 have a!'l. objectionable odor and may re,sult in fish kills and in a
reduction in diversity of benthos and algae. Smith et al. (194~)
reported a 72-hour Lc 50 of 0.019 D.g/1 for bluegill eggs at 2l.9°C and
a 96-bour tc 50 0.045 mg/1 for adult bluegills a:t l9.6-20.3°C. Fish
die-offs a n d adverse benthic responses have been attributed to high
levels of hydrogen sulfide (Wright 1968).
78. A.'!l!!lonia . Ammonia nitrogen (NH 3-N) is a by-produc·':. of organic
decomposition (Cole 1975). In some situations, depending on the pH of
the water, NH 3 may be toxic to living organisms. Concentration of NH 3
increases as pH increases, and NH 3 is most toxic when 'botb dissolved
oxyge.n and carbon dioxide levels are low (Boyd 1979). Toxicity is also
affected by temperature and alkalinit.y (Lloyd and Herbert 1960).
28
,
.,· ..
'
·'
··-
·' .·
Concentrations betveen 0.6 and 2.0 mg/1 are lethal to fish after short-
term exposure (European Inland Fishery Commission 1973, in Boyd 1979).
Pathological changes in fish organs and tissues have been noted after
continuous exposure to sublethal concentrations between 0.006 and 0.34
mg/1 (Smith and Piper 1975, in Boyd 1979).
79. In late summer OF early fall, the concentration of 1m 3 in-
creases in the anoxic hypolimnion of stratified reservoirs as the
result of extensive anaerobic decompgsition of organic matter. Addi-
tional JR3 may be released from the bottan sediments or may be. carried
into the hypolimnion by density currents {Hannan 1979). Consequently,
81:11110nia concentrations in tailwaters below hypolimnetic release dams
tend to increase during late summer or early fall. Ammonia concentra-
tions also increase in tailwaters below epilimnetic release dams during
fall, after the fa.ll overturn.
. '
29
. .. .. •
...
PART V: METABOLISM AND TROPHIC STRUCTURE
80. The assemblage of organisms living in a particular reach of a
tail~~ter may be considered a biotic community. In this community, the
interactions between the various types of organisms (i.e., primary
producers; primary, secondary, and tertiary consumers, etc.) are based
primarily on their nutritional requirements and feeding habits . The
canplex nutritional and energy cycle that results from this interaction
is often referred. to as the trophic system, within which each type of
organism occupies a particular level.
81. Energy enters the tailvater trophic system in the form of
light energy and nutrients and detritus. These materials are used by
the primary producers and consumers that make up the lover trophic
levels of the system. Energy is progressively transferred upward
through the system· when the organisms in these love.r trophic levels are
eaten by the secondary and tertiary consumers that mak.e up the higher
trophic· lc·;els •
• !, .. .'.;; ·~
.. , . 82. As the energy is transferred from one level to another,
• 4 ·~ • -
lo~ses result from the partial use of the available energy requir~d for '
maintenance and reproduction. Generally, each successive trophic level
contains only about 10 percent of t he energy available to the preceding
one (Russell-Hunter 1970). The net result is that only a small .per-
centage of the original energy is available at the highest trophic ·.
level. Greater biomass production at the primary level, enabled -by ·
increased input (e.g., primary production, detritus), usually results
in greater biomass production at the highest trophic level (Bovee 1975).
Streams
83. In streams, metabolic essentials are not recycled and must be
constantly supplied from upstream sources or streamside vegetation.
Metabolic activity and productivity are addi.tionally governed by the
composition and sources of the nutrients entering the stream and how
efficiently thP.y are utilized.
30
I
...
·'·
·.
.-'··
.. ,
84. Stream organisms take up, transfonn, use and release organic
materials, thus acting as processors of the organic material passing
through the• system (Fisher 1977). Fish, the largest organisms in the
stream community, us.ually represent the top level of the food chain.
Their abundance reflects the quantity of primary and secondary produc-
tion that takes place in lover levels of the trophic system.
85. The organic content of a natural stream system comes from
allochthonous and autochthonous sources.. The metaboli sm for both
sources is based on the supply of detritus vhich is used as food by
de·tritivores and omnivores. and furnishes dissolved nutrients to the
primary producers. An allochthonous system (heterotrophy) is based
primarily on organic material that is carried into the system from the
vatershed. Autochthonous systems (autotrophy) derive their energy ~ram
photosynthesis that takes place in the streambed. These systems are
most representative of slaver flovs, vhich enable a buildup of peri-
phytic vegetation and, occasionally, vascular plants.
86. In contrast to the source of organic materials in most
ecosystems. tbat in streams is d~rived primarily from allochthonous
sources (H~es. 1970; Cummins 1974). A headvater stream, for example,
may derive 99 percent of its energy inflov from allochthonous origins
and the remaining 1 percent from photosynthesis (Fisher and Likens
1973; Cummins 1974). Higher order streams may also depend on alloch-
thonous sources of energy .
87. As much as 60 percent of the total organic matter taken into
the• stream from allochthonous sources may be in the form or leaf litter
(Cummins 1974). Additional allochthonous materials may be in the form .,
of twig~ and shoreline debris or dissolved nutrients from·vatersbed
runoff. Leaf material may be found in suspension in the stream or
deposited on the stre9JIIbed (Minshall 1967). The leaves are rapidly
colonized by fungi and bacteria, vhich aid in p rocessing the material
.into fine particles and dissolved organic matter . The dissolved
nutrients released duri.ng decomposition are then available for u_se 'by
primary producers . The colonizing fungi a nd bacteria are in turn used
as food by the shredding and scraping invertebrates that are involved
31
··-
...
in 'the mechanical aspects of leaf decomposition. The fungi and bacte-
ria may be the primary source of nourishment for these invertebrates,
since some leaves have been shown to be of little food value. These
invertebrates, in turn, make up the primary prey of predators in the
higher levels of the trophic system ( CUIIIIlins 1974).
88. The structure and complexity of the benthic community may ..
change vith the amount and variety of plant detritw~ present in the
system (Egglishav 1969; Mackay and Kalff 1969). As the organic material
breaks down, the variety of food becomes more diversified, producing a
similar response in the invertebrate community. Seasonal shifts in the
diversity of the stream invertebrates are related to changes in food
supply and othe.r natural changes during the life cycle of the organisms
(Mackay and Kalff 1969).
89. Since many aquatic invertebrates are able to process organic
matter at lov temperatures, much of the organic material in streams is
used during fall and winter . Hovever, not all of the organic matter
entering the systec during fall is used. Sane of the material is
stored in the slover depositional zones o~ the s 1tream, vhere it remains
·"·'"'· ... .. .. · · until used by the stream biota. These zones act as energy reservoirs
and help maintain the biota annually. Material in depositional .. ~one15 .· ·
may be re.distributed during flooding. This redistribution may be
important in slov-vate·r zones, in r ·educing the occurrence of oxygen
deficienc.ies that could develop during extended periods of reduced
flov.
90. Autotrophic production varies as a result of differing envi-
ronmental situations (e.g., changes in shading, turbidity, water
velocity, and water chemistry). Autotrophic production is greatest in
streams with little shading from streamside vege·tation, and in small
streams in forested areas before and after formation of a lellf' c.anopy
(spring e.nd fall). Photosynthetic acti.vity is greatly reduced in
heavily shaded streams, even vhen adequate amounts or nutrients are
available.
91. Autotrophy may be the major contributor to the energy budget
or large rivers or sm.all uncanopied streams (Minshall 1978). Removal
32
t
·•
••
...
·'
·.
of a canopy results in a shi.ft from a heterotrophic to an autotrophic
system~ as stream temperature and photosynthetic production both
increase {Gelroth and Marzolf 1978). Photosynthetic activity by
periphytic ·algae takes place primarily in shallov~ well-oxygenated, and
vell-lit stream bottoms. The periphyton is usually the first auto-
trophic component to become established in a stream, and is most preva-
lent where flows are least variable. Phytoplankton become dominant in
rivers and large streams where depth and turbidity inhibit benthic
production by the attached algae {Fisher and Carpenter 1976).
92. Faster current velocity in riffle areas, as opposed to pools,
results in increased rates of net primary productivity (Kevern and Ball
1965). Steep diffusion gradients between plants and available nu,trieata
are formed in the fast-flowing water, allowing for more rapid assimila-
tion of vi tal substances by the· attached algae or macrophytes. Because
of these steep diffusion gradients, many algal species grow best in
swift currents {>15 em/sec) (Whiteford 1960). Phosphorus uptake may be
over 10 times greater and respiration over 70 percent greater in swift
water {18 em/sec) than in still water (Whitford and Schumacher 1961). • ·\ .. -.:"":·!:
93. Dense, fel tlike, dark green or brownish communities, con..:·· .~.
sisting mostly of diatoms, may be established in streams vi th svi.ft
curreats (Mcintire 1966). Diatoms such as Ganchonema, Diatoma, or
Navicula, which require high light intensities and solid substrates,
are co~~~nonly found in swift streams in association with filamentous
algae such as Cladochora . The accumulation of attached algae on gravel
and rubble is more rapid in fast currents, but the growth stabilizes
after a time and the total biomass per unit area is similar to that ia
slower c.urrents. However, higher productivity is maintained in the
faster current, allowing a greater export of biomass (Mcintire 1966).
94. Slow currents {<15 em/sec) may allow associations of green
filamentous algae (including Stigeoclonium, Oedogonium, and Tr i bonema)
to develop {Mcintire 1966). These associations appear as bright .green
aggregations similar to those found in ponds. Concentrations of
organic matter are usually higher in streams dominated by green algae
than in those dominated by diatoms. Conversion from a diatom-moss
33
.. · .
j
assoc.iation to a c011111unity of filamentous green a.l.gae (possibly
associated vi th rooted aquatic macrophytes or diat.oms) may indicate a
shift to a more autotrophic stream syst~ (Cummins 1974).
95. Macrophytic vegetation develops in streams where flovs are
relatively stable. This vegetation is seldom consumed and therefore
does not directly contribute to higher trophic levels while alive
(Cm:!mins et al. 1973~ r."ishe.r and Carpenter 1976), although they may
serve as a surface for periphyton. However, when the vegetation dies
'Uld decomposes, it contributes organic matter to the syste;m. St.re.ams
subject to severe changes in flows physically limit the development of
significant plant growth. Additionally, these plants are not found
'where insolation to the stream is low or where the vater is relatively
deep and turbid.
Tail waters
96. A variety of types of organic matter, leaves, POM, algae,
·'etc :~ must be present in the stream to maintain ecosystem diversity :·
. -:(CUIIIIlins 1972). However, reservoirs · act as particle traps, interfering
vith the passage of detritus into the tailvater. As a result, detrital
material from the watershed, important in energy transformation in
natural streams, is largely unavailable to a tail water system.
97. Nut .rient material present in the clear disc.harges of bypolim-
netic release reservoirs is primarily in a d.issolved state as a result
of decompositi.on by-products that accunulate in the bypolimnion. (Odum
1971). Water d.ischarged from the .hypolimnion may be more fertile than
that from the epilimnion because of the concentration of these dis-
solv.ed nutrients in the deep vater.
98. Tailwaters immediately below hypoltmnetic release dams are
autotrophic because concentrations of dissolved nutrients are increased
and turbidity is decreased. The clear, nutrient-rich discharges are
particularly important in tailvaters with stabilized f1ovs because they
facilitate the production of dense algal growths (Stober 1963; Ward
1976b). However, as the water moves farther downstream, conditions
34
-
•
••
..
-'
•••
(i.e. • increased turbid~-ty, reduced nutrient availability) become -less
conducive to algal production,. The gradual increase in the detritus
load due to allochthonous input results in a rev~rsion of th~ tailvater
to a heterotrophic condition in vhich the algal community plays only a
relatively l~ited role. It may. therefore. be possible for a section
of stream belov a reservoir to shift from an autotrophic system in the
i.Dmediate tailvater area to a heterotrophic system downstream. vi th ·'-0
area of transition in betveen.
99. Tvo genera of filamentous green algae, Clado~hora and
Ulothrix, are commonly found belov deep-release reservoirs (Stober 1963;
Ward 1976b). Mats of Clado~hora vere located in riffles in the first
9.6 km below Tiber Reservoir. Montana (Stober 1963). The for.u.tion of
these algal mats may physically inhibit the production of the oost
desirable fish food organisms but may attract othe-r taxa (Wel~h i96~; ·. ·
Ward 1976.b). The algal mats may act as barriers to organisms thFt.t ·
require deeper substrates for completion of their life cyclP.s (Armitaae
1976).
100. Water discharged from surface-release reservoirs, vbet~
stratified or not, may contain s,ignificant amounts of plant debris an4 ..
detritus, but the primary source of organic matter in the tailvater is
plankton produced in the reservoir. Plankton can be used directly by
secondary consumers in the tailvater or, after de3.th and decomposition,
may add to the particulate organic matter that is available to both
primary and secondary consumers. Thus, most surface disc barges from
reservoirs supply particulate organic matter to tailvaters, and deep
discharges supply dissolved organic matter.
101. Phytoplankton uu.y occur in zones of the tailvater vhere the
vater velocity is reduced and the str~ambed vid~ned, and adequate
nutrients are available. Hovever, phytoplankton numbers decrease as
the vater flovs farther downstream because of depletion of nutrients,
increased turbidity, and simple mechanical dest-ruction (H~rt~ e.nd
Himes 1961).
102. Storage of infloving vater for extended periods (e.g., as in
flood control reservoirs), accompanied by reduced downstream releases,
35
. _,.
-........ ~ ... ··
I 'I ..
I J
may result in bank stabili.z.ation and ~be eventual establisl:Dent of
strea::tside vegetation in tailwater reacbe.s. Streamside vegets.tion in
these e.reas increases both the bJilount of shade and the quantity of
allochthonous materials in +he tail water. The establishment of macro-
phytic vegetation BnJ periphytic algal growths are also enhanced vben
stabilized flovs are accompanied by reduced tur'bidities (Wa...•d l976b).
103. M1.lllagement schemes for some reservoirs require that dis-
charges be released at irregular intervals. For example, releases frOID
flood control reservoirs may be erratic, since they usually depend o.n
duration and amount of rainfall in the waterst.ed. These flov irregu-
·larities result in a brief buildup of detrital. material in the
str~ambed of the tailvater during minimum re1eases. The subsequent
relee.se of runoff vaters from the res~1w~ir may scour the tai.vater,
resulting in a physical disruption and alteration of the stream simi1ar
t~ that in a natural stream after a heavy rainfall (~otzky 1971). The
periodic releases may sveep the streambed free of accumulations of leaf
li~ter and detritus deposited by adjacent s t reamside vegetation (Ward
1976b): The tailvater is thus denied an important source of ·.energy
-1·-# • i ..
~Radford and Hartlar.1-Rove 1971).
104. In tailvaters subject to daily variations in vater release
(e.g., peak pover hydropower facilities), detritus and sediment are
cons't.antly flushed avay (Ward l976a). Enrichment vitb perticulate
organic matter is !llargi.nal at best, part.fcularly near the dam, and
the lack o~ detritus places further stress on the trophic structure
of these waters. Fluctuations in vater level increase streambed and
bank erosion thereby increasing turbidity and discouraging the estab-
lishment of s~reambanY. v~getation and streAmbed algal growth. These
cor:-i ... t.i ons may critically lit:~it the tailvater biota, 'which might other-
vise c.hrive.
105 . Te.ilvaters are highly modified environments that may be
subject to extreme conditions not normally found in natural streams.
Be~ause of these modifications, the tailvater biota may be disrupted vr
enhanced. Either development vill result in the creation of a trophic
structure ~uch different f r om that normally found in an unaltered stream .
36
•
•
•
: ...
.. .
.. -. ·•'.'•;.
•,
'·
PART VI : AQUATIC I!fVER'1'EBRATE IN TAILWATERS
Invertebrate Ecology
Streams
lo6. Benthic stream Ca!IIIIUllities are extremely dy'namic and are com-
posed of a large number of species (Patrick 1970). Many have intricate
life cycles adapted for survival in the changing environment found in
most streams (Brusven et al. 1976). Their life cycles are characterized
by short generation times, high reproductive potentials, and reduced,
body sizes (Patrick 1970). The adults of most important stream insects
are terrestrial, short-lived, and con.cerned only vi th breeding and
dispersal (Hynes 1970).
107. The bottom fauna is not randomly scattered and its distribu-
tion results from interaction of the invertebrate's habitat requirement•
with the varying environmental conditions that exist in different areas
of the stream (All.en 1959). The mosaic pattern of distribution ex-. . .. ,..•.:,
hibit~d b,y benthic 'organisms is pri~ily determined by cur'rent veloc-· · ·
ity, substrate•.type, and food availability (Ward 1976a; Minshall and
Minshall 1977). In addition, temporal and spatial temperature differ-
ences affect the presence of both individual species and life stages.
Temporary colonization of microhabitats produced by changes in these
variables increases the taxonomic diversity of the stream benthos 'and
ensures a year-rour.d food supply for fish (Ward 1976b). Outside inter-
ferences (e.g., pollution, ilt.pound:nent) in a stream system tend to
red'Uce the benthic diversity as a result of the reduced diversification ··
of available microhabitats (Ward 1976a).
108. ~ Current velocity ma.y h-ave the most influence on the
regulation of invertebrate distribution and abundance, especially at
specific sites in the stream (Chutter 1969; Giger 19i3). Hovever, the
influence of current velocity on invertebrate densities in different
sections of the stream may be masked by the effects of other variables
(Chutter 1969). Some stream organislllS have morphologic:::a.l respirator;y
and feeding demands that require them to position themselves in floving
37
....
water (Ward 1976a). As long as the stream velocity remains relatively
high~ and the supply of food and oxygen is adequate, these organisms can
survive (Bovee 1975). However, life stages adapted to fast water d.ie
vhen subjected to slov current and reduced oxygen because they are phys-
iol.:>gically unable to adjust to the altered conditions. Relatively high
stream velocities are required to ventilate the delicate gills of these
organisms and they must be exposed to the current (Gig~r l973t Armitage
1976). In· addition, filter-feeding i ·nsects are deprived of food if the'"
current fails to carry materials into their food-gathering nets .
109. Many stream organisms move about in a "boundary layer" or
dead-water zone (up to 1 mm in thickness) near the interface of the
substrate and vater vhere current velocities are substantially reduced
( AI!Iouhl 1959; Ward 1976a). The boundary layers and dead-vater zones
formed in and around substrate components provide many types of habitat
and locations for invertebrates. Rough substrates result in an increase
in thickness of these boundary layers and a tendency tovard ~re rapid
reduction in the current velocity (Bovee 1975).
110. Strong stream currents discourage t'ree-sYiJIIIling invertebrates.
Insects living in the svift-vater areas 'are .;;phologically modified· to
vi thstand the mechanical forces of the· current. Most adaptations enable
insects to avoid many of the adverse effects of strong currents by
kee~ing their bodies avay from the force of the flov (Hynes 1970).
Fusiform, flattened, and streamlined bodies aid survival in swift
currents by enabling insects to "crouch" in the boundary layer. Because
morphological modifications force them to face upstream, most voluntary
movei:~ent is upstream (Hynes 1970). Temporary attachment structures are
common adaptations that enable insects to release and reattach them-
selves after a period of uncontrolled movement in the current. Some
organisms construct c.ases of small stones, detritus, or silk that are
anchored firmly to the substrate. These organisms catch organic
particles frO!:l the water by either m~ing morphological filtering
mechanisms or constructing nets.
111. Reduced current velocities li:ni t the abundance and diversity
of "svift-vater invertebrate connuni ties, either physically because of
38
•
•
••
. . --...
... .....
:: ..... ,
•
....
siltation or physi.ologica.lly because of inadequate oxygen and nutrient
exchange (Giger 1973). An extreme reduction in current eliminates
species that are dependent on flov for respiration and food procurement
(Sprules 1947) .
112. Freshets, flov cessation, riffle sedi.mentation, water level
nuctuations, and unstable substrates .result in changes in the species
composition and may catastrophically reduce the stream fauna (Sprules
1947; Peterson 1977). Severe floods and spates scour and flush insects
from the streambed, leaving only the species able to vithstand the in-
creased flovs (Hynes 1970). Scouring may reduce the numbers of insects
in a particular section of·a stream by 50 percent (Sprules 1947).
113. Spates that scour the stream substrate result in temporary
dislocation and dispersal of invertebrates, but the density and struc-
ture of the COIIIIIIWli ty may recover to pre flood conditions vi thin 30 days
if the insects are not dispersed over great distances. After seven
floods in Big Buffalo Creek, Missouri, the structure of the in.vertebrate
riffle community vas very similar to that found in the same location
bet'o·re the floods (Ryck 1976). Apparently, enough organisms are left
after spates or. other disturbances to repopulate the stream section.
They escape the ef.fects of the disturbances by maintaining themselves
in the protected areas of the stream vhere flov is reduced (Patrick
1970) •
114. Most stream organisms are protected from the effects of
severe flooding and relatively short periods of devater~ng because they
·<:::· .: .. ::~· .. ··· .. are imbedded in the upper 15 to 22 c:n of the gravel substrate (Hynes
.. , .. 1974). The movement o·f trichopterans into deeper strata of the strella
. bottom may be indicative of their response to scouring or to inc;eased
sediment loads that accompany flood waters (Poole and Stewart 1976}.
.... ....
In addition, extended hatching periods and firmly attached e.ggs also
en.sure that certai.n species are not eliminated during: str~am distur-
bances (Hynes 1970). The repopulation of a riffle sections is probably
a result of a combination of several factors, including downstream drift,
upstream larval movement, ar.u upstream <:gg-laying. flights of adults
(Ryck 1976).
39
: ··•···
.•
115. Substrate tYDe. In most streams, pools and riffles form the
most _distinctive types of habitat. Formation of pools and riffles is a
combined process of dispersion and sorting of the bottan materia.ls.
Pools are ·associated vi th stream bends, and riffles vi th crossings and
inflections in the streambed. Fine particles are washed away from
riffles and deposited in pools, leaving only the larger graYels and
rubble in the riffle area (Yang 1971). Ri.ff.l:es provide optimal environ-
mental conditions for many species and are diverse, productive inverte-
brate habitats. Invertebrates produced in riffles may pott:ntially be
swept into the pools, where they are likely to 'be eaten by fish
(Peterson 1977). More insects are usually produced in riffles than in
pools or on bedrock or submerged vegetation because current velocities
are higher in riffles and rubble substrates incre.ase the availS:bili ty
and number of microhabitats. Insects inhabiting the· pool areas are .
similar to those found in ponds and lakes and feed on the ac.cumulation
of organic matter that forms sediment (Krumholz and Neff 1970; CUDIIlins
1972).
}-~·· 116. Intermediate zones, which may oc.cur between stream riffles ·
----and pools, a~e called "runs" (Luedtke et al. 1976.). ·:These are ~s of.
moderate flow over relatively shallow stretches of ·the stream and may
be depositional or erosional, depending on. the current velocity. The
identity and abundance of benthic fauna present are determined by
whether the area' is in a depositional or erosional :.one. · .
. ll7. The benthic fauna associated wit'h specific substrate types
generally forms a well-defined community. Any change in the substrate
results in an accompanying change in invertebrate species (Sprules
1947; DeMa.rch 1976). Lar,ge rubble (45-70 111111 in diameter) has a variety
of microhabitats, which me.y be inhabited by all sizes of insects. This
type o:f subs,tre.te is found in swiftly !'loving areas of strE!ams where
smalle.r sized substrate materials are vashed away. The organisms
found here are ada-pted to living in habit-ats that offer reduced contact
with the current ( CUIIIIIlins 1966). Invertebrates able t .o survive in
small-particle ( 5-25 JIID) substrates are, by necessity, small and
4o
•
.•.
'.
.. . ...... ~. . •·. . . · .
~-=·.. ...
•.
........
. . '
'
resilient (Sprules 1947). Their microhabitats ar~ commonly des1.royed·
or altered during high, irregular flows.
118. Manipulations of streamflow may alter the detrit~U "trap"
capacity of the substrate and ultimately affect species composition and
stream productivity. Small detrital particles and silt tend to accumu-
late excessively in the interstices of small-particle aubst.rates,
·whereas in rubble habitats the interstices are swept cl.eao by the
current. As a result, many a.quatic insects prefer substrates composed
of moderately si.zed ( 25-45 mm) particles because they serve as a better
benthic food trap without reducing habitat diversit~r (Rabeni and
M:Lnsball 1977) .
119. Some species of insects are able to take advantage of in-.
creaaed sedimentation, but usually suspended and settled sedimeotl
adversely affect the invertebrate population. At lov flows and reduced
current velocities, silt and sand seal the interstices in a rubble
substrate. This sealing restricts access to the undersurfaces of the
ston.es and generally reduces the !lumber of usable habitats. The sedi-
..
• ! • .. ... .. ... ........ ..--• •. .-\ -· ·.. ··~"-ifi:·s.l:::.
ment ·is ttasily displaced into suspension at higher . flows and settles · .,;
out in deposi tiona! zones where flows are reduced. The problems :.
caused by sediments are sometimes lessened by the development of car-
.pets of algae over the streambed, which r:ur.y replace microhabitats
filled in with sediment (Brusven and Prather 1974'}: · .. · ··
......
120. Macroinvertebrates apparently migrate out of areas exposed
to heavy sediment loacs. Their response to sedimentation is rapid, and
only a fev days are required for numbers to decrease signi.ficantly.
Conversely, their response to a decreas.e in sedimentation results in a .....
·.rapid recovery of the c011111uni ty. Sandy substrates are generally un-
suitable for insect production because of the instability of the sand
particles and the thinness of the protective "boundary layer." Up-
st.ream movement of riffle insects in sandy areas is generally prE:cluded
by the effects ot current on the fine, loosely compacted sediments. L:w
current velocities and rubble substrate facilitate upstream movement of ·
invertebrates (Leudtke and Brusven 1976) •
41
· 121. ~ A mature stream. ecosystem is highly diverse, and
includes complex food webs (Krl.DDholz and. Beff 1970). The increased.
ccaplexi ty of links. in the food veb increases the chances of survival
of the stream community. A fluctuating autochthonous food supply
'supplemented by allochthonous nutrients increa.ses survival because . -
species are not restricted to a single food item (Russell-Hunter 1970).
122. Although benthic crustaceans, mollusks, and other small
invertebrate life might be present, aquatic life stages of insects are
the most abundant f'orms of primary cons.l.DDers ·in most stre~. Their
diets vary greatly (e.g., the forms represented may include herbivores,
·detritivores, carnivores, and omnivores) and some forms sh:if't from one
source· to another seasonally (Chapman and Demory 1963). A change fran
herbivory in the early insta.rs to ca.rnivory in the later insta.rs is
common (Anderson and C'u:Dmlins 1979) .
123. Food gathering and the a.ss-:>ciated morphological and. be-
havioral adaptations are the most important functions of' animal con-
sumer& in a lotic system (Cummins 1972). Food ha~its are more closely
related to the size of the organism than ~o :~e species. Most·early
.. 'lite stages ~d small-sized insect's'.f'eed primarily on ·detrital can-:·''·
ponents (Cummins 1972). Aquatic in.:.;•!cts. are opportunistic and are able
to adJust to differing availabilities of food; very fev are strictly
he.rbivores or strictly carnivores. Minshall (1967) noted the presence
in a small benthic community of 14 percent herbivores, 3 percen.t
carnivores, and 83 percent omnivores. Food availability is gene·rally
not a. limiting factor for mobile stream organisms because they are
able to actively seek food (Krumholz and Nef'f 1970).
124. Macrophytic coi:IIIIunities often shelte.r larger a .nd more varied
populations of invertebrates vben they are composed of plants with
finely divided leaves, rather than plants. with simple leaves. Herbi-
vores harvest peripbyton from. the surface of the leaves and use the
m~o:.~ of' vegetation for s'hel ter and protection (Harrod 1964).
125. The riffles may provide a. numbe.r of diYerse foods for inve.r-
tebra.tes, ranging from plant detritus lodged under stones to cl.umps of
algae and moss associated vi th the stream bottom. The accompanying
42
. .
...
·' ..
------
invertebrate communities may differ greatly aaong the various types of
food sources (Egglishaw 1969).
126. The food base of invertebrates living in slow-water areas or
pools primarily depends on the depos.ition of detrital material washed
in fran up·stream. Water in pools may be too turbid and the current too
slov to allow the establishment of sufficient benthic algal growths,
and too deep to allow the development of' signifi,cant quanti ties of
macrophytes.
127. The ·aquatic insect component of the stream benthos has been
classified into four feeding t;rpes: shredders, scrapers, collectors,
and predators (Cummins 1973). The life cycles of shredder-type aquatic
·· · ,•'· ····· · ·-··insects are closely associated vi th leaf fall in autumn. Most of their
.. _ ..
. . ~ ..,. -·.
·'• .
.• ';"·· "" growth and . d:evelopm.ent occurs during late fall and winter. These
organisms are able to adjust their growth rates to the relative avail-
ability and quality of t'ood. Observations on shredders have indicated
a positive selection of leaf material that is heavily colonized by
. microorganisms, both on the surface and throughout the matrix of the
~ leaf particle {Anderson and Cumains 1979) . . . · · _:.;;· ·:;..;,;~-· . .
128. Scrupers are dependent on the production of an autochthonous · -~ ,~
food source from vh.ich they 11 terally "scrape away" required food
particles . The nutriti~nal content of this potential food source
(mostly algae) is much higher than t .hat of a detrital food source
(Coffman et al. 1971) • These organisms are most often. in the
_.-, ..• .-.--mainstream channel, where the dominant foods are diatoms and fila-
. ...... , ... -
•
.::..-.;.~.-~"··~.: .. mentous green algae ( Cum!ri.1s 1972) .
129. Collectors filter fine particulate org~~ic material contain-
ing surface colonies of ba~teria and fungi from the stream flow. The
assimilation of nutrients by filter feeders is ineff.icient and much of
the material is passed dOVTlstream, unmodified, wh~re it may be rein-
gested by other organisms • This process results in a type of unidirec-
tiona! "spiralling" cycle in which many organisms, each feeding on
different components, are able to utilize !'ilterable organic material.
Without this filter-feeding commun i ty, mu ch of the suspended organic
material would pass through the system unused (Wallace et al. 1977).
. ....
130. Predatory insects have high assimilation efficiences,
largely because the nutritional quality of their prey is very high.
However, the quantity of prey may vary and i s usually limiting
(Anderson and Cummins 1979}.
131. Feedi~6 habits partly determine the location and limit the
presence of invertebrate types in a stream. Filter feeders 11 ve in
moving water with a seston load, scrapers in areas where algal growth
is most apt to become established, shredders in areas of leaf litter
and detrital accumulation, and predators in any or al.l of the available
feeding locations, depending on the abundance of the potential prey
·population.
132. Temperature. Diurnal temperature fluctuations are generally
required for normal growth and de.ve·lopnent of stream insects, whereas
static temperatures are usually disadvantageous (Ward 1976c}. Life
histories of most stream organisms a:~e geared to annual temperature
cycles which synchronize the particular life stages and stimulate
growth (Hynes 1970; Gore 1977}. Triggering mechanisms for excystment,
.· .
encystment, and other vital dP.velopmental processes may not be stimu-
l ated when temperatures remain unchanged; differences of a .few degrees
affect developmental times and durations.. Higher temperatures are
accompanied by reduced concentrations of dissolve.d oxygen and increased
metabolic demands, and cool tempera.tures produce a metabol ic slovdown
(Bovee 1975}. The absence of a certain species from a stream section
may result from one of the specific temperature requirements not being
met. For example, Epeorus sp., a heptageniid ephemeropteran, has been
shovn to require near-freezing temperatures for a certain length of
time for the development of diapausing eggs . Additionally, nevly
hatched nymphs require an extended period (2.5-4 months} of relatively
high temperatures (18-28°C} for normal development and maturity (Britt
1962}.
133. Numbers and biomass of invertebrates in the streambed may
fluctuate .-:-aCJ cal ly because of di f .fering rates of develoJDent and
emergence (F~trick 1962). Invertebrates emerge in the same sequence
each year, but the dates of first emergence and the duration of the
44
'
'
.•.
1 ··,
!
-'i .;
l
·-I
. . :; '• ... ,
•'1 ....... ~..... • ••••• , •••
I
··-····· ..... -..
hatch vary, depending on. water temperatures (Sprules 1947). Insects
may emerge to mate and deposit eggs all year, but the· greatest emergence
takes place during the eveni.ng hours in spring and early summer ( Cbapmao
1966). During emergence, the population of a :particular species in the
stream may be re<iuced to near zero (Hooper 191'3; Brusven et al. 1976).
Alterations in stream temperature during this time may cause an extended
period of oviposition, resulting in seve.ral ages and sizes of nymphs
(Minshall 1968). Competition among the progeny of a species, as well
as between vari.ous insect :;pecies with similar life requirements, may
be partly averted by the stagge.red deposition of eggs and subsequent
d.if'ferences in developmental ratee (Minshall 1968). The early stages
of many aquatic invertebr~tes are small and essentially 'unavailable as
fish t'ood ( Chapman 1966).
134. Densities of insects may vary seasonallY, dependjng on
species composition. In northern temperate ·streams, the benthos
genera:lly reaches a numerical maximum in the fell and earlY winter
· a:rter ,eggs batch ( CUJIIIIlins 1973). Periods oi maximlll.' stream inverte-
brate b .iomass may not occur concurrently vi th the numerical maxima .
The greatest invertebrate biomass genera lly occurs in the spring and
··fall during peaks of growth. The abundance of organisms vith short
life cycles v~ies considerably wi t .h environmental conditions (Patrick
1962). If they reach maturity by fall, additio.nal eggs &re deposited
which undergo development during the winter months (Cummins 1973).
Some species, however, require a full year of development to reach
. ·matut'ity.
135.
......... . .......... .
Environmental stress.
.. ... .. ... ~.
Benthic stream macroinvertebrates
·. . ~·
·have traditionally been good indicators of past a.nd present environ-
mental str ess because of their long life cycles and relatively sedentary
behavior. Changes in c011111unity structure are sensitive indicators of
environmental alterations (Cairns and Dickson 1971). The most sensitive
species are eliminated from the stream, resulting in diminished compe-
. titian among ·the surviving organisms. Only those species able to
tolerate a vi.de range or environmental conditions are able to survive
when l.ife requi.rements become limiting (Bradt 1977).
45
..~ :
136. Short-term expo,sure of tbe stream COIIIIIlWli ty to intolerable
conditions may result. in alteration of the diversity and density of the
fauna. More tolerant species increase in number, because of the lack
of competition, until they reac.h their l .imits of space and food (Cairns
and Dickson 1971}. Additional alteration of an already stressed environ-
ment. will eliminate one or more of the remaining species, resulting in
a major reduction in the standing crop.
Tai~vaters
137. Invertebrate living conditions in a tailvater are different
from those in a natural stream and are dependent prim~rily on the
characteristics of the reservoir discharge. To survive, benthic
organisms must be able to adapt to the changes in primary production
arid the altered physical-chemical characteristics of the tailvater
system (Krumholz and Neff 1970; Jonassen 1975}.
138. The effects of reservoir releases on the downs·tream biota
depend on the type of dam and the subsequent flov patterns, release
depths, and resiliency of the natural st.ream benthos. Macroinverte-
brate species composition and diversity may either be substantially
··enhanced or reduced, depending on the characteristics of the flow in
the tailvater (Ward 1976a}. The benthos belov reservoirs generally
respond to the unnatural conditions vi t .h reduced taxa and increased
numbers· of certain species (Spence and Hynes 197la}. Tailvater in-
sects e.:re ma.l.ler and are considered to be of marginal food value for
fish (Powell 1958; Bauer 1976). The number of species increases
progressively downstream in response to the greater availability and
variety of microhabitats and the presence of increased quanti tie.s of
detritus from streamside vegetation and runoff (Hooper 1973; McGary
and Harp 1973}. However, total numbers of individuals may be highest
near the dam, since systems vi th fev species often are mo.re productive
~~d support a greater biomass than those vith many species.
139. Fe.ctors vhich inhibit be.nthic populations in tailvaters in-
clude alterations in natural yearly temperature changes, isothermal
temperatures, siltation (in some flood-control sites), daily water-level
fluctuations, streambed sc.ouring, reduced concentrat ·on of particulate
46
•
~.
c.,.ganic matter, altered vater quality, and seasonally altered flovs
{Vanicek 1967; Hoffman and Kilambi 1970; Is om 1971; Ward 1976b). Con-\
versely, stabilized novs, decreased turbidities, the introduction of'
seston from the reservoir, increased nutrient availability, and the
grovth of algae and moss increase benthic standin~ crops.
of the inhi.biting and beneficial effects depends on the schedule of
vater release, the vithdraval depth, and the length of time water has
b•!en retained in the reservoir.
140. Fluctuating flovs. High releases fol:oving periods of little
or no flov result in scouring and turbidity, and ~luctuating vater
levels cause increased bed and bank instability {Ward 1976a). Reduced
flovs result in decreases in vetted perimeter, depth, surface a rc ea,
and current velocity. Water temperatures during these periods become
increasingly subject to ambient atmospheric influences {Pfitzer 1962;
War d 1976a). The extreme changes in flov often create conditions that
are unsuitable for most stream benthos. Because of this, invertebrates
are least abWldant in inmediate tailvater areas that are subject to
extreme periodic f'lov fluctuations . Insect densities in the ta.ilwater
may be as much as 30 times less than those of streams floving into the
reservoir {Povell 1958; Trotzky 1971). Hovever, dovnstream moderation
of the effects of flov fluctuatio:1 often results in the gradual in-
crease of invertebrate densities {Radford and Hartland-Rove 1971;
Trotzky and Gregory 1974; Ward 1976b).
141. Continually fluctuating flovs interfere vith the establish-
ment of a stable benthic community because of the preference of various
species for a narrover range of environmental conditions {Pearson et al.
1968). Daily vater level fluctuations generally reduce the production
and standing crop of stream invertebrates by eliminating both the
benthic food base and the benthos (Bovee 1975; Ward 1976a). This
situation is particularly obvious belov hydropover projects vhere
maximtun discharges occur during periods of peak pover demand and
minimum discharges vhen pover demands are lessened. In these instances,
tvo enti.rely different stream habitats are cre&ted. T.he tailvater may
change from a typical pool-riffle association during mini.mum releases
4'j
.
,.
I to a deep, swift stream during maximum rel.eases. Most affected is the
"zone of fluctuation," which is composed of s ,fde channels, backwater
areas, and shallows. These areas alternately undergo the physical
disruption of microhabitats during high flows and dewatering and sub-
strate expoSU!"e during reduced flows. Insects in these areas beccme
disl::"~ciged and physically destroyed during high flows, and they are also
subject to stranding and desiccation during reduced flows (Powell 1958;
Trotzky 1971). In tail waters vi th fluctuating flows, the lack of
permanent, clearly defined pools and riffles precludes the survival of
most stream insects .
142. Some benthic tailwater communities subject to regular, peri-
odic water-level fluctuations may event.uall.y attain a resonable level
of production ( Odum 1969). In these "mature" tail waters • a few s.pecies
(probably two or three) that have adapted to the flow changes make up
the vast majority of the benthic community (Pfitzer 1962). Members of
these benthic communities apparently tolerate brief periods of sub-
strate exposure if it is not severe (Fisher and LaVoy 1972; Ward 19'i6a).
No significant difference was found between numbe·rs of insects li ring
on nonexposed substrates and those living on oocasional_ly exposed
substrates ( 13 percent exposure time) in a "zone of fluctuation" below
a hydropower d.am on the Connecticut River. Massachusetts (Fisher and
LaVoy 1972).
143. Vegetative ~ats act as a refuge for insects in some tail-
waters during brief periods of exposure because of the retention of
moisture in the vegetation. Insects living near the· "mat-rock" inter-
face are more likely to survive than those· found on the surface of the
vegetation (Brusven et al. 1974).
144. Low air temperatures also increase the chan.ces of survival
for organisms stranded in a tailwater and enatle them to tolerate
dewatering for longer periods than during high ~ir temperatures.
Brusven et al. (1974) reported that larvae of chironomids, lepidop-
terans, and trichopterans. could survive dewatering for 48 hours in
cool weather, but that high air temperatur.es and longer exposure
periods resulted in high mortalities .
48
I
I
' I
' I
• I
·~
'
145. In spite of the ability of some insects to survive periodic
exposure., most insect species that inhabit tail waters are found in
the permanently submerged habitats not subject to daily exposure
(Powell 1958; Brusven and Trihey 1978).
146. The lack of flow fluctuation in tailwaters below flood control
reservoirs can disrupt the benthic community. In fact, stable releases
for 3 to 4 week s followed by moderate or extreme discharges .may cause·
mor e stre·ss and mortality to an inse·ct community than the frequent
pulsed releases .found below hydropower dams (Brusven and Tribey 1978).
The stable periods encourage the colonization of the ta:ilwater sub-
strate·, but benthic organisms vhich are not able to adjust to subse-
quent severe flow increases are catastrophically swept downstream.
147. The high seasonal discharges below flood control reservoirs
may also destroy the pool-riffle areas nearest th~ dam and replace
them with an extended "run" section. Farther downstream, however,
pools a~d deep channels may be present which act as buffers to fluc-
tuating water levels and as refuges for invertebratea during periods of
minimal re·leases (Powell 1958).
148. Chironomids are the most resilient group of insects founC: in
unstable areas and are the first to recolonize denuded zones of fluc-
tuation (MacPhee and Brusven 1976). They may be found in association
with oligochaetes, amphipods, and isopods in coldwater tailwaters
subject to rapid water-level fluctuations (Brown et al. 1968). These
invertebrate associations are able to adapt to temporary periods of
exposure by either migrating out of the exposed area or surviving in
the thin layer of water which remains after the stream recedes .
149. Insects most affected by fluctuations i 'n flow are the groups ·
which are generally regarded as quality fish food, including mayflies,
stoneflies, and caddisflies (Powell 1958; MacPhee and Brusven 1976).
Nymphs and larvae of these species are most subject to desiccation, ·.··
since their eggs can usually survive extended periods of exposure. The
number of insects affected by desiccation, therefore, depends on when a
flow reduction occurs and the li:fe stages of the insects present.
Desiccation of the streambed would affect the population drastically
during a. larval hatch, but unhatched eggs may remain relatively un-
affected (Hynes 1958).
150. Stabilized flows. Reservoirs vith stable releases have
relatively stable tailwa.ter substrates (Ward 1976a.). The associated
invertebrate fauna. stabilizes as flows and substrates become more con-
sistent, resulting in reduced niche ove,rla.p and a shif't toward community
equili br:!. um ( Blanz et a.l. 1970; Ward 1976c). Stree.m:flow stability com-
bined vith reduced turbidity may enhance algal and macrophytic growth
and provide additional food niches and microhabitat diversification for
chironooids, oligochaetes, and mollusks (Armitage 1976; Ward 1976a).
The stable environment and predictable .resources tend to eliminate some
species, resulting in a less diverse faunal assemblage with higher
standing crops of the species present (Ward 1976b).
151. In tailwaters subjected to stable seasonal discharges, sedi-
mentation may become limiting to the benthic community. Extended
periods of minimal releases accompanied by moderate detrital and silt
input from rur.off and streamside vegetation effectively .reduce the
av.a.ilable microhabitats. The lack of spates, necessary to flush the
detrital material from the substrate interstices, may event'UI.llly result
in the complete elimination of these productive invertebrate micro-
habitats (Giger 1973).
152. Deen-release reservoirs. Cold water temperatures and poor
water quality (low dissolved oxygen, reduced compounds) often occur in
tai·lwat.ers below deep-release dams. Stratified deep-release reservod:rs
typically produce benthic tailwater communities which are low in
diversity, but which may have high standing crops. This situation i.s
typical of a stressed environment (Ward 1974, 1976c; Young et al. 1976;
Pearson et al. 1968).
153. Modification of the normal temperature regime can affect the
diversity and quantity of the· benthic fauna. several kilometres down-
stream from a. coldwater release dam (Pearson et al. 1968; .Lehmkuhl
1972, 1979; Ward l976c). The overall change in temperatures, coupled
with the delay of seasonal fluctuations, often .results in the elimina-
tion of many invertebrate species from tbe tailwaters. Minimum winter
50
i
...
·. ~··
.. ; !
....
.. ·•.
•
•'
and maximum summer temperatures that would normally provide the thermal
stimulus essential for the initiation of various life history stages of
many stream invertebrates are never reached. Reduced growth efficien-
cies a.t the lowered temperature.s may eliminate species which are unable
to adapt metabolically to abnormally cold summer temperat';.U'es (Hannan
and Young 1974). Alternatively, warm winter temperatures may accelerate
growth rates and result in premature emergence and exposure to air
temperatures that may be lethal or tha.t may complicate the mating pro-
cess (Ward 1976c). These conditions, along with delays in spring
warming and autumn cooling, may prevent the natural hatching and grovth
of insects that have stringent thermal requirements (Lehmkuhll972). ..-
154. The lack of daily fluctuations in vater temperature may
prevent the initiation of egg or larval development (Ward 1976c). Diel
temperat.ure fluctuations in a 24-hour period were as great as l0°C ·in······
an unregulated stream in England, but rarely exceeded 1°C in a regu-
lated section (Armitage 1977) .
. 155. Stresses imposed on aquatic invertebrates below deep-release
reservoirs may also be due to low dissolved oxygen, ·the presence or ·
high concentrations of' H2S and other decomposition by-products, o.r the ·
interaction of these factors (Coutant 1962; Hicks 1964; Young et al.
1976). Reaeration of the vater as it passes through a dam may increase
the concentra.tion of dissolved oxygen to a level tolerable by the tail-
water biota, but the by-products (e.g., iron, manganese, hydrogen
sulfide) of hypolimnetic decomposition may be more persi stent and ha.•re
a detrimental effect on t~ilvater organisms (Coutant 1962). If re-
leases from the r-eservoir are increased, the harmful effects of the
hypolimnetic discharges can be exte.nded downstream.
r .. -.: ••
156. Deep-release reservoirs do not necessarily release water of
poor quality (low or no dissolved oxygen, reduced compounds) but
assuredly produce a new envi ronment which favors coldwater rather than
warmwater organisms (Hoft'ma.n and Kilambi 1970). In st1•atified reser-
voirs where anoxic conditions and pnor water quality do not develop
in the hypolimnion, increas~d concentrations of dissolved nutrients, )
·co2 , and lowered turbidities may favorably affect th~ living conditions
51
of tailvater invertebrates (Penaz et al . 1968). In these circumstances,
the benthic community may have characteris.tics similar to those of
communities in streams vith mild organic enrichment (Spence and Hyne~
197la). •
157. Filterable food ma terial (plankton, some benthic organisms,
and miscellaneous seston) produced in deep-release res~~oirs may be
passed into the tailvaters during periods of' complete vertical mixing.
However, this is not a reliable food source since the plankton and
seston are congregated in the upper strata of most r~servoirs during
stratification and are therefore unava.ilable to the discharge. As a
result, filter-feeding invertebrates are often restricted to dovnstr.eam
tailva~er locations, where discharge effects have been modified and
s.ufficient amounts of filterable material have been int.roduced through
runoff and tributary inflow (Ward 1976b). Plankton and benthos may be
discharged from some deep-release reservoirs during stratification if
the hypolimnion remains oxygenated.
158. Surface-release reservoirs. The downst.ream effects of a
surface-release r;s~noir are usually similar to those produced by a
.·~·~aturai surface-release lake (Ward and Stanfo~d 1979). Water quality
is generally not a problem and tailvater temperatures may only be
moderately influenced in comparision to deep-release sites.
159. Shallow, surface-release reser~oirs can produce abundant
quantities of bottom fau."la and plankton. Invertebrates in the tailvater
may subsequently receive much of their food. in the form of seston and
i~sect.s from the ·reservoir discharge (Walburg et al. 1971). Because of
the rich suspension of food in the rese.rvoir release, filter-feeding
insects, particularly trichopterans, may be extremely abundant in the
tailwater. Generally, the increase jn benthic density is accompanied
by a reduced diversity and the elimination of some species. In
formerly coldwater streams, the release of warm surface water from the
reservoir during summer may result in a reduction or elimination of
certain spE"cies frol!l the tailwater (Fraley 1978; Ward and. Short 1978).
52
· ...
•
••
,•·:-
••
Benthic Invertebrate Drift
Streams
160. Interspecific competition for food a.nd microhabitats may
result in an active downstream movement or "drift" by many benthic
organisms (Waters 1969; Hildebrand 1974). The benthic invertebrate
fauna and the drift i ng fauna are not distinct communi ties. Dr'ift is
merely a temporary e'Vent in the l.ife cycle of most benthic organisms
('Waters 1972).
161. Benthic organisms enter the drift vhen they leave their pro-
tective retreats and are swept downstream by the current. This process
generally occurs a:t night during periods of fee.ding activity (Waters ·
1969). Th~ feeding activity of each species is governed by a diel
pattern based. on photope.riod and is generally initiated at the. same
time each day (Elliott 1967; Waters 1972). The actual movement ·
downstream probably occurs as a series of short hops vith the turbulent
flov assuring frequent contact vi th the substrate. The distance of
passage depends primarily on velocity of flov and the species of inver-.
tebrate involved (Gore 1977).
162. When flovs are suddenly increased, the physical disturba.nce
·of the streambed stimulates a catastrophic-like .response from the
benthos and their p-re ~ence in the drift increases markedly (Elliott
1971; Brusven et al. 1976). The actual nwnber of organisms in the
drift per unit volume remains relatively stable during these periods,
but the ntunbers passing a certain point in the stream ove.r . a period. of ., ..
time may increase significantly (Waters 1969). Natural spates in
streams may disperse organisms over an increased living area or may
displace them into stream environments such as pools and runs,
they find survival difficult and vnere they are more likely to
S\.une.d (Waters 1969). Many benthic organisms die vhen they are
downstream into physically or chemically unacceptable z o nes.
(Russell-Hunter 1970).
vhere
be con-
svept
163. The drift may also be used as a means of escape from
desiccation during low flows (Elliott 1971). Increases in the drift
53
.... ~
•,.
--~· ....
result from a decline in available living space associated with drastic
reductions in streamflow (Minshall and Winger 1968; Armitage 1977; Gore
. 1977). Areas dovnstream, relatively unaffected by reduced flows, may
actually exhibit increased invertebrate populations as ~ result of the
accumulation or organisms from devatered riffle areas (Giger 1973).
164. Recovery of the bottom fauna a~ter streambed exposure or
other catastrophic. events may be rapid ( 19-28 days) after natural con-
ditions return (Herricks and Cairns 1974-76). Drifting organisms from
upstream areas quickly recolonize the affected streambed. Rec.oloni za-
tion of denuded areas may also be aided by a certain amount of upstream
"crawling" movement, which may· replace about 6 percent (by number) of
the dovnstream loss due to drift (Bishop and Hynes 1969) • The renewal
·of drift out of a disrupted area may be delayed until the conmunity
has recovered to a point where the benthic population exceeds the
carrying capacity of the habitat (Dimond 1967). The failure of a
formerly abundant species to repopulate an area after a stream. distur-
:~·"
bance may allow other species to become established, ultimately result-
ing in a shift in community composition and abundance (Waters 1964) •
Ta1lvaters
. _ .. ~~;.~--~
165. Drift in tailwaters is primarily compose.d of organisms from
the reservoir above, particularly below unstratified r ·eservoirs and
reservoirs with surface-release systems. Microcrustaceans and certain
i~sect larvae (e.g., Chaoborus) produced in the reservoir commonly
dominate the teilvater drift (Gibson and Galbraith 1975; Armitage 1977,
1978).
166. Drift of' benthic organisms that live in the tailva.ter occurs
primarily as a result of extreme fL.tctuations in reservoir discharge.
Even species not normally found in the drift (e.g., Chironomidae) may
enter the drift because of these .fluctuations (Brooker and Hemsworth
1978). Increased drift may result in considerable reductions in the
abundance of the stream faun.'!L vi thout actual streambed desiccation
(\Tard 1976a). Repopulation of denuded zones is obviously not possible
from sources upstream, because of the presence of the reservoir. Re-
colonization is therefore dependent on several fa.ctors, including egg
•
•
.,.
. .. . . . ·~-..._. .. ~ -:'. ..... ~ ..
.·
deposition by adult insects which fly upstream, random oviposition of
remai·ning individuals in the denuded zones, and upstream crawling or
svimming by nonaerial invertebrates. Eggs deposited by insect species
which are tolerant to the particular tailvater environment vill develop.
. .
Other species, which are not adapted to the specialized conditions, will
be eliminated.
167. Minimal daily fluctuations and seasonally stable flows may
result in inc.reased benthic populations (Ward 1976a). However, the
stable flows that enhance benthic invertebrate development may reduce
drift. Reduced drift in this instance may be detrimental to fish pro-
duction by limiting the availability of prey (Chapman 1966).
. ~. . ..
168. Terrestrial insects may make a significant contri.buti~n _to ·
available fish food in the taUvater drift; especially in 8.reS:s where
streamside vegetation is abundant (Waters 1964). They may be attracted
to the cool, moist areas of exposed streambeds below reservoirs ~uricg
periods of reduced flows, and vhen discharges are suddenly increased.
they are swept dovnstre9m. vi th the drift (Pfitzer 1962). Since
.\. •""'"":"Y1•: ~ • ·
terrestrial insects-are. most active during daylight, they are mor~
· .. : c.ommonl.y found in the drift during the day -than at night (McClain 1976) •·
ZooPlankton
169. River a:nd stream environments ·are poorly suited for the pro-
duction and maintenance of zooplankton, and they characteristically
harbor small zooplankton populations (Hynes 1970). Their abundance in
,.,_flowing waters is inversely related to the rate of the current. flow.
Thus, the zooplankton present must be supplied to the stream trom
adjacent quiet-water areas or other suitable productive habitats in
t 'he drainage (Hynes 1970).
170. Most zooplankton found in tailvaters are produced in the
upstream reservoir. Some zooplankton may be produced in backwaters and
other quiet-water zones adjacent to the tailvater, but the input from
.. these areas is not significant when compared with that of the reservoir.
Therefore, the species and abundance of zooplankton found in the
55
,.
tailwater are dependent on the species and abundance tn the reservoir
population (Brook and Woodward 1956).
171. The reservoir zooplankton community may vary as a result of
seasonal population cycles . The community is also influenced to a large
degree by the hydraulic residence time of the reservoir. Zooplankton
nwnbers are generally higher in reservoirs with longer hydraulic. resi-
dence time.s·. Both of these factors eventually affect tailvater zoo-
plankton abundance.
172. The amount of zooplankton passed into a tailw~ter depends on
the depth of reservoir release. The zooplankton migrates vertically
within the vater col;.ann in response to changes in light intensity. This
vertical migration may keep the zooplankton away from the level of
discharge during certain periods of the day. Zooplankton abundance
will also be altered in tailwaters belo'lt' selective withdrawal d.ams,
vhere changes in the level of -~thdrawal are made on a seasonal or
daily basis.
173. Zooplankton transported into a tail water f .rom the ·reservoir
provides a more readily available source of . energy a:nd protein than the
·'· detri't~s normally found in. unregulated st~eam's (AnDita.ge 1978). Most
of the zooplankton discharged from hypolimnetic-release reservoirs is
already dead end simply contributes to the stream's load of organic
debris. Moribund zooplankters settle out and decompose, providing a
nutrient-r;i.ch d~tritus in the tailwater area (Armitage and Capper 1976).
Seasonal inconsistencies in the reservoir discharge, hovever, preclude
;o.oplQ.l)kton from being a .reliable source of either nutrient inputs or
food for benthic ~omswnption in the teilva·.'~er (Ward 1975).
174. Le.rger bodied :;,;ooplankters (e.g., copepods and d·aphnid
cladocerans) may be coiiiillon in tailvaters immediately belolt surface-
.release reservoirs, but they rapidly disappear as the water flows
downst.ream. The progressive reduc.tion in densities downstream is
characteristic and has been docmnented by several invest igators
(Chandler 1937; Stober 1963; Ward 1975; Armitage and Capper 1976).
175. The zooplankton decrease vhich occurs between reservoir
outlets and areas downstream is due to a combination of factors,
56
·~ ..
including the abundance of zooplankton discharged , the filterir~
effects of periphytic vegetation in the tailwater, p hysical destruc t ion,
preC::Ltion, and adherence to or ingestion of silt and debr i s . Chandler
( 1937) indicated that zooplankton discharged fr~m a resei"!Foir in July
was ·reduced 99 percent 8 km downstream; whereas, during February, when
population levels were higher, abundance vas reduced only 40 percent.
Algae and mosses in the tailwater essentially act as filters, r emoving
the zooplankton as it flows through the vegetation (Chandler 1937).
Armitage and Capper (1976) noted that 99 percent o f the zc oplankton
discharged had disappeared within the first few kilometres, the
greatest losses occurring in the first 400 m below t he dam . Larger ·-.
organisms become entangled more easily and are eliminated from the
streamflow sooner than smaller organisms. For this reason, greates t
zooplankton reductions in tailwaters may occur when aquat i c vegetation
i s abundant and the tailvat er levels are l o west. When water levels in
the tailwater are high aDd aquatic vegetation is absent, the v e get a ti ve
fi .ltering phenomenon is eliminated, and zooplankton may be more per-
•• ~ •• 0 .
sistent downstream (C~dler 1937). :-;:,';:_'· ~'-"~· ~
176. Zooplankton is also highly susceptible to physical abrasion
and-fragmentation. Some zooplankters a r e ut ilized as prey when f lushed
from the reservoir, benefiting populat i ons of bent hic macroinvert ebrat es
and fish in the tailwater (Ward 1975). Ot her zooplankters eith er ingest
or adhere to sand and s i lt in the turbulent tailwaters and become
heavier, tending to sink and die.
Tailvater Effects on Snecific Invertebrate Taxa
177. The productivity and occurr ence of stream organisms in
tailvaters are determined by physical-chemical stresses imposed upon
the community. These stresses are related to the quantity and quali.ty
of the releases from the re:1ervoir. Species normally present in a
stream may be enhanced or reduced in a tailwater, but t he structure
of the tailwater comnunity is generally much different from that of a
natural stream.
.,
178. Immature life, stages of insects from four orders, including
Diptera, Trichoptera , Ephemeroptera, and Plecoptera, are prevalent ·in
natural streams. Other aquatic insects, mollusks, benthic crustaceans,
oligochaetes, and planktonic invertebrates may also be abundant.
Di 'Dte!"a
179. !n tailwaters, dipterans appear to be the group best adapted
to the al te!"ed conditions of reservoir releases (Ward. 1976c). Dense
communi ties of Simuliidae and Chironomidae often occur in the immediate
tailwater bel0w deep-release reservoirs becau.se major invertebrate pre-
dators are few and fish di~ersities are low (Ward 1976c). They may be
the only invertebrates present because of their ability to adapt to
conditions in most cold tailwaters. Farther downstream in the
tail water elevated water temperatures, predation, and mic·cohabi tat
competition may result in reduced densities of both famil.ies and the
possible disappearance of Simuliidae .
180. Simuliid larvae and pupae prefer cold water and are appar-
ently tolerant of the poor water quality which occasionally occurs in
tail~ters below dee.p-release dams (Hilsenhoff 1971; Goodno 1975). .•-'
· .. They are.· not common below surface-release dSllls or' in ·tailwaters vhere <:
water temperatures may become too high for their survival. The more
diverse .fauna which exists farther downs t ream from these dams addi-
tionally limits t'he establishment of simuliid populations because of
increase.d invertebrate competition and predation .
181. · The various species in the fam:i,ly Chironomi.dae are .adapte~
to a •'ide range of environmental conditions, making them ideal
tailwater inhabitants. Some prefer cold water, while others prefer
warm water. Other species have more generalized requirements and may
be found in a variety of conditions. The seasonally altered tempera-
tures found in tailwaters below deep-release dams (winter warm, summ.er
cool, and delayed maximtml and minimum temperatures) may a l low some
species o f chi·ronomid larvae to survive during periods of the year when ·
they would not be found in natural streams. However, these same
alterations may modify emergence patterns, which are controlled by
water temperature and light intensity (Oliver 1971). Adults in t hese
58
-----------------------------------------~
·. ..
-· .. . '
.....
.. ·; :.·· .. · .
•
. '
..
.'
instances me,y undergo premature emergence ~esulting in disorientation
and reduced survival.
Tric.hoptera
182. Most. species of Trichoptera found in tailwaters are net
spinners or filter feeders. Their abundance is directly relat ed to the
availability of seston discharged fl'om the ,reservoir which, in turn, is
dependent. on the location of reservoir outflow (Rhame and Stewart 1976;
Ward l976a). Deep-release reservoirs provide an extremely unreliable
food source because of the lack of seston during periods of stratifica-
tion. Unstratified and surface-release reservoirs may, in contrast,
provide a rich food source, including plankton and other suspended
organic matter.
183. The success of a certain species may depend on the si~e of ··
the food particles that are available. Individual species crop parti.-
cles of specific sizes, depending on the mesh size of their gathering
apparatus and their location in the streambed (Wallace e~ al. 1977).
184. Variations in flow alsc affect trichopteran survival. Ade-
quate current v~locities are necessary to supply rood and oxygen to
stat.ionary larvae and influence the design and construction ot
food-gath~ing nets (Haddock 1977; Wallace et al. 1977). Sufficient
·· flow is required to keep :food-gathering nets extended!, but higher flows
will result in their destruction (Haddock 1977). Large flow varbtions
below s0111e dams may inhibit the survival and feeding success o 'f .some
trichopterans, since food-gathering nets are swept away at high tlo~s
and collapse at low flows. .. .......... ,
•u '•"
185. Larvae of some species of Trichoptera a:re found in. -
quiet-water areas of natural streams. They are unable to vi thsta.nd
swift water and are not dependent on net-gathering mechanisms for
their food supply. Quiet-water areas are uncommon below most reser-
voirs and if pre.sent they a:re subject to destructive periodic flow
increases. As a result, most trichopterans found in tailvate'rs are
adapted to living in svitt water.
, .
59
·'·· .
. ~
....
..
Eoheme::-optera
186. Ephemeropte:::-~ {mayflie.s) typicaJ.ly inhabit small streams vi tb
large-rubble substrates. The number of species present depends pri-
marily on the habitat diversity, since each species exhib'its a high
degree of habitat selectivity. Generally, the presence of more diverse
habitats is reflected by an increase in the number of species (Macan
1957) •.
187. Ephemeropterans do not usually occur in ta.ilwaters be.cause
the stable thermal regime found here does not provide ~he temperature
stimulus required for life-stage development. They are additionally
affected by the reduced habitat. diversity and the. abse~~e of. ai:i aae.:..
quate food supply (detritus). Downstream, where the effects. of reser-
voir releases subside, mayflies gradually become more prevalent as the
tailwater becomes more "stream-like" (Lehmkuhl 1972).
188. Ephemeropterans are rarely found in streams where velocities
are below 15 em/sec or above 91 em/sec (Delisle and Eliason 1961). Fev
species are able to survive in areas subject to extreme flow .reduction's
, ., .(MacPhee and Brusven 1973; Ward 1976a) •. Mayfly species equipped vito .... ., ...
hold-fa.st organs are able to exis·t in tailwaters vi th :noderately high
current velocities (Ward 1976a).
189. Most e~hemeropterans do not readily colonize areas in a
constant •state of vater-level ·fluctuation. since they cannot tolerate
both lov and high flov extremes. One genus (Paraleptophlebia), however,
bas been found abundantly in t .ailvat.ers exhibiting t 'hese types of
fluctuations (Trotzky and Gregory 1974).
Pleco-otera
190. Plecopterans are usually not found in tailvaters because ·
the lo•ss of habitat heterogeneity, changes in flov regime, and re-
latively stable temperatures make conditions unacceptable for their
grovth and development. Downstream their abundance gene.rally increases
as the influence of the reservoir discharge declines (Ward 1976a).
Several species of plecopterans (e.g., chloroperlids) are not affected
by rapidly fluctuating flows, and may become abundant in tailvaters
60
. .
where other environmental condi tions are suitable {Ward anq Stanford
1979).
191. Plecopterans are common predators on trichopteran eggs,
cbironomid larvae, and simuliid larvae in natural streams (V,aught and
Stewart 1974). The absence o~ these predatory species. contributes to
the increased abundance of Simuliidae and Chironomidae in most cold
tailvaters.
Misce~laneous
192. Amphipods ., oligochaetes, i sopc.ds, mollusks, and turbellarians
a:re often abundant. in tail waters. One fE•ctor common to these groups
that may be significant to their abundanee in tailvaters is the lack of
an aerial adult stage in their life cyclt~s. Becau.se they do not have
an aerial adult stage, they are not subj·~ct to the problem of :pTemature
emergence that often occurs among aquati·~ insects in thermally e.ltered
tailvaters (Ward and Stanford 1979).
193. Ward and Stanford (1979) indi '!ated that amphipods arE often
abundant in tailvaters that have reduced .summer temperatures anc . stable
. .
·flow regimes. High nutrient inputs and '!"educed flood flovs alsc• favor
amphi'pods because st-reambed siltation an•i increased macrophytic growth
vhi.ch occurs in the:;e situations are hig:lly beneficial to thei.r develop-
ment (Hilsenhoff 1971).
194. Oligochaetes may be present b•!lov deep-release· reserYoirs in
pools avay from the strongest currents. T'he cool, nutrient-rich water
and lack of destructive spates favor estt~blishment of dense populations
in these areas (McGary and Harp 1973; Armitage 1976).
195. Isopods may be the· dominant organism in the riffle areas of
cold tailwaters (McGary and Harp 1973). They are also less a!f~!Cted by
minor vater-level fluctuations than other invertebrates because· they
can migrate out of areas that are periodi ·::ally exposed.
196. The distribution of mollusks in natural st-reams is d~!ter
mined primarily by substrate patterns and type~. The chemical nnd
physical alterations that occur in tailwater environments have both
enhanced and disrupted mollusk populat.ions.
61
197. .Enriched growths of attached algae and increased organic
sediment were found to encourage the establishment of pulmona:te snails
(Physa} during the absence of scouring releases or during extended.
periods of reduced flows (Williams and Winget 1979). However. Harman
(1972} found that chemical and biological alterations of tbe tailwater
environment negatively affected t~e mollusk population and reduced
sp~cies diversity. The number of mussel species was also reduced in
the Tennessee River. Alterations to and loss of riverine habitat after
extensive reservoir construction reduced the number of species from 100
to approximately 50 (Isom 1971). Formerly abundant species were re-
¢uced or eliminated and natural replacement was limited. The change in
fish species that also occurred as a result of reservoir construetion
further reduced mollusk populations through the ·obstruction of f'i:sh-host
associations that are a necessary part of the molluskan life cycle
( Isom 1971) .
198. Turbellarians appear to be a minor member of the tailwater
invertebrate community and are not widely studied. Based on the few
studies tha:t .have been conductedt turbellarians apparently increased
:in.tailwaters with stable flow regimes and cool summer tempera~ures ·
and declined in tailwaters with fluctuating flows (Ward and Stanford
1979).
199. Crayfish are common in some tailw&ters; however, no mention
of this group was made in the li ter.ature except as .food for some fish
s .pecies.
62
• ':.., .. 'l.-;
• • 'j • ••.• ··.· ...
.. ·.·
PART VII: FISHES Ili TAIL'WATERS
200. In this section, fishes that commonly occur in tailwaters
are discussed. The presentation i.s by family, followed by individual
s~cies or groups. Fish species which occur in tailvaters but 'are of
only mi.nor importance because few are generally captured or they are
little mentioned in tailvater literature are not discussed. These
include species from the folloviog families.: Petromyzontidae (lam-
preys); Acipenseridae (sturgeons); Lepisosteidae (gars); Anguillidae
(eels); Hiodontidae (mooneyes); Aphredoderidae (pirate perches);
Cyprinodontidae (killifishes); and Atherini.dae ( silve·rsides).
201. A brief description. of enviromnental conditions nece.ssary
for the successful completion of the various life bistory phases of
eac.h species or group is presented under the following topics:
habitat, reproduction, .food, and age and grovth. This is followed by
a synthesis of tailvater literature pertaining to a particular species
o~ group of fish. Emphasis is placed on how the species responds to ..
· ·· · environmental conditions found in tailvaters· •. The depth of discU.ssi'on ..• :;-:·=~:.~. ~ ..
varies by species and is dependent on the amount Of literature avail-' :
able. Source material for the descri.ption of f'ish life history require-
ments vas obtained fro111 Carlander (1969, 1977), Scott and Crossman
(1973), Pflieger (1975}, and others.
202. The common and scientific names of fishes mentioned in this
-report are listed in Appendix C . Fishes from North American tailvaters
a.re· included in Part I and nomenclature follows that or Bail~ et al.
(1970). Fishes from European tailvaters are included in Part II.
Life history information for the most common fi.sh groups discussed in
this report is' given in Appendix D.
.....
Polyodontid&e (PaC.dlefishes) .. · • .....
203. The paddlefish is one of the largest freshwater fish in
North America. It is found only in the Mis-sissippi, Missouri, and
Ohio rivers ,and their larger tributaries. Numbers of paddlefish have
•• 1
declined greatly since the advent of the twentieth century. Major
causes are believed to be dams,. over fishing, and pollution. Fish con-
centrate below dams vhere they are especially vulnerable to fishing.
Dams built to create reservoirs or for other pur·poses have inundated
many former s ,pavning grounds or have prevented fish from reaching
upstream spawning areas. The dec~ine of paddlefish stocks in past
years followed the increased rele~se of domestic and indu~trial pollu-
tion into the waterways. Paddlefish populations have increased in some
areas where pollution abatement has been ef'fective (Eddy and Underbill
1974).
Paddlefish
204. Habitat. The paddlefi sh is primarily found in the. open
vater of sluggish pools and backwaters of large rivers where it svims
about continuously near the surface or in shallow water. For spawning,
it requires access to a large, free-flowing river vitb gravel bars
vhi.ch are inundated during spring floods.
205. Orig.inally the large. free-flowing rivers of the M:tssissippi
.;~-..
Valley provided ideal habitat for paddlefish. Nov some of the largest
populations are found in man-made impoundments where tributary riTers
.meet the fish's exacting spawning requirements. These conditions are
met in some reservoirs in the states of Alabama, Arkansas, Kentucky,
Missouri, OklabCIIIB., and Tennessee, and in several mainstream M:is.souri
River reservoirs in North and. South Dakota and Montana.
· ·206:· Reproduction. The reproductive habtts of paddlefish ·were
descrioed by Purkett (1961), whose studies were conducted on tbe Osage
River in Missouri . Spawning takes place in midstream, over sul:merged
gravel-bars vhen the river is high and muddy in early spring at temper-
atures of about 15.5°C. Meyer and Stevenson (1962) reported that
female paddlefisb in Arkansas do not mature until they are over 11.34
kg in weight and that they may not spawn every year. The adbesi ve
eggs stick to the first object they touch, normally stones on the
streambottom. Eggs hatch in 9 to 12 days vben water temperat.ures are
about 16°C (Purkett 1963; Needham .1965). Afier hatching, the. fry svim
upward vigorously, then settle toward the bottcn. Frequent repetition
64
~ ....
of this activity by the fry is significant in that it permits the
strong currents to swee·p the fry downstream out of the shallows and
into deep pools before the gravel bars are exposed by receding vater
levels.
207. Food. Paddlefish feed primarily on ~ooplankton and insect
.larvae filtered from the water. They svim slowLy with their mouths
open through areas whel"'e food is concentrated. Water passed through is
filtered by the long, closely set gill rakers. The function of the
paddle-shaped snout in relation to feeding is not knovn for certain,
but its elaborate system or sense organs may enable it to function
primarily as a device for locating concentrations of food organisms.
208. Age and growth . Paddle.fish grow rapidly. According to
.. Pflieger (1975), yoUng nearly 150 ·mm :'tong have been collected from
overflow pools of the Missouri River in early July. Two specimens
kept in a fertilized pond reached a length of about 0.9 m and a veight
of 2. 7 kg when they vere 17 months old. Paddlef'i sh in Lake of the
OzP..rks, Missouri, attain a length of 250 to 350 mm in their .first year
~:• • .,., "• ·.;, • • :::0 "" " •· ''•. .....( ·~~···· •1 I ~1d about 530 mm in their second year. Seventeen-year-old fish average
ne~ly 1. 5 m in length ana 16.8 kg in we.ight. The ·largest paddiefish
are usually females. The species is also long-lived; many individuals
live more than 20 years.
Paddlefish in tailvaters
209. Large concentrations of paddlefish are found in some
tailvaters es,pecially during winter and spring. Most studies on
· · paddlefish in tailwaters are concerned vith spawning and reproduction.' ········
Paddlefish reproduction, prevented primarily by the blockage ~f
lloPStream migration by dams, has also been affected by the altered flow
regimes found in tail waters. Main-stem hydropov--er facilities on the
Missouri River have not only reduced the amount of natural spavning -
are.a available but have. also rendered most of the remaining river areas
unusable. Large diel water fluctuations mask or delay the normal
spring r .ise in water flows and temperatures.
210. Young-of-the-year fish have been reported in only one
tailvater of the Missouri River reservoir system (Friberg 1974).
Juvenile·s found 1:-. Levis and Clark Lake were produced in the 65-km
section of the Mi s souri River above the reservoir, while those in t 'he
tailwater either passed through Gavins Point Dam or were produced in
the 97-lan section of natural river downstream from the dam (Walburg
1971; Friberg 1974). Recruitment from the reservoir above is believed
to be the primary source for paddlefish found below Lake of the Ozark's
hydropover dam on the Osage River in Missl')uri (Hanson 1977).
211. ·The effects of navigation or flood control dams on paddlefish
reproduction are not as wel.l defined. Successful spawning on. eroded
ving dikes below Lock and Dam Number 12 on the Missl~sippi River in·
Iowa has been regularly observed (Gengerke 1978). Eroded ving dikes
effectively simulate natural gravel bars. The control of spring .
floodwaters below a Kentucky flood control reservoir appears. to inhibit
downstream spawning activity (Branson 1977).
212. An alteration of the behavioral characteristics of paddle fish
caused by impoundments is evidenced by their concentration in the
svift-floving waters immediately below many dams (Friberg 1972; Boehmer
1973; Gengerke 1978f~ Concentration of these :fish into a relatively
confined area increases their vu.lnerability to both commercial and
sport ~ishing. Friberg (1974) reported high catch rates of paddleti.sh
in tailvaters for three to four years following dam.closure, folloved
by declining catches due to reduced numbers. These concentr·ations dur-
ing the reproductive season may be explained by the blockage of upstream
migration. During other seasons these concentrations are mo.st likely
due to the increased availability of food i .n the. reservoir discharge·.
213. In tailwaters, zooplankton is most abundant in the reservoir
discharge; :its abundance decreases rapidly downstream. The large
quantity of food available would tend to attract feeding paddlefish from
slow-flowing areas into the faster floving discharge, where they would
normally not be found.
214. Except for the immediate discharge, there is general.ly less
zooplankton available in the tailwater than in the reservoir. This
relative scarcity of food is reflected in the reduced growth rates of
tailwater paddlefish. Growth studies by Friberg (1974) indicated that
66
~ .. _ ..
·,
. .... . .
. ·· ...
paddlefish apparently raised in a ·reservoir suffered a·marked reduction
in grovth following passage through the d.am into the tailvaters.
Clupeidae (Herrings)
215. The herring family is composed, of species which are ma~nly
marine or anadromous. Several species live in fresh water and ~re
occasionally' found in tailwaters. They are skipjack herring, gizzard
shad, and threadi"in shad . None are used for human food, but the skip-
jack is sometimes sought by sport. fishermen because it fights specta:-
ularly when hooked. Gizzard shad, particularly young of the year, are
important forage for other fishes•. Thread.fin shad are important forage
at all ages because t ·heir maximum length rarely exceeds 180 mm. The
skipjack is not discussed. further here because it is little ntentioned
. in tailwater litera.ture, ex~ept. for an occasional occurrence in fish
species lists.
Shad
216. Habitat. The gizzard shad in genera.l..l.y distributed o.ver the . ' eastern halt of t.he United States where it .is most abund8Jlt in reser-
voirs and large rivers. -It inhabits'quiet-water habitats ~n lakes,
ponds,. reservoirs, and backwaters of streams where· fertility ~d pro-
ductivity are high. Shad. usually avoid high-gradient streams and those
which lack large, permanent pools. Shad congregate into loose aggrega-
tions, and large numbers are often observed near the water surface •
During tall, winter, and spring, large numbers may be found in
tailwaters.-
.217. The thread..fi·n shad, whose babi.tat is similar to that of the
gizzard shad, is generally confined to the southeastern states where it
has been stoc·ked extensively in reservoirs for forage. It has also been
stocked in reservoirs of' the Southwest. It is sensitive to low tempera-
tures, a .nd extensive die-oft's ha,ve been reported at temperatures below
7.2°C (Pflieger 1975). Because of overwinter die-off, annuaA stockings
of a...dults are necessary to maintain populations in many reservoirs.
Large .rv.Jmbers of this ·species may also occur in tailwaters during fall
and winter.
67
'·
L
218. Reoroauction. Gizzard shad are very prolific and generally
spawn during April, May, and June at temperatures between 17 and 23°C
in shallow areas of protected bays and inlete. The scat:tered eggs sink
to the bottom where they adhere to the first object they contact. Eggs
hatch in about_4 days. and the young begin feeding when 5 days old.
Young at-tain typical adult form when abo'.lt 32 mm ll"lng. ·
219. Thread!'in shad begin spawning i n the spring vben the water
temperature reaches 21.1°C and may continue throughout much of the
summer.· Threadfin spawn in schools near shore. The -adhesive eggs
stick to any submerged object and 'hateli in about 3 days. Young begin
'feeding when 3 days old. Individuals hatched early in the year com-
monly mature ana spawn late i n their first summer of life .
220. Food~ The gizzard shad is almost 'entirely herbivorous,
feeding heavily on microscopic plants, phytoplankton, and algae. The
species is essentially a filter feeder, removing particulate matter
from the water by passing it through its closely set gill rakers.
221. Threadfin shad are also filter feeders. Their diet consists
ot microscopic plants and animals found in the water ·column .
. 222. · Age. and growth. Gizz ard shad average• about 127 mm long at
the end of ·their firs-t summer, 185 mm at age I, 257 mm at age II, and
302 mm· at age III (Car lander 1969) • The average' life span is 4 to 6
years but s.om.e live 10 or more years. Maturity is reached in the
second or third year. Adults are commonly 230 to 360 mm long and veigh
about 0.45 kg. Maximum. length and weight is about 520 mm and 1.6 kg.
223. Adult threadfin shad are usually 102 to 127 mm long, and .
. few live more than 2 or 3 years. In Bull Shoals Reservoir, Arkansas,
threadfin shad average 53 mm in length at the end of the first growing
season and 124 (males) and 135 (females) mm at the end of three gro'l.'ing
seasons (Bryant and Houser 1969).
Shad in tailwaters
224. Shad are important forage species in tail waters. Both
gizzard shad a .nd thread fin shad are eaten by striped bass, trout,
wu.lleyes, sauge.rs, and other species (Parsons 1957; Pfitzer 1962;
Walburg et al. 1971; Deppert 1978; Combs 1979). Threadfin shad have
68
. ~ ., ;,
.. .. .......
.been stocked in sane reservoirs specifically to provide food in the
tai.lwaters for piscivorous fish (Parsons 1957).
225. The number of' gizzard and threadfin shad is generally higher
in tailwaters than in natural streams due to their mo'V'ement from re.ser-
voirs either over or through dams (Clark 1942; Parsons 1957; Louder
1958; Pfitzer 1962; J. P. Garter 1968a, 1968b, 1969; 'Walburg 1971).
Occurrenc:e of shad in tailwate.rs appears to be 1:10re related to season
than magnitude of outnow from the reservoirs (Clark 1942; Parsons 1957;
Louder 1958). ·The presence of impoundments has also increased shad
distribution. In Oklahoma, shad became established in a tailwater
where they did not appear in the natural s t ream prior to illlpoundment
(Cross 1950).
226. Dams also affect anadromous members of the clupeid family by
acting as barriers to upstream spawning migration ( 'W. R. Carter 1968;
Foye et al. 1969). Large numbers of American shad concentrated below
a ~am in Maryland during spring. Fish kills sometimes occurred when
the turbines were shut down during normal peaking o·perations and dis-
solved. oxygen in the tailwaters was reduced to lethal levels ('W. R.
Carter 1968). ·Alteration of operating procedures to provide mainte--..
nance flows of 141..6 m3 /s.ec through each of two turbines has been
required to avoid further low-oxygen fish kills. Maintenance of
minimum flows has been credited with allowing the survival of American
shad in the Ru ·ssian River in California (Anderson 1972).
Sal.monidae (Trou.ts)
227. The trouts are coldwater fish which were originally found
in the Arctic and North Temperate regions. Over the years they have
been introduced into suitable waters throughout the world. Many
coldwater tailwaters in the United States have been stocked with
hatchery trout on a put-and-take basis. Stocking is done at regular
intervals throughout the fishing season to maintain a satisfactory
sport fishery. Catchable-size trout. (150-200 mm long) are usually
...
stocked because smaller fish oft en have poor su.""Vival to the creel
(Vestal 1954).
228. The rainbow trout is the, most common sal.monid stocked below
dams bec,ause it is less costly to 'raise and easier to catch. Other
salmonids planted in tail waters are brown trout, brook trout, a.nd coho
salmon. Rainbow trout are usually stocked in the coldva.ter tailwaters
belov rese:-voirs built on varmvater streams. Rainbow trout or other
trouts may be st.ocked or may occur naturally in coldwater tailwaters
below reservoirs built on coldwater streams. Discussion here is limited
to the rainbow trout because it is the most common trout in tailvaters.
Rainbow trout .
·229. Habitat. The rainbow trout is native to the streams of the
Pacific coast where many varieties or subspecies have developed. The
seagoing form is known as the steelhead trout and is believed to be
identical to the strictly fre,shva.ter rainbow trout. Because of the
ease wit-h which eggs of the rainbow trout can be transported, different
strains have been distributed throughout, the world,.
230. This species lives in a variety CJf habitats, inc~uding
streams, lakes, and reservoirs. The rainbow trout tolerates somewhat,
higher temperatures than·other trouts but does best in, waters that
remain more or less continuously below 2l.l°C. According t9 McAfee
(1966), the upper temperature limit for the species varies fr.om about
23.9 to 29.4°C, depending on the oxygen content of the water, size of
fish, and deg:-ee of acclimation. Cold waters discharged from the lover
levels of so.me reservoi.:-s provide adequate tailvater babi tat for this
species, provided year-round oxygen levels remain above 5 mg/1.
231. Rainbow trout thrive in small to moderately large streams
and shallow rivers, with modere,te flow and gravel bottoms of the
pool-riffle type. They generally prefer riffles and fast-water areas.
Depth criteria have not been defined for trout in general; however,
the depth of pools and amount of cover appear to be very important in
terms of' fish size. Gunderson (1968) found that stream sections
lacking.deep pools and adequate cover contained only fingerling trout,
while stream sections with deep pools separated by riffle are:as
70
'·
···•· ....... ... ............
. '
contained much .larger trout. Trout. req~re adequate stream depths for
normal intrastream movement. Riffles are extensively used for feeding
areas and tor movement between pools (Giger 1973). Minimum ~epth
requirements over riffle areas vary with the size of the stream and the
trout inbabi ting it; hovever, minimum water depth over ri.ffles should
probably not be leu than 0.18 m. Giger (1973) listed the optimal pool
depth for cutthroat trout as 0.4 to 1.1 m, depending on age and size.
Hooper (1973) stated that for trout in general, areas with velocities
betveen 9.1 and 31 em/sec are preferred for resting.
232. Reproduction. Rainbow trout spawn between early winter and
late spring, depending on the genetic st·rain and stream conditions.
The eggs are deposited in a shallow depression dug by the female on a
· clean gravel riffle. Females deposit between 200 and 9000 eggs in the
nest (redd), depending on fish size. After all eggs are laid and
fertilized, they are covered with gravel. The incubation period varies
with temperature, averaging about 80 days at 4.4°C and 19 days at
Young remain near the hatching site for a while, tending to
' . -school at first and then become solitary and more widely. distributed._
233. According to Hooper (1973), the optimUm spawning temperature
for spring-spawning rainbow trout is 11.1°C, but ranges from 7.2 to
13-~3°C. _Preferred g;avel si~e is 0.6 to 3.8 em in diameter, and pre-
fe~rred velocities for spa~ing a~~-between 42 .6 'and 82.0 em/sec.
234. Food. Rainbov trout eat a wide variety of foods but depend
primarily on drifting insects. A compilation of' the findings of many . -. .
studies indicat.es that immature and adult aquatic insects . (principally
.. caddisflies, mayflies, and dipterans), zooplankton, terrestrial
·insects, and fish are usually the most significant foods, though their
relative importance varies greatly between waters, seasons, and size
of fish. Large trout include more fish in t -heir diet. Oligochae.tes,
mollusks, fish eggs, a.mphipods, and algae are foods eaten less ex-
tensively, but they may be important locally. For example, in upper
Lake Ta:neycomo, below Table Rock Reservoir in Missouri, amphi.pod
crustaceans make up almost 90 percent of the trout diet (Pflieger
1975).
71
·•''-
L
I
235. Age and growth. Fev rainbov trout live beyond 6 years, and
life expectancy for most is 3 or 4 years. Longevity is influenced by
. marcy-.interrelated factors. Poor food conditions may result ·in poor
survival after first spawning. Heavy angling pressure may crop most ...
fish before they are 4 years old. This is especial1y true for fish
stocked in ta.ilvaters, where most may be captured during the same year.
236. Maximum size of rainbow trout varie·s greatly among different
environments. In small streams adults rarely reach 205 mm; whereas in
large lakes individuals occasionally exceed 13.6 kg. Maximum size
depends primarily on growth befo'!'e attainment of sexual maturity, which
in turn is dependent on quantity and quality of available food . Most
growth occurs during the first tvo graving seasons. Growt.h is fair
for fish on a plankton diet, and is best where forage fish are abun-
dant. Growth usually dec.lines after maturity is reached; this decline.
is especially evident in waters where large forage organisms are
lacking.
237. The rate of growth varies seasonally and at different ages,
·depending on water temperature, strain of trout, feeding conditions,
·age at maturity, and other factors. For example, in waters vith re-
latively high temperatures throughout the year, such as the tailvaters
of some reservoirs in the southeastern United States, growt.h is· fairly
constant in all months·; whereas, in vaters vi th seasonal temperature
changes, growth is slaver or ceases in the 'Winter.
· 238. Hatc.hery-reared trout reach a length of 205 to 254 DDD vhen
about one year old, at which time they are considered large enough to
s~ock. In Lake Taneycomo, Missouri, where conditions for rapid growth
are favorable, stocked rainbow trout grov about 19 DDD per month
(Pflieger 1975). Naturally reared rainbow trout in Minnesota reach
125 DDD the first year, 230 mm the second, and 521 DDD the fifth year
(Eddy and Underhill 1974).
239. The weight of rainbow trout varies greatly at lengths over
380 mm because of differences in feeding conditions and s.tage of
maturity. Fish are heaviest where food is abundant, particularly in
72
• ... • ..
":.'.
.•·
... · , ..
lakes. According to McAfee (1966), weight of fish in average condition
by 127 -mm fork lengt-h groups is as follows :
Len~h 1 mm Mean veisht 2 kg
127 0.028
254 0.227
381 0.568
508 1.589
635 3.178
762 4.767
Most fish spavn by age III; .males one year earlier than femal.es. Size
at maturity is extremely variable but usually ranges between 254 and
381 .mm. In California, mature rainbow trout typically veigh less than
0.45 kg (McAfee 1966).
Rainbow trout in tailwaters
240. Habitat . Trout are found in most tailwaters throughout the ·. ...
United States vbere s ummer water tempe·ratures normally do not exceed · :.
-.. . . ~· .
21.1 °C. They may occur naturally below dams built on coldwater streams
or the.y maY be stocked in tailvateTs below dams on warm:water streams
'!lbere hypolimnetic releases maintain coldvater ·conditions throughout
the year . Tail waters below most deep-release re·servoirs ha.ve lov
turbidity, cold temperature, and s tabilized seasonal flov, thus pro-
viding satisfactory trout habi ta'.:. These t a ilvaters often provide
coldwater habitat on streams in areas such as Texas and Arkansas,
where trout could not live before dams vere constructed .
241. The quantity and quality of col.dvater habitat in a tailvate!"
suitable for trout are a function of reservoir design and operation,
as vell as tailvater physical characteristics. ResE'rvoi r features
that determine habitat suitability include rese!"-.roir stratification ,
reservoir storage capacity, reservoir storage and release patterns,
and intake locati.on. Tailvater f eatures that influence habitat suit-
ability are water tempera.ture, stream channel configuration, st!"eam
substrate, stream cover, water depth, water velocity, water quality,
73
•·.
turbidity, and tributary inflow. These factors act in combination with
stocking to determine trout abundance and distributi·on.
242. NUI:lerous fish species are ·found in association. with rainbow
trout in many tailwaters. Most compete with the trout for food and
habitat. Game fish inhabiting these waters include largemouth and
smal.lmouth bass, bl.uegills, longear sunfish, and catfish. Brown and
brook trout. may alsc-occur in the same location. Cyprinids, suckers,
sculpins, &nd sticklebacks are major nongame competitors.
243. Low flow, sometimes aggravated by elevated water temperature,
is a coi!IDon factor limiting trout distribution and abundance in many
tail waters. Low flows can decrease cover, increase· overwintering
mortality, allow sediment accumulation, and cause stl"a.nding. Reduction
of flow in a Tennessee tailwater limited habitat to a long shallow pool
with bedrock substrate and 11 ttle c.over (Parson! 1957). Kraft ( 1972)
found a 62 percent decrease in brown trout habitat when flow was
reduced. 90 percent in another site. Weber (1959) found that when annual
flow below a reservoir was reduced to 11 percent of the long-term
average, trout habitat was reduced 82 percent.· Flows that reduce water
.~.depth over riffles to 7.6 em or less make .these areu unusable to' large
trout (Corning 1970). Decreased f l ows and thus decreased water velocity
favor small trout and rough fish over large trout. Lov flows a l so
cause a redistribution of trout to less suitable habitat, incre.asing
competition with other fish. Corning (1970) also foU:Jld that re~uced
flows concentrate. fish in the remaining habi tat ·.and intensify predation • . -. . . .. ·~ .
: . 244. In the vestern United States, irrigation-storage reservoirs
colleet surface runoff during winter and spring to be used during
summe r irrigation. Holding runoff decreases stream flows during the
winter and spring vhich can i ncrease trout mortality. Adequate reser-
voir discharge is critical during winter to sustai n a tailwater· trout
population . The survival of 3-year and older trout was di'rectly re-
lated to the magnitude of flow from a reservoir during the winterr
storage period (Nelson 1977). Vincent (1969) stated that dewatering
below a da:n in Montana resulted in excessive mortality of young (age I)
trout . Studies in Wyoming shoved that seasonal minimum •flo.,.s were
. :·· ..
. . ···
··I .
essential for trout survival. Winter flows of 14.2 m3 /sec wer~ recom-
mended to maintain adequate cover for overwintering trout. Spring and
summer flows of 22.7 m3/sec were recamnended to select against rough
fish and for large trout, and flows of 45.3 m3 /sec were recommended
periodically to flush silt from the tailvater. A 30-day survival flow
of 8.5 m 3 /s~c was recommended for times of extreme water shortage
(Banks et nl. 1974).
245. Low flows in tailwaters allow sediment accumulat.ion in holes
and over· gravel sub~trate, thus limiting the quantity of trout. habitat.
Sediment input into tailva.ter·s is usually from tributary inflow or the
erosion of alluvial banks vi thin the tailvater. Reduced spring flows
below a dam in Montana increased sediment accumulation by tributary .
'inflow. Timed spring discharges from the dam are used to wash sediment
downstream (May and Huston 1979). Seasonal flood .flows over· the spill~
way removed. sediment from a tailva.ter in Alaska (Schmidt and Robards
1976). Sediment accumulations behind a dam in California wer·e reduced . .
by periodic flushing into the tailwater, which caused destruction of
trout .habitat for 1.6 t o 3.2 km downstream (Anderson 1972). ~.·
246. ·High flows and flow fluctuations in ·tailvaters can be
limiting faetors for certain size classes of trout. Banks et al. ( 1974)
found that water velocity increased sharply with increased dam dis-
charge. Trou.t . 30 em long or longer were favored over smaller trout and
rough fish because of lack of resting cover and high water velocities .
High water velocities and sparse cover results in low standing crop
(26.1 and 4·2.6 kg/ba) and harvest (7.7 and 8.6 kg/ba) of trout .. The
trout th.a.t. remain are usually large and weigh "Jetween 0. 7 and 5.5 kg
(Mullan et al . 1976). •.
247. Rapid flow fluctuation below both hydropower and diversion
dams has caused stranding of both trout and salmon (Anderson 1972;
Kroger 1973; Fowler 1978). Kroger (1973) suggested that decreasing
flows at a ma.ximum rate of 2.8 m3 /sec/day would reduce stranding . of
f1sh below· a dam in Wyoming. However, the most serious effec.t of flow
fluctuations appears to be reduced trout reproduction, rather than a
75
...
~ .....
I ;
I
dire.ct increase in adult fish mortality .(Parsons 1957; Baker 1959;
Axon 1975).
248. The cold temperature of tailwaters below 'hypolimnetic re-
lease dams built on warmvater streams helps trout to compete effectively
with or replace native fish species. Vanicek et al. (1970) found native
fish replaced by rainbow trout in the 42 km of river below a dam in Utah
and Colorado. Lover water temperatures below a d.am in Texas caused
partial replacement of 20 native species by stocked rainbow trout
(Butler 1973).
249. Dams with hypolimnetic releases built on coldwater streams
have altered the'habitat by lowering water temperature~ and stabilizing
fiovs. Belo·v a Colorado dam, reduced water temperature caused a re-
distribution of trout species, with brook trout moving into the colder
water near the dam (5.0-8.3°C) and brown and rainbow trout moving into
the warmer areas d.ovnstream. After completion of two Colorado dams,
summer water temperatures in the tailwater were reduced by 3.2 to
5:0°C. The temperature reduction is believed responsible for trout
appear_ing in areas where they were pr·eviously :r;are or absent (Mullan
et al. 1976). P~naz et al. ( 1968) stated that . the Vir tail water on
the Svratka River, Czechoslovakia, bad. reduce.d water temperatures and
stabilized flows d.uring the summer, and these conditions favored brown
tro·ut over case, a warmwater species. .Nase. we·.re reduced from 63.4 to
12.7 percent o·f' the tailvater fish harvest and brovn. trout increased
to'76.8 percent.
250. In addition to reduced maximum temperatures, the seasonal
rate of temperature increase is slowed in many cold tallwaters. In a
Montana te.ilwate.r, tl;le normal spring water temperature of 12. 8°C is
achieved 6 to 8 weeks later than it vas before the dam was built. This
change delays the spawning of suckers and. gives trout a competitive
advantage in the tailvater (May and Huston 1979).
251. Reduced stream flows (usually less 'than 10 percent average
daily flow) during period,s of warm air t .emperat.ure can c.ause vater
temperatures to exceed lethal levels for trout. This situation. often
occurs in natural streams, in tailv-aters below deepwater release
76
-: I
reservoirs on formerly warmvater streams, and belov hydropower dams
that discharge only during periods of high e'lectrical demand. Dendy
and Stroud (1949), Parsons (1958), Baker (1959), Kent (1963), Geen
(1974), Axon (1975), Aggus et al. (1979), and others have stated that
high water temperatures may 11mi t trout populat.ions in tail waters.
Many reservoirs have incorporated minimum water releases in their
opera~ting schedule to maintain suitable flows and water temperatures
in tailwaters. The U. S. Bureau of Sport Fisheries and Wildlife (1969)
rec<Dmended a minimum t'lo\1 of 7.1 to 11.3 m3 /sec to maintain the trout
fishery in a Wyoming tailwater. Suitable trout water temperatures are
maintained for 9.7 km below Canyon Dam, Texas, by cold hypolimnetic
discharge (Butler 1973).
252. Extremely cold water temperatures were associated with the
loss of a trout fishery in several tai.lwaters. A New Mexico tailwater
·experienced an 8-month average water temperature decline from 10°C in ·
1968 to 5°C in 1971. This temperature change was associated with a
decrease in trout harvest from 78,656 fish in 1968 to 10,642 in 1971
( Mull~f et ·-al. 1976). In a similar situation, an average tr~ut harvest.
of 109.5 kglha was recorded when annual water temperatures ranged from
3.1 to 12.00C; however, when the average annual temperature range
decreased to between 4. 2 and 9. 2°C, the trout harvest dec.reased to
only 6. 2 kg/ha (Mullan et al. 1976) .
253. Low dissolved oxygen concentrations and gas supersaturation
resulting in nitrogen embolism can cause mortal.ity or trout in other-
vise suitable tailvater habitat. Low dissol7ed oxygen is a problem
·often encountered in the southeastern United States in tailvaters of
deep-release dams built on varmwater streams. This oxygen deficiency
occurs when a reservoir thermally stratifies and decomposition of
organic matter within the hypolimnion consumes available oxygen.
"Nitrogen embolism may occur when fish inhabit tailwaters that are super-
saturated with atmospheric gases and the body fluids of the fish also
become supersaturated.
254. Trout generally prefer water with 5 mg/1 or more dissolved
oxygen. The species may not survive when hypolimnetic release water ·
77
conta_ins little or no dissolved oxygen. The penstock design at some
dams does not allow for aeration of hypolimnetic water before release
' into the tailwaters. Low dissolved oxygen vas. found to limit the fauna
in some tailwaters (Hill 1978). A dissolved oxygen concentration of . -
0.8 mg/1 presumably caused the death of about 100 rainbow trout in an
Oklahoma tailwater (Deppert 1978). However, a dissolved oxygen concen-
trat.ion of 2 mg/1 in November 1951 in a Tenne~see tailwater caused no
apparent signs of distress in trout (Pfitzer 1962): Baker (1959) found
low dissolved oxygen and distressed fish directly below a dam in
Arkansas in the fall. The oxygen concentration returned to normal and
· ... fish recovered · downstream over the first riffle. Turbulent flows in-
crease the aeration process a .nd thus improve the tailvater habitat -by
increasing dissolved oxygen concentrations.
255. Gas supersaturation has been a major cause of steelhead and
salmon mortality during high-water years in the Snake River, Idaho and
Washington (Raymond 1979). Graves and Haines (1969} stated that'dead
' .
fish vi t~ gas bubbles on their fins were found vi thin 1.6 km of a 'dam
_. i~ N;w Mexico on several occ~sions. · Nitrogen sup~;saturation below a
· ·· ~ntana d~· p~~sisted fo~ ~ome · 32.2 ~ do~stream 'because'· flo.;s in ·tht·· .: ··
tailwater were not turbulent enough to dissipate the nitrogen. Of .39
rainbow trout held in a cage below this dam, 21 died, presumably of
nitrogen embolism .(U. S. Bureau of Reclamation 1973).
· 256. Reproduction. Spawning of rainbow trout has be-en observed
in several cold tailwaters, although survival of eggs and juveniles .is
low. Trout populations in tailwate.rs rely on stocking or recruitment
from the reservoir above to maintain the.ir populations (Ston~ 1972).
Few self-s.ustaining tailwater trout populations that support a fishery
have been reported in the literature. Spawning may occur in tribu-
taries where local conditions a ·re favorable, but the magnitude of
tributary spawning has not been adequate to maintain fishable trout
populations in most tailwaters.
257. The harsh environmental conditions (flow fluctuations, de-
watering) encountered in tailwaters reduces reproductive success.
Corning (1970) found that high flows washed out trout redds. Parsons
7R
...
: :·
:.· . •. .. ,.
(1957) found the 3-m water-level fluctuation in a Tennessee tailvater
from Oc tober through December detrimental to trout reproduction . Redds
ve.re consistently scoured out at high flows and stranded on dry shoals
during low flows. Rainbow trout spawning in December and January vas
common on shoals and riffles, in an Arkansas tailvater, but vater-le.vel
tlu~t·uation caused rolling gravel and destruction of redds. Spawning
in tributaries vas successful, but the contribution of naturally pro-
duced f.ish to the trout fishery in tailvaters vas insignificant (Parsons
1957; .Baker 1959; Pfitzer 1 962). Lov trout populations in the
Beaverhead River, Montana, were caused by poor reproductive success due
to low .flows. Spring and winter dewatering (low flows) of the r i ver ·
caused by. irrigation storage reduced egg and larvae survival. by de-
creasing the cross-sectional area and water velocity of the stream
(Nelson 1977). Corning ( 1970) found that J.ov flows exposed trout redds
to the air and increased siltation, thus reducing egg survival !"rom 85
percent to only 17 percent. Siltation filled the int erstices of the
substrate and smothered the eggs . Schmidt and Robards ( 1916) suggested'
·. . -:-. -· . ._
. staged flows in an Alaska tailvater to clean the substrate and increase
trout and salmon spawning and rearing habitat.
258. Spawning of trout is common in a W)roming tailvater, but the
lack of cover reduces survival of fry. This tailvater relies o.n an . . . . .
annual stocking of 348 rainbow trout fingerlings per hectare to main-
tain the fishery (Mullan et al. 1976). Mot'fett (1942) recommended
stocking of 30,000 fingerling rainbow trout (127 to 178 mm long) per
. ..... · ~ ........ :~ .. _... year to compe-nsate for low repr od.uction caused by vater-level f l uctua-
tions in a tailvater in Nevad.a a:nd Arizona .
259. An obvious effect of dam. construction is the bloc.kage of
.fish migration upstream to spavn.ing grounds. Construction of a dam
on a California river, impounded 50 percent of the salmon spawning
a r eas (Moffett 1949). Attempts to mitigate loss of spawning areas by
hatchery construction have been only partly successful, particularly
for anadromous ·species (Raymond 1979). When a hatchery for Bal ti.c
salmon vas proposed for Narvskaya tail water in the U.S.S.R. to replace
inundated spawning gro·unds, Be.rannikova ( 1962) argued against the
79
hatchery because he beli.eved the high number or predators in the
tailwater would devastate the yearling salmon. Striped bass and saugers
are significant predators on small trout stocked in some tailvaters
during certain seasons (Boles 1969; Ari zona Game and F i sh Department
1972; Deppert 1978).
260 . Food . Food studies have been completed on trout from a
.number of tailwaters and it is apparent that thei r diet is very di verse
(Table 1). Cladoohora beds are an important food source for trout in
ta'ilvaters (Moffett 1942; Mullan et al. 1976). Trout graze on thes.e
mats and ingest the algae and the isopods, simulii.ds, and mayflies
harbored therein. In some tailvaters, food organi,sms hav e been intro-
duced to provide food for trout. Snails were introduced below Glen
Canyon Dam, Arizona, and amphipods were introduced into Taneycomo Lake,
Missouri (Table Rock tailwater) (Mullan et al. 1976; Ralph Burress,
U. S. Fish and Wildlife Service, personal communication).
261. Trout are no·r totally dependent on. food production vi thi.n
the tailvater. In Dale Hollow tailwater, Tennessee, 81 percent -of the
organisms in rai nbow trout stomachs were cladoc.erans which were ··pro-
'· duced in the reservoir above·(Li ttle 1967) •. In this same tailvater,
rainbow trout weighing from 1. 8 to 2. 3 k g ate crappi es 102 to 152 mm
long vhich had been stunned when they pas.sed through the dam (Parsons
1957). R~inbow trout belov Center Hill Dam, Tennessee, .fed heavily on
51-to 76-mm threadfin shad which had passed through the turbines
(Parsons 1957). In Wyman tai.lvater, Ma i ne, rai nbow trout over 4o6 DID
long were more piscivorous than smaller trout. Smaller t .rout ate
Chironanidae (dipterans) which were produced in the reservoir and
carried into the tailwater (Trotzky 1971).
262 . Food organisms eaten by rai nbow trout collected below a
r eservoir d i ffered from that of fish 48.3 km downstream (Welcn 1961).
Algae vere the primary food below t_he dam, and mayflies and small
s,ton.eflies farther downstr eam. The influence o.f tailvat.er flow and
t .emperature on food avai1'3.bility decreases downstream as tributary
inflow, meteorological cond itions, and other influences moderate the
effects of the discharge . Brown trout that were collected immediately
8o
Tailvater
Boulde:r (Hoover) Nev., Ariz .
Canyon, Tex.
Canyon, Tex.
Cente.r Hill, Tenn.
Cow Green, U.K.
Dale Hollow, Tenn.
Dale· Hollow, Tenn.
Dale Hollow, Tenn.
Davis, Nev., Ariz.
Flaming Gorge, Utah, Colo.
Fontenelle, Wyo.
Glen Canyon, Ariz.
'•
·:· .
• < .. -.
··Table 1
Food of Trout in Tailwaters
Food item
Cladophora, mayfly, midge larvae
Ephemeroptera, Diptera, Trichoptera
Ephemeroptera, Diptera, Trichoptera,
terrestrial insects
Threadfin shad
Ephemeroptera, terrestrial insects,
zooplankt on from reservo:f.r
Cladocerans, Diptera, Mollusca,
terrestrial insects, isopods
Cladocerans
Algae, gastropods, Chironomidae,
terrestrial insects, sow bugs,
crayfish·
Detritus
.Algae ·.~·
Cladophora, fish, Daphnia, copepods
Algae, cladocerans, i:ntroduce~ snails
(Continued)
·.
Reference
Moffett 1942
Butler 19'13
White 1969
Parsons 1957
Crisp et al. 1978
Little 1967
Bauer 1976
Parsons 1957
Fast 1965
Mullan et al. 1976
Mullan et al . 1976
Mullan et al. 1976
;.
Co
1\)
Tail water
Glen Canyon, Ariz.
Granby, Colo.
Gunnison, Colo.
(several on river)
Narvskaya, U.S.S.R.
Navajo, N. Mex.
Navajo, N. Mex.
Norfoik, Ark .
Tiber, Mont .
Wyman, Meine
• •
Table !;(Concluded)
.; ~ ·, ....
J'ood item
... ' .
Snails l· ·'.
Diptera, Trichoptera, Ephemeroptera
Cladophora , emergent insects .·
Gemmaridae, opossum shrimp,
Chironomidae
Midge, black fly, caddisfly, mayfly,
grasshopper, beetles, stonefly,
dragonfly~-, ~nails
Diptera, gastropods, Plecoptera,
Tendipedidae, Ephemeroptera,
fish , algae .
Isopods, amphipods, crayfish, aquatic
insects
-~.· · . .-';·
Simuliidae, algae' (Cladophora)
Trichoptera, mayfly, Diptera,.
terrestrial insects, Plecoptera
~·· ...
·'
Reference
Stone 1972
Weber 1959 .'
Mullan et al. 1976
Barannikova 1962
Mullan et al. 1976
Olson 1965
Baker 1959
Welch 1961
Trotzky 1971
J ·": ••• ,
; ......
••• t
. ,.
: .. ·····:··
-~ . . .
•
•
below a reservoir in Colorado a.te more. dipterans (small-bodied insects)
than those collected downstream, whic.h ate primarily trichopterans and
ephemeropterans (W'e'ber 1959).
263. Food is rarely limiting on the trout populations in cold
tailwaters because of natural food production within the tailwater and
food exported into the tailvater from the reservoir above. Fbod orga-
nisms exported from the reservoir display seasonal abundance patterns;
quantities available· in the tailwater are greater during spring and
autumn than during midsummer and winter.
264. Age and growth. Trout grovt.h in tail waters is variable, · ··-..... -•...
generally being comparable to that in reservoirs and often exceeding
that in natural streams (Welch 1961; Trotzky 1971) • The average
length of rainbow trout captured below Blue Mesa Dam, Colorado, in-
·. creased from 246 mm be'fore impoundment to 285 mm after impoundment
· (W'ilt~zius 1978).
265 ~ Rapid growth of rainbow trout stocked in tailvaters has been
reported in & number of studies. Mullan et al. (1976) reporte~ that
~ ~ ' .
stocked fingerlings averaging 191 mm long grew 76 to 102 mm. per year in .
Glen Canyon tailvater, Arizona; 76-mm fingerlings grev to 254 mm in
length in one year in Flaming Gorge tailvater, Utah; and 76-to 127-mm
fingerlin(iis grew to 254 to 381 mm in length in Fontenelle tail water,
'Wyoming. Rainbow trout fi~erliilgs. released at an average length of
83 mm· grew.l78 mm from July to December in Navajo tailvater, New
Mexico (Ol~on· 1965). ·stevenson (1975) reported that the average length
of rainbow and brovn· trout-below Yellowtail Dam, Montana, increased
152 mm between May and December •
. _,., 266. The abundance of food organisms coming from a reservoir and
of 'inv~rtebrates produced in the tailvater is associated vith rap~d
growth of trout. Parsons (1957) stated that rainbow trout in Center
Hill tailvater, Tennessee, fed on thre11.dfin shad· coming through the dam
and grew 25 mm per month. The availability of the higher quality food
·(fish versus insects) in Center Hill. tailwater apparently produced the ·
rapid growth. Rainbow trout growth decreased in Dale Hollow tailvater,
Tennessee, in 1953 and 1954 when the number of fingerlings stocked vas .·
· .. . . .
, ....
..
inereased·from 20,000 to 30,000. This indicated high utilization of
available food in the tailwater. Temperatures in Dale Hollov tailvater,
vhieh range ~rom 7 . 2 to 13 . 3°C vi t.h a maximum monthly variation of
1.7°C, are considered excellent for trout growth (Parsons 1957). Rain-
bov trout that fed on the large numbers of arthropods harbored in the
vegetation in Norfork and Bull Shoals ts.ilwate:r"s, Arkansas, during 1957,
grev 23 mm :per month. In 1958, vhen flood flows washed out .much .of
this vegetation, trout growth decreased to 17 mm :per month (Baker 1959).
· 267. Trout growth in tailwaters and other areas bas been discussed
by several authors. Irving and Cu:plin (1956) re:ported only small dif-
. ferenees in g~ovth of native and stocked rainbow trout ca:ptured in ... ,.. ..··
several Snake River tailwaters:
.··· ..
Total length, mm
~ Native fish Hs.tcher;r fish
I 130 127
II 262 244
.-. III 351 .. 333 . . • ,,;•\' .. IV 467 445
v 488
Also, no differences in growth could be sh~ f pr rainbov trout take~
·. .
f:r.om ,"t;ai1vaters or im:polll\d.ments on the Snake River, Idaho . Trotzky
, ... · ...
(1971) found that rainbow trout in Kennebec River tailvaters, Maine,
grew. f~.ster than rainbow trout in streams and lak.es ·from other areas
of the United ·States. Large trout have been reported from several
tailwaters . Rainbov and brovn trout veighing ·6.8 kg have been captured
in the White River tailwaters, Arkansas (Baker 1959), and trout u:p to
5.5 kg are commo n in Fontenelle tailvater, Wyoming (Banks et s.l. 1974).
268. Reduced water temperature ereremes in vinter and summer and
a more homogeneous temperature regime throughout the year appear to
have resulted in year-round growth of ra.inbov trout in some tailwat.ers .
This eo~clusion is supported by the inconsistent age :readings and lack
of annulus formation on scales of trout from some tailwaters (Moffett
84
•
•
,
1942; Parsons 1957; Pfitzer 1962; Olson 1968). In Watauga tailvater,
Tennessee, where winter water temperatures are moderate, year-round
growth of rainbow trout averaged 15 mm per month. Little or no fish
growth vill occur in tailwaters where vinte:r water temperatures are
extremely cold.
Esod.dae (Pikes)
269. The.re are four spedes of the pike family in North America:
grass pickerel, chain pickerel, northern pike, a.nd muskellunge. The
natural range of the_ chain and grass. pickerels is the eastern United
States; whereas, that of tbe northern pike is north-central United
States and Canada, and taat of the muskellunge is the Great Lakes
stat.es south to Kentuclr.f. Northern pike and muskellunge reach a large
size and. are highly regarded as game fishes. Both specie.s or their
hybrids have been stoc ked extensively in some reservoirs. The chain
and grass pickerel are smaller fi.sh and though chain pickerel provide
· ·, f fishing in som.e streams, gn'.ss pi~ke.rel seldom .reach catchable ·size. •,
.. The pickerels occur in SO!l'.e tailwaters, but they receive littl':! mention
in the literature' and vill not be discussed further.
~
270. Habitat. All pikes have similar requirements in that they
prefer clean, quiet-water areas of lakes and streams where there is an
abund..an.ce of aquatic vegetation. In streams, they prefer cove.r along
the margins in patches of vegetation, beside submerged roots or
branc·hes, or in patches of shade. Northern pike are commonly found in
a variet.y of habitats in lakes, reservoirs, and large streams , and
muskellunge in lakes and pools and backwaters of slow-moving streams.
271. Reoro duction . Pikes spawn in the spr:ing soon after ice-out.
They move. into marshes or other shallow marginal waters vher·e vegeta-
tion is abundant. No nest is built, and eggs are broadeast and aban-
doned. The adhesive eggs sink and adhere to the bottom or to vezP.ta-
tion. They hatc·h in 10 to 14 days, and the larvae remain inactive but
attached to vegetation for 6 to 10 days or until the yolk sac is
absorbed. Both eggs and young may be stranded if water levels drop in
the shallov breeding areas. Studies suggest that spring water levels
must remain high for at least a month afte.r pikes spavn to obtain good
year-class survival.
272. Food. Pikes are carnivorous, feeding principally on other
fishe.s. They remain motionless near cover and dart out t,o capture
unwary· passing prey. Pike larvae eat zooplankton and the. larger young
eat aquatic insects and small fish.
273. Age and growth. Grovth of both the northern pike and
muskellunge is extremely rapid. Norther.n pike average 251 mm long at
the end of their first_year and 777 mm at the end of their sixth year
(Karvelis 1964). The maximum length of male.s probably does not exceed
760 mm (Threinen et al. 1966). Maximum length of females may exceed
1016 mm, bu.t fev survive beyond 12 years. Muskellunge. average 267 mm
long at the end of their first year and 769 mm at the end of 5 years
(Karvelis 1964). Maximwn age is about 20 yeal's, and maximum repol'ted
length is in excess of 1270 mm. For all species or pike, females grow
'·'·mOre rapidl.y and live longer than males.
or 3 years old.'
Pikes in tailvaters
Most .fisb are mature vhen 2
274. None of the pikes are common tail waters. They may be found
there for several years after construction of a reservoir on. rivers
vhe.re the species occurs naturally or after stocking within the. reser-
voir. They may move upstream into tailwaters from downstream locations
at certain'ti.J;les of th~? year to feed or spavn •
. 275. Most. north~rn pike and muskellunse found in tailwaters have
passe~ over or through a dam from the reservoir above (Diuzhikov 1961;
Hanson 191'7; Wilt:.ius 1978). During or immed.iatly after the filling
of a nev reservoir, pike may become common in the tailvater for a short
period!. Di'-!zhikov (1961) reported large year cla.sses of pike being
produced in Kuibyshev Reservoir, Volga River, as it wa.s being filled.
Many of these fish passed over the dam and congregated .in the
tailwaters, feeding on the large. numbers of small fi.sh t 'hat passed over
the da:n or vere blocked during upstream migrai.iuns. During the tvo
86
•
. .
-'
....•. ~
to three years following impoundment, up to 40 percent of the number
and 90 percent of the biomass of fish caught in the tailvaters were
pike. Th.ese high catches were followed by .a rapid decline in numbers
within 5 years {Chikova 1968).
..
276. The loss of p.ike from. Kuibyshev tailvaters can be attributed
to both reduced reproduction in the reservoir and la~-k of spawning
success in the tailwater. Spawning in. the tail water vas delayed from
early May to late May because of slower warming of water and high daily
and. weekly vate.r-level fluctuations caused by hydropower production,
which further inhibited spawning. Additionally, a seasonal drop in
water levels of 4 to 5 m occurred during embryonic development, re-
sulting in massive desiccation of the deposite'd eggs and larvae
{Eliseev and. Chikova 1968).
277. A similar situation occurred in Narvskaya tailwaters on the
Narova River, where regular, sharp water-level fluctuations due to
hydropower peaking activity result.ed in the disruption or cessation of
pike spawning. This vas evident .from the large number of ad?lt pike
found to be resorbing sexual products (Ba.rannikova 1962). Dilappear-
anc.e of northern pike from the tailwaters below four hydropower im-
poundments {e.g., Cooke, Five Channels, Foote, and Mio) on the Au Sable
River, Michigan, is believed to have been caused by the lack of spawning
success in the tailvaters, coupled with a general decrease in produc-
tivity of the upstream reservoirs (R_ichards 1976) •.
278. Dams have also effect.ively limited reproduction by blocking
movement of fish to their upstream spawning grounds. This occurred on
the Middle Fork of the Kentuck.y River where muskellunge numbers have
steadily declined since the construction of Buckhorn Reservoir,
Kentucky (Branson 1977).
· 279. The ef:t"ects of flow regulation on pike are not limited to
the immediate tailwaters of certain dams. Reduced river flows result-
ing from reserv oir filling can affect pike distribution and reproduc-
tion hundreds of kilometres downstream. Low vinter flows below Bennet:t
Da:n on the Peace-Athabasca River in Canada during the filling of
W'i.lliston Lake threatened the northern pike populations in Lake
....
.. ··
Athaba.sca through severe freezing of shallow-water areas and increased
oxygen de,pletion which caused a winter-kill {Townsen~ 1975).
280. Similarly, flood control below the Volg'>g:;.-ad hydropower
facility on the Volga River has affected the northern pike population
·in--the delta Oil the Caspian Sea far downstream. The lov \o"ater resulting
from spring flood control has shifted the pike's distribution vi thin
the delta and. bas caused a. delay in the spal.~ing season from March-April
to May ,and a corresponding decrease in spawning success. The delay in
spavning shortened the foraging season, and pike grovth ·rates declined. '···. .. .
·Additionally, the reduction in numbe,rs of the pike's prime forage
species, mai nly ·spring spawning vobla, pike-perch, and bream, resulted
in a decrease of its annual food supply (Orlova and Popova 1976).
Cyprinidae (Minnows)
281. The minnow family is the largest of all fish famil.ies. Most
m•bers are small, but some (carp, squavf'ish, chubs) attain large size.
Minnows are found in all natural wat .ers, but are more common in streams
than in lakes or ponds. In s t reams, they are often more numerous than
all other fishes combined . Minnows are efficient in transforming
minute aquatic food into sizable food for larger game fishes .
282. As a group, the c.yprinids vary greatly in. food babi ts; some
feed on insects, some on algae, and some on the organi.c mud of the
bottam;··st-ill others are omnivorous: Habitats may include silty, clear,
a~·. bog waters; quiet or rapidly fldwi.ng streams; sand, mud or gravel
bottoms.
283 . Spavning migrations by minnows. are limited; no species moves
more than a short distance upstream, or beyond the shoals of a lake.
All spavn in spring or summer and the incubation period of the eggs is
relatively short. Some species merely sca.tter thei.r · eggs in a sui table
habitat; others deposit th!!lll 'in specially prepared nests; and still
others guard the eggs until they hatch.
284 . Many different species of minnows often occur in the same
waters. In such instances, the various species are found over
88
different types of bottoms: mud feeders over mud bottom, algae feeders
over algae-covered rocks, and insect feeders over sand and gravel or
other types of bottoms.
285. With the exception of carp and some chubs, minnows are not
sought by sport fishermen. Most minnows are effective baits for the
taking of sport fishes. Because of the large number of minnow species,
this discussion of life histo-ry is limited to the following general
cyprinid groups: carp, chubs, true minnows, • shiners, and stone roller's.
Spec.ies considered. vi thin these groups are those most often mentioned
in tail water literature. Discussion of cyprinid occur.:rence in
t&i.lvate-rs includes the above five groups plus daces, squavfishes and
chiselmouths, and cyprinids in Russian tailvaters. Daces, squavfishes,
and chiselmouths are of local importance, and Russian cyprinids are
included. to illustrate tailvater-fish problems simi.lar to those found
in the ~nited States.
~
-286. Habitat. Carp are found throughout the United States. The • _. -,·r • •,
species is very adaptable and occ.urs in most aquatic habitats b\it is
; .
most COIIIIDOD in large streams, lakes, and man-made impoWidments that a.t:-e
highly productive because of natural fertility or organic pollution.
In streams, adult carp are usually found near submerged cover such as
brush piles or logs and where the current is the slowest. In lakes and
reservoirs, carp e.re usual.ly found near shore or in shallow embayme.nts;
an occasional fish may be found in depths exceeding 10 m.
287. Carp do not school, but they ·do form lo.ose aggregations.
The species is not considered migratory, but some individuals move for
· long distances. Where carp be.come abundant there is usually a general
deterioration of the habitat because of increased. turbidity and destruc-
tion of aquatic vegetation caused largely by the fish's feeding habits.
288. Reuroduction. _Carp move into shallows to spawn between late
March and late June. Spawning starts at va.ter temperatures of 14.5 to
*Members of the family Cyprinidae whose common name includes the
word "minnow" (Bailey et al. 1970).
89
. ~.
.. ··
I~
'I I
17°C but peaks at 18.5 to 20°C. The eggs are scattered over logs,
rocks, or submerged vegetation . Eggs ha.tch in 4 to 8 days, depending
on temperature; there is no parental care of eggs or fry. Carp o.ften
spa'Wll in water so shallow that their backs are exposed and the noise
created as they thrash abc•1t can be heard for considerable distances .
289. Food. Carp fee.i on a variety of an.imal and plant mate.rial.
Aquatic insects are the most coDDDon diet item and plant material ranks
second. Most active feeding occ~s in late evening or early morning
and food is probably located more by taste tha:n by sight. Carp are
mostly bottom feeders, but they have also been observed taking floating
objects en the .water surface.
290. Age and grovt h. According to Pfli eg·e:r ( 1975) , carp in
Missouri streams average 165 l!llll long at the end o·f their first year o f
life and reach lengths of about 279, 361~ 424, and 457 mm in succeeding
years. On the average they veigh 0.45 kg when 305 nun long, 2.3 kg when
546 mm long, and 5.4 kg when 698 mm long. Carp from cool, infertile
vate~s grow more slowly and veigh less at comparable lengths than do
those from warm, productive waters. Few live more than 12 years. Most
•.
males are mature at ages II-IV and most females at ages II!-V. · ·
CarP in tailvaters
291 . Carp are common to abundant .in many varmv~ter tailvaters.
Tbey were 'abundant in the anglers catch in Lake of the Ozarks from
1965 to 1974 and were 6 percent of the catch ~ 1964 in Clearwater Dam
tailvater, Missouri (Hanson 1965, 1977). Carp made up 57 percent of
the 'fish captured by anglers in 1968 in Carlyle tailvater, Illinois
(Fritz 1969), and. constituted the bulk of the weight of fish collected
in Holyoke Dam tailvater, Massachusetts (Jefferies 1974). They were
also numerous below Fern Ridge Reservoir, Oregon {Hutchison et al.
1966).
292. Carp have also adapted well to conditions in a number of
cold tailvaters. Creel surveys in Kentucky on the Barren Reservoir
and Nolin Reservoir tailvaters from 1965 through 1971 recorded catches
of carp rangi.ng from 1,300 to 6,200 and 143. to 10,000 fish, respec-
tively. These catches accounted for 3 to 30 percent of the total
90
·•
. • ...
' ;
....
•• ~· •:. I
..
sport fishing catch on these tailvaters during those years (J. P. Carter
1968a; Charles and McLemore 1973). In addition, carp composed 50 per-
cent of the fish population (estimated from samples collected by
electrot'ishing) in Nolin Reservoir tailvater in March 1966 (J. P. Carter
l968a). Carp are abundant in Chilhowee and Norris tailwaters,
Tennessee (Hill 1978). They are one of the dominant species in Dale
Hollow tailwater, Tennessee (Bauer 1976). Though not numerous in the
immediate tailvater, carp were found to make up 18 percent. of the fish
population 48.4 km downstream below Cumberland Dam, Kentucky (Henley
1967). Carp are commonly found in angler catches in a series of
tailwaters on the Snake River, r daho, including Lower Salmon Falls,.
Bliss, and C. J. St.rike (Irving and Cuplin 1956}. Holden and St~lnaker
·(1975) also re•ported carp as common be-low Glen Canyon Dam, Colorado. Not
• .....
·all cold tailvaters continue to pro!id~ good carp ,habitat! Carp. h&ve.····, ....
decreased in abundance in a Wyoming tailvater, apparently because of
declining temperatures (Mullan et al. 1976).
293. · Dam construction has limited the distribution of carp. The
upstream migration of carp out of some Tennessee reservoirs has been .:;
., blocked by mil.l dams. This helps maintain t .he populations of small.::; --. .
. mouth bass and. other game fish in these streams by limiting competition
(Ruhr 1957). In the Kennebec River, Maine, carp have been kept out of
the productive upper river by the presence of Augus~a Dam (Foye et al .
1969).
294.· Successf'ul. carp reproduction may occur in tailwaters, but it
has not been verified. Running ripe c.arp we·re caught in Lewis and ··
Clark tailwater, South Dakota a n d Nebraska, at temperatures of 22°C,
· and spent females were found after temperatures of 25°C were .reached.
No young-of-the-year carp were collected from this tailwater (Walburg
et al. 1971} .
295. Most recruitment of carp to tailvaters appears to come from
the reservoir above or the river downstream. Large numbers of 'young-
of-the-year carp-as ms.ny as 310,000 in 24 .hours--were found in the·
discharge at. Levis and Clark Lake, but these fish did not stay in the
'tailvater (Walburg 1971; Walburg et al. 1971). Adult. carp were the
91
second most numerous species lost over the spillway at Little Grassy
Lake, lllinoi-3, amounting to 14 percent of the total fish transported
into the tailvater (Louder 1958).
296 .. Food habits of carp in ta.ilvaters were examined only below ..
Levis and Clark Lake. Zooplankton, algae, and bryozoans were all
utilized. ZooplaDkton was the main food available during the period
vhe_n carp were most abundant, from early spring through July (Walburg
et al. 1971). ·
297. Carp grow well in most varmwa.t er tail waters. The average
ve.ight of carp taken by anglers in Car lyle tail water, Illinois, vas
. 0.66 kg _in 1967 and 0. 50 kg in 1968 (Pritz 1969). The average weight
or this species collec.ted in Canton Reservoir stilling basin, Oklahoma,
vas 0.50 kg (Moser and Hicks 1970). Carp collected in Lewis and Clark
tailvater averaged 8 percent larger than those from the reservoir
(Walburg et al. 1971).
~
298. Habitat. Most species of chubs inhabit clear. streams having
penaanent flov and a predominanc.e of clean gravel or rubble -bottoms. _., _'.
'Adults -&re usually found near riffles or in Jiools but not in the
swifter current. The young are usually found ill qui.et:-vater areas 8J:1.d
most often in association with higher aquatic pl~ts.
299. Re.production. The following description of spawning _by the ·
hornyhead chub (Scott and Crossman 1973) is believed typical for stream
chubs. Spawning takes place in the spl_"ing of _the yeS!, probably when
water temperatures reach about 24°C. Nests of stones and pebbles are
built by the males on a fine-gravel or pebble bottom, often below a
riffle, and in relatively shallow water that covers the top o'f a com-
pleted nest to a depth of 15.2-45.7 em. Nest building is usually
begun after May 15. As construction progresses, females may approach
the, nest and be enticed to it or d.ri ven over· it by the male. Spawning
tak.es place in a few seconds and the female moves quickly downstream.
The re.lee.sed eggs settle among the stones and the male cont~nues to
add more stones to the nest, thus ensuring additional protection for
the eggs. The nest-building male. carries stones in his mouth or rolls
92
..
: .... _,.-..
.. -.. · ..
' -~ .-
·~.
.·
and pushes them with lips and snout. The total egg complement is not
deposited in one nest at one time, since at each spawning a female
deposits only ripe eggs. As many as 10 females may spawn in one nest.
The nest mou:nd incr~ases in size as more stones are added by t .he male
after successive spawnings. The sizes of nests are irregular and vary
from. 30.5 em to 91.4 em vide, from 61.0 em to 91.4 em long (with the
current), and from 5.1 to 15.2 em deep. The nesting sites may be used
as spawning grounds by other species of minnows, even while the chub is
still using the nest.
300. ~ Young chubs feed on cladocerans, copepods, and
chironcmids. Adults eat mainly immature and adult aquatic insects,
terrestrial insects, crustaceans, and plant material. Crayfish, vorms,
and mollusks are also consumed by som.e species.
301. A.ge and grovth. The ultimate size attained by chubs varies
with the genus. Total lengths of adults are generally 65 to 75·mm in ·
some ge:nera and 100 to 200 mm in others. Maximum length ranges from
90 mm for some genera to 260 mm for others. Males groW' tnore rapidly
· ... · than teauues and rea.c.h a larger .maximum · si"ze. • · ,.
Chubs in ta.ilwaters
302. The common name "chub" is used for fish of several genera.
This discussion is limited to chubs from the genera Hybopsis, Gila,
~loc heil us , Nocomi s ., and Semot il us .
303. The various chubs respond differently in tailvater environ-
ments and their presence or absence depends primarily on the charac-
teristics of the particular. tailvater. In Tennessee, the river chub
(Nocomis microPOgon) is abundant in the coldwater Apalachia and
Chilhowee tailvaters, vhere it is used as forage by other fish species
(Ptitzer 1962; Hill 1978). This chub bas disappeared from the Grand
River below Shand Dam, Ontario, but it remains common in the river
above the reservoir.· Delay of the spawning season because of a 7°C
decline in m&Ximum temperature, from 28°C above the reservoir to 21°C
in the tailvater, is cited as the reason for the river chub's dis-
appearance (Spence and Hynes l97lb). The river chub has also dis.-
appeared from the warmvater tailvater·s below tour hydropower
93
··-... .. '
..... ·•
..
j
!:
impoundments on the Au Sable River, Michigan (Richards 1976), but the
reason for this disappearance is unknown.
304. The roundtail chub (~ robusta) is found below Blue Mesa
Dam, Colorado, and has apparently suffered no ill effects from the
reduced temperature and turbidity in this tailwater (Mullan et al . 1976;
Wiltzius 1978). However, this species of chub appears to be disappear-
ing from a tail vater in New Mex i co (Mullan et_ al. 1976) •. In & tailwater
in Utah and Wyoming, t .he round tail chub did no~ reproduce in two of
three years following impoundment, presumably because or the reduction
·of summer water temperat.ure from 8. 3 to 2. 8°C that resulted from in-
creased summer hypolimnetic discharges in 1964 and 1966 •. -. The growth
~ •• ~ ''o I 'II o ... -·· • : • o I o o
rate o f this speci es has also declined since impoundment (Vanicek and
· Kramer 1969). ·· The similar bonyt.a.il chub (Gila elegans) , once con-
sidered a_ subspecies of the •oundtail chub, has disappeared from~
cold tailwater in Wyoming because water temperatures and turbidities
suitable for this spec·ies no longer occur (Mullan et al. 1976) • . '
. 305. The humpback chub (Gila CYJ>ha) :was occasionally found in. an
Arizona tailwater in 1967, but .by 1973 numbers of this. specie~ in .this
~old tail water h~d further declin~d, most lik-;~Y beca~se of habitat'_::; i
changes resulting from dam construction and operation (Holden and
Stalnaker 1975).
306. The hornyhead chub (Nocomis biguttatus) has a large popula-
lation in the cold tailwater below Hoover Dam, Ohio, where temperatures
r~~ge from 14 .4 to 21.7°C. Overcrowding in the tailwater may be aiding
expansion of this species in the drainage, where it was rarely found
before impoundment of the reservoir ( Cave.nder and Cru:rik:H ton 1974).
Spawn i ng delays caused by the 7°C t .emperature reduction below Shand Dam,
Ontario, have eliminated the hornyhead chub from this tailwater . This
species is one of the more common cyprinids above the reservoir (Spence
and Hynes 197lb).
307 . The creek chub (Semotilus atr omaculatus) has thrived in cold
tailwaters. It is common in Hoover tailvater, Ohio (Cavender and
Crunkilton 1974), and in the tailwater below Granby Dam, Colorado, in
spite of a reduction in flows to only 11 percent of the hist orical
94
: ~.
.. ~·
.• ..
.. ~ . ..........
·:·· .-; ...
·.·
average (Weber 1959). Cold wate.r temperatures appear to have aided the
creek chub in Shand Dam tailvater, Ontario. The. species has continue.d
to reproduce successful.ly.here, whereas the reproduction of other
cyprinids has ceased. This has allowed the creek chub to become numer-
ous in the tailvater, although i t i nfrequently occurs above the ~eser
voir (Spence and Hynes 19Tlb).
3o8. A 6-to 8-week delay in spawning caused by reduced tempera-
tures bas leci to a decline in the reproductive success. and numbers of
the peamouth chub (Mylocheilus caurinus) in a r.fontana tail water (~!ay
and Huston 1979). The peamouth chub occurs and is occasionally creeled
in the cold tailvaters belov Upper and Lover Salmon Falls dams, Bliss
Dam, and C. J. Strike Dam in Idaho (Irving and Cuplin 1956).
309. The streamline chub (Hybopsis dissimilis) vas collected in.
Barren Reservoir tailvater, Kentucky, during an electrofishing survey
in March 1966 (J.P. Carter 1968a). The speckled chub (Hybonsis
~es.t ivalis) has disappeared ~om a cold tail water i n Texas, although it
vas found in t he vicinity of the dam during: preimpoundJDent surveys and
still survives in the river above the reservoir (Edwards 1978). Cold
water temperatures and other .factors in the tailvater, caused by
hypolimnetic releases, are most likely responsible for loss of this
fish •
310. Reduced turbidity in tai~vaters may benefit some chub
species. The turbidity-int olerant bigeye chub (Hybonsis amblons) is
occasi onally found in Hoover Dam tailvater, Oh i o, perhaps due t o
sl.i:glrtly lower tUl'bidi ty .levels .. _.This species is .seldom t:ound in the ·· "·"' .,.-"'"'"
rest of the Big Wal nut Cr eek drainage (Cavender and Crunkil ton 1974) ·•
· .. · ... 311. Bec·ause of 'the · lat-ge number of c hub · species and the wide
.r·. · ~ange of their environmental requirements, generalizations on their
success in tailwaters is difficult. Temperature changes and their
effects on reproduction, along with changes in turbidity, appear to be
··most important in determining the p ·resence or absence of chubs.
True minnows·
312. Habitat. The true minnows are a diverse group .vi th a variety .
of habi tat preference. Many pre.fer lakes, ponds, or backwaters of
95
slow-moving streams with dense vegetation. Few species are found in
reservoir tailwaters . They are tolerant of turbidit y as long as there
is enough current to keep riffle areas free of silt. Many occur in
. sc~ools n ear the river bottom, but they avoid-strong current.--
313. ReProduction. Most minnovs spawn. between April and July.
Some randomly spawn in shallow areas above gravelly or sandy riffles
and others over silt bottoms; still others prepare nests in sand. or
gravel areas which are guarded by the male. The following description
for the bluntnose minnow (PimePhales notatus) taken from Pflieger
(1975) is fairly typical for nest-building minnows.
314. The bluntnose minnow has a long spavning season, extending
in Missouri fr::>m early May, when water ·temperatures are at least 20°C,
to about mid-August. The peak of spawning is in late May and June.
The eggs are deposited on almost any object (flat stones, boards, logs)
that has a flat undersurface and lies on the bottom at depths ef 15 to
90 em . Usually sand or gravel, rather than a mud bottom, is selected
for a nest site. Nest construction consists of excavating a small
cavity beneat h the object selected and cleaning the undersurfac.es where
the eggs will be deposited. In excavating ttie cavity, silt, fi'ne sand,
and pebbles are svept away by violent motions of the tail fin, and
larger objects are. pushed out with the tuberculate snout. The roof of
the cavity is cleaned by the male with his mouth and the spongy pad on
his back. · Only a sihgle male occupies a nest, but several males often
nest in proximity beneath a single object. Several females may spawn
in a single nest, vhich may ultimately contain more than 5000 eggs ,
Eggs hatch in 6 to 14 days, depending on water temperature, and. nevly
hatched young are about 5 mm long . The male remains on the nest
throughout the incubation period, driving away all other fish except
females ready to spawn .
315. Food. The food of the mi ·nnovs is1 generalized and, includes
both plants and animals; aquatic insects., small crustaceans, and algae
predominate.
316. Age e.nd growth . Lengths of adult minnows generally range
between 50and 75 mm, and maximum lengths betveen 75 and 100 mm. .Most
average about 50 11111 long at end of first year of life and 75 mm at the
end of the second. Few live longer than 3 years. Most are sexually
mature in their second summer.
317. Males grow more rapidly and to a larger size than ·females
for minnow species in which males guard the nest. Females are usually
larger in species that do not guard the nest.
True minnows in tailvaters
318. Seven genera of Cy}:)rinidae are commonly termed "minnows"
(Bailey et al. 1970}. Two genera (Pimenhales and Phenacobi us) that
reportedly occur in tailwaters are discussed in this section.
319. The fathead minnow ( Pimephales. nromelas} has a vide tempera-
ture tolerance which makes it well-suited to the tailwater environment .
It has increased in numbers in both the Navajo tailqter, New Mexico,
and the Fontenelle tailwater, Wyoming (Mullai1 et al. 1976}. The fathead
minnow is one of the remaining native species in cold Granby Dam
tailwater, Colorado, where flows are only 11 percent of the historical
average ('Weber 1959). The fathead minnow is the third most abundant
species in the warm tailvate.r below Lake Carl Blackwell, Oklahoma,· and
spawing activity was indicated in .mid-April when water tempera.tures
reached 17°C (Cross 1950). The fathead minnow also occ·urs in Hoove'I'
tailwater, Ohio . It apparently passed over the dam from the :reservoir
above where it had been introduced as a bait fish (Cavender and
Crunkilton 1974). This species vas also introduced into Dale Hollow
tailvater, Tennessee, probably through its use as a bait fish (Bauer
1976).
320. The suc cess of the bluntnose minnow (Pimephales notatus) in
cold tailvaters is varied . It is found in the cold Barr en Reservoir
tail water, Ken t ucky (J. P. Carter 1968a) and is common in the drainage
of Bi g Walnut Creek, Ohio, including Hoover Dam tail water (Cavender
and Crunki lton 1974). The 'blunt nose minnow bas disappeared from the
Grand River below Shand Dam, Ontario, presumably because of lack of
spawn i ng ca.-used. by temperature reductions, since the spec.ies is com-
monly found in the drainage above the reservoir (Spence and Hynes
197lb).
97
321. The bullhead minnow (Pimephales vigilax) vas present in the
cold tailvaters below Canyon Dam, Texas, in 1976, but vas not collected
from the river above the reservoir. No explanation vas apparent for
the absence of this species in the 1976 collections above the reservoir
since it had been collected here in othe·r years (Edwards 1978).
322. Adult suckerrnouth mi:mows ( P.henacobi us mi rabili s) we·re abun-
d~lt in the river below Lake Carl Blackwell, Oklahoma, only during the
· spawning season. Females in spawning condition occurred in pools below
the dam in April at water temperatures. of lli to 25°C. Young of the year
were abundant by mid~une in shallow· running water. By mid~uly, young
suckermouth minnows had reached a length of 41 mm and vere only found
in the s.wiftest flowing waters below the dam (Cro:ss 1950).
323. In three papers on tailwaters, minnows wer_e referred to in
oniy general terms, without actual species being indicated. Pfitzer
(1962) noted a general loss of minnow species in the cold tributary
tailwaters of the Tennessee Valley. Diversity of minnow species de-·
creased following the completion of a hypolimnetic release dam in
Wisconsin in 1967. Although 8 to 10 minnow species were present at the
three study stations belo.w the dam from 1965 to 1968, only 4 to 6
species vere found in 1969. Also, there vas a dec.rease in the overall
abundance of minnows in this tailwater (Wirth et al. 1970). The
authors ga:ve no reason for the observed minnow popltlation changes,
although it would appear that cold va.ter temperatures were responsible.
Mi.nnows were numerous in the warm tailvater below Elephant Butte
Dam, New Mexico, 'W'he.re they made up 57 percent of samples collected in
1956 in seines and by electro shocking (Huntington and Navar:re 1957).
Shiners
321!. Habitat. Shiners (Uotro"Ois) are the most abundant species
vithin the Cyprinidae. They are a diverse group and the various
species have a wide variety of habitat preferences. Many are found
only in lakes, po·nds, or backwaters with little current, and others
largely in small headwater streams. Relatively few shiner species are
found in tail waters. s ·hiners in tailwate·rs prefer moderate to large-
sized streams with relatively clear water throughout most of year,
98
...
. . ~-
. ~
'·
.·
moderate or high gradients, and clean sand, gravel, .rubble and or
boulder-strew bottoms. Some species are found in the deep, svif't
riffles and in eddies and currents of pools immediately below such
riffles. Other shiners prefer low to moderate current gradients and
are mos.t abundant in shallow sandy pools. Some are found in schools
in midwater or near the surface, and others near the bottom.
325. Reproduction. Shiners have varied spawning hab·its depend!.ng
on the species. The following description for the common shiner taken
·from Scott and Grossman ( 1973) is generally applical;>le to most shiners.
326. Spawning usually begins when vater temperatures reach 15.6
to l8.3°C, usually in May or June. Spawning may occur over gravel beds
in flowing vater; the fish may excavate shallow nests in gravel i.a .. . ..
flowing 'Vater, or they may use the nests made by other fishes, even
though such nests lack a current flow. They often spawn at the head or
a gravelly riffle where the male establishes a territory. The females
stay on the gravel below the males until ·ready .to spawn, then .move·
upetrea,m and eventually spawn. The spawning act takes place in a
· tractio~ of a second 'and is repeated many times, often· within a 'tf!!V
ainutes, and there may be a constant succession of males and females .
moving onto the spawning · site, spawning, and dropping back. Studies
suggest that few eggs, probably not .mo·re than 50, are released at. each
spawning. Tht! adhesive eo.~s drop to the bottom and become lodged
between crevices of gravel. Eggs hatch in about 2-1/2 days at 21.1°C
and larvae are about 5 mm long •
327. ~ Shiners have generalized food habits. They feed on
aquatic and terrestrial insects, small crustaceans, arui algae. Larger
individuals may prey on small fish.
328. Age and growth. Average length of adult shiners is variable .
by species. Adults of some species range between 45 and 65 mm long and
reach a maximum length of 70 mm; adults of other species range between
75 and 125 mm long and reach a maximum length of 175 mm. Males are
the larger in some species, and females in others. ·Most shiners mature
in their second or third summer; few live beyond age III.
9.9
·.
. '
Shiners in tailvaters
329. The shiners are a varied taxonomic group with many s~ecies.
The majority discussed in this section are members of the g,enus
NotroPis; however, two shiners from the genera Notemigonus and
Richa=-dsonius are also included. ..·
330. The rosy1'ace· shiner (Notropis robellus) appears to thrive in .......
cold tailwaters. It is abunda:nt in Bull Shoals tailvater. Arkansas
~ -·
(Brown et al. 1968; Hoffman and Kilambi 1970), and. is favored in· the
tailve.ter environment below Hoover Reservoir, Ohio, by both the reduced
temperature and the abundance of well-developed·riffles (Cavender and
Crunkilton 1974). This species, togethe·r with the blackchin shiner
(Notrop.fs heterodon) and redfin shiner (Notropis tDDbratilis), bas dis-
appeared in the warm tailvaters below four hydropower facilities on
the'Au Sable River, Michigan (Richards 1976).
331. The mimic shiner (Notropis volucellus) has become a common
species below the same four bydropowe·r impoundments on the Au Sable·
·· Ri~er (Richards' 1976). This shiner has disappeared boca the cold
:'~ Canyo~ Dam_ tailwater in Texas; although it is camnon in the river above
!" the .. r~·servoir (Edvards·I978).' ·. · ' ··· ·: •:., '_-(;;:,:/;. ·: ;,. ·, ·• ...
332. The redside shiner (Richardsonius bait~at.u"s) does W ·ll. i~·.
both varm and cold tailwaters. It thrives in water temperatures up to
26.7°C, which occur in tailvate.rs below dams on the 'Row River. Long Tom
River, and Coast Fork Willamette River in Oregon (Hutchison et al.
1966). It i·s ·abundant in the cold tail waters below Owyhee Reservoir
.and Antelope Reservoir • Oregon (Fortune and Thompson 1969). It also
~ppears to be maintaining its abundance in the cold Fontenell.e . .
tailvater, Wyoming (Mullan et al. 1976).
333. Tne red shiner (NotroPis lutrensis) is fo~~d in both warm
and cold tail waters. It is the most abundant species in Lake Carl ...
Blackwell tailwater, Oklahoma (Cross 1950). Below Canyon Dam, Texas,
it is the third most abundant species. Edwards (1978) believes that
stabilization of va.te:r flows below this dam has increased red shiner
abundance.
100 .
. .
-~
334. The golden shiner (Notemigonus c·rysoleucas) and the spot tail
shiner (Notropis hudsonius) are n.umero.us in. varm Holyoke Dam tailvater,
Massachusetts (Jefferies 1974). In cold tailwaters, the golden shiner
is found primarily due to its introduction as a bait fish. It is found
in Dale Hollow tailwater, Tennessee, and appears to have moved from the
reservoirs into both Hoover tailwater, Ohio, and Canyon Dam tail:water,
Texas (Cavender and Crunkilton 1974; Bauer 1976; Edwards 1978).
335. Large .numbers of young eme::-ald shiners (Notropis
atherinoides)-up to 800,000 in 24 hours--were lost in the discharge
from Levis and Clark Lake, South Dakota (Walburg 1971). In the
tailwater, this species is widely used a .s forage by game f'ish (Walburg
et al. 1971). Thist species composed 16 perc.ent of the fish taken in
Buckhorn tail water and vas also ·taken from Barren Reservoir tail water,
Kentucky, in an electrofishing survey (Henley 1967; J. P. Carter 1968a).
336. The success of the spotfin ~•hiner (Notronis spilonteru:s) in
cold tailwaters is varied. It occurs commonly in both Hoover tailwater,
Ohio, and Barren Reservoir tailwater, Kentucky (J. P. Carter 1968a;
·Cavender and Crunkilton 1974). This shiner has disappeared below Sha.nd
Dam in Ontario due to a delay in spavning cau.sed by cold water temper-
atures (Spence and Hynes, 197lb).
337. A large number of other sl:Uner species occur in cold
tailwaters. The duskystripe shiner (Nc•tropis Ei].sbryi) is the most
abundant cyprinid in .Norfork tailwater, Arkansas. This species, along
with the bigeye shiner (Notropis boons) and the whitetail shiner
(Notropis galacturus), is abundant in Bull s·hoals tailwater, Arkansas
(Brown et al. 1968; Hoffman and Kilambi 1970). In Hoover tailwater,
Ohio, the str~ped sh.iner (Notropis cbrysocephalus) is abrmda:nt, while
a species not found upstream, the sand shiner (Notroois stramineus),
is common . Two other species, the rosefin shiner (Notroois ardens)
and the silver shin.er (Notropis photogeni •s), are rare in Hoover
tail water, although they are common. in the headwater streams above
the reservoir (Cavender and Crunkil ton 1974). The silver shiner was
also found in electroshocking samples in Barren Reservoir tailwater,
and the common shiner ( Notropi s cornutus) was ta..'ten from both Barren
101
Reservoir and Nclin Reservoir tailwaters, Kentucky (J. P. Carter
1968a). Edwards (1978) found the blacktai.l shiner (Notronis ve.nustus)
and Texas shiner (Notrop.is amabilis) in Canyon Dam tailvater, Texas.
Though there was no change in abundance of the Texas shiner, the
blacktail shiner '1."8.5 less abundant below the dam than in the stTeam
above the reservoir, presumably because of colder temperatures. in the
tailwater. Bauer (1976) identified the telescope shiner CNotropis
telesconus) in fish samples collected from Dale Hollow tailvater,
Tennessee.
Stonerollers
338. Habitat. This fish is most abundant in streams having
moderate or high gradients, well-defined gravel, rubble, or bedrock
riffles, and permanent flow. It is generally found on riffles or in
short, rocky pools where riffles and pools alternate in rapid succes-
sion. It seems generally tolerant of turbidity.
339. Reproduction. The stoneroller spawns earlier in the spring
than m0st other minnows. Spawning occurs on riffles where vater may be
up to 30 em deep. The e.ggs are deposited in shallow pits dug by the
males. Females remain in deeper vate;r near the spawning area, entering
the pits indi...,.idually or in small groups to depo.sit their eggs. Spawn-
ing occurs e.s one or more males press against the female,. The adhesive
eggs become lodged in the gravel and are abandoned before they hatch.
Eggs. hatch in 69-70 hours at 21°C. According to Smith (1935), nest
building in Illinois started in mid-April, when vater temperature vas
12°C, and spawning continued until early June, whe.n temperatures were
between 24 and 27°C .
340 . Food. The stoneroller lives in schools near the bottom.·
It feeds primarily on algae and detritus that it scrapes from rocks,
logs, and other submerged objects with the bladelike extension of its
lower jaw.
341. As.e a,"1d growth. Adult stonerollers are c.ommonly 75 to 165
mm long, and maximum length is about 200 mm. In Missouri, tbey com-
monly reach a length of about 35 to 60 mm ~J late August of the first
summer of life (Pflieger 1975). Maturity is reached in the second or
102
· ..
.. ~~ .
" . ...
_ .. ~ .. .. .
:;o_
··.~ .. .. .·~. .-
;•'' .
. ,
.•
third summer. Males grow more rapidly than females and attain a. much
larger size.
Stonerollers in tailwaters
342. The stoneroller is reported in a number of co·ld tailwaters.
It. vas the most abundant species co•llected in Beaver tail water,
Arkansas. It is also commonly found in the tailwaters of Bull Shoals
Reservoir and. Norftlr.k Reservoir in Arkansas (Brown et al. 1968; Bacon
e t &1. 1969; Hofflnan and Kilambi 1970). The stoneroller is abundant in
Apalachia tailwater, Tennessee (Hill 1978), and is also found in other
tailwaters of the Tennessee Valley system, whe·re it is used as forage
'
by game ·fish (Pfitz~r 1962). Stonero·llers vere also taken in electro-
fishing samples ~om Nolin tailvater, Kentucky (J. P. Carter l968a).
The shallow gravel-bedrock substrate and 14. 4 to 21. 7°C tempe.ratures
ba.ve favored the stoneroller in Hoover tailwater, Ohio. Large numbers
: of stonerollers spavn in the shallow riffles below the da.m and both
adults and young ar~ found in this tailwater throughout the year
(Cavender and Crunkilton 1974).
of< ··-~ ~ ..... ..; j il~·"-· , ~
··;· ·. ~');· :)·;.··-:Dace a in tail waters ., -~-.;~:;~:,~:·:~~l~:r·: .1
...
t ~
Membe,rs of seven genera of cyprinids are referred 'to by the ·:~,; 1:'
c011111l0tl name "dace." Only two genera, Phoxinus and Rhinichtbys, cQJD-
prising four species, have been reported in tailwaters.
344. Tbe speckled dace (Rhinichthys osculus) appears to do well
in some weste.rn coldwater tail water.s. It is abundant below Owyhee Dam .
and Antelope Reservoir, Oregon (Fortune and Thompson 1969) . This
species has survived below Blue Mesa Dam, Colorado, and has increased
in Fontenelle tailwater, Wyoming (Kinnear 1967; Mullan et al. 1976) • •..
. ·~ ·~
345. The longnose dace (Rhinichthys cata.ractae} has survived in ,
some cold tailwaters. It is commonly found below Owyhee Dam and has
survived below Graney Dam, Colorado (Weber 1959; Fortune and Thompson
1969). ·It.has disappeared from the warm tailwaters below four sJD&l.l
hydropower· dams ·on Michigan's Au Sable River (Richards 1976).
346. Two other species' of dace .bave been reported from cold
~-tailwaters. The southern redbel ly dac'e {Phoxinus erythrogaster) occurs
in pools below Norfork Dam, Arkansas (Brown et &1. 1968) • and the
103
•' , ....
,· .
...
-----;•--
·, ----·-~-_.··----·-~ ~:-.·· --~ .. ;. .. -~ .. -.... --~-:------:"'--.:..~
blacknose dace (Rhinichthvs a.tratulus) in the headwa.ter streams of Big
Walnut Creek, Ohio, and. occasionally downstream in the Hoover Dam
tailwater (Cavender and Crunkilton 1974).
Squaw1'ishes ·and chiselmouths in tailwaters · ...
347. Squawfishes and chiselmouths are found only in western North
America . The northern squawfish thrives in the warm (up to 26.7°C)
tailwaters below Cottage Grove Reservoir, Dorena Reservoir, and Fern
Ridge Reservoir, Oregon (Hutchison et al. 1966). This species also
·appears to do well in most co~d tailwaters. It, together with the
chiselmouth, is abundant below both Owyhee Dam and Antelope Reservoir
in Oregon (Fortune and Thompson 1969). Both the northern squaw'f'ish
and the chiselmouth are commonly creeled in a series of tailwaters on
the Snake River, Idaho, including Upper Salmon Falls, Lower Salmon
Falls, Bliss, and C. J. Strike (Irving and Cuplin 1956). A decrease in
tenperature and a resultant 6-to 8-week delay in spawning is believed
responsible for a reduction in northern squawfish numbers in a Montana
tailwater (May and Huston 1979).
348. The Colorado squawfish appears to have been affected more
. than the northern squaw'f'i sh by dam construction. The Colorado ,squawt'ish
has disappeared "from a cold tailwater in Wyoming (Mullan et ~· 1976)
and it is no longer fQund in a 105-km stretch of the Green River in
Utah and Colorado (Vanicek et al. 1970). Tempe-rature reductions and
alterations in normal flows may have eliminated it. It still. survives
furt~r. downstream, but the alteration of seasonal temperature patterns
since impoundment has reduced its growth rate {Vanicek a.nd Kramer
1969). Spawning migrations of Colorado squaw'f'ish in the Gunnison River
in Colorado have been disrupted by lowered temperatures and reduced
spring and summe r flows (Wiltzius 1978).
Cyprinids in Russian tailwaters
349. Dam construction ·and ope:ration in the So·viet l,Jnion have
affected many species of cyprinids. Historically, the bream vas the
pr·edominant s,ec ies of cypri nid in the Volga River in the vicinity of
the Kuibyshev Reservoir hydropcver dam (Diuzhikov 1961). Shortly after
dam closure, the bream, together with the bleak, white· bream, and roach
104
I ·.
...
(all cyprinids), were still nume-rous in the tailvater. However, un-
favorable reproductive conditions in the tailvater caused by water
temperature reductions, large diurnal water-level fluctuations, and a
severe decline in spring flood flows, soon resulted in a decrease in
abund.ance of all cyprinids { Sharonov 1963; Chikova 1968). Ide eggs,
laid in the shallows, ·were lost through desiccation due to fluctuation
in reservoir releases. Reduced temperatures in the tailvater delayed
the spawning of bream, white bream, and zope. Between 24 and 50 percent
of the females of t 'hese three species were found to be resorbing eggs
in 1.963 and 1964 (Eliseev and Chikova. 1968).
350. Decreased. spring flood flows below the Volgograd hydroelec-
tric facility have disrupted spawning conditions hundreds of kilometres
downstream in the Volga Delta on the Caspian Sea. Spring spawning
bream and carp have declined in abundance. However, the stabilizat:ion
of flows throughout the year below this dam have improved the repro-
ductive suc cess of the summer spawning white bream (Orlova and Popova
1976) ..
351. A reduction in mean ·water temperature of 4 to 5°C ha.'s f ·;.~ ~,':~·~·:· .
:·affected many cyprinid species in the taUvater bel·ov Mingesbaur
Hydroele.ctric Dam on the K·ura .River. Combined :f'yke net catches of
gudgeon, bleak, podust, khramulya, and barbel {all c:yprinids) hav·e
declined :from 73 percent before impoundment to only 40 percent after
impoundment. In f&.ct, the barbel and the bystryanka, have completely
disappeared. Thirty percent of the c.atch is nov composed of vobla,
bream, and carp which have moved downstream into the .tailvater from
the reservoir above. The al·~ered temperature regime has also shifted
the spawning activity of the shemia from early summer to autumn. 'I'h:..-5
shift in activity has not affected s,avning success, howev~r; large
numbers of shemia larvae and fry are still found in the tailvater
( Abdurakhmanov 1958) •
352. Reproduction of some cyprinid species has been disrupted by
t 'he large flow fluctuati~:ms occurring below Narvskaya Hydroelectric Dam
on the Narova Ri'ver. The spawning areas of the vimba have been sev:erely
altered because of flow fluctuations, while the fry and eggs of the
105
,. -
f,
I
1.
golden shiner (European) have been destroyed through the dewatering of
large sections of river bottom. Consequently, the numbers of both
species have declined (Barannikova 1962).
Catostomidae (Suckers)
353. The sucker family is largely restricted to North America.
Suckers e.re one of the dominant groups of large fishes in fresh water,
and in streams their total weight often exceeds that o-r all other fishes
combined. In nUDber of species and individuals, they rank second only
to the Cyprinidae. Each group of suckers has specific habitat prefer-
ences, and most are bottom dwellers· vi.th similar but not i .dentical
diets. All feed to some extent on larval and adult aquatic insects,
small mollusks, small c·rustaceans, worms, and ~lgae .. All suc,kers spa\ltl
in spring and none build a nest; eggs are scatte·reci in sui table 'habitat
and abandoned. Preferred habitat of the various species .ranges from
high, cold! mo\Ultain lakes and swift mountain stresms to warm, quiet
ponds and lakes.
354. Most suckers are captured during spring spawning runs by use
of gigs and snags; few are captured by book and line. Large numbers of
some species are taken by commercial fishermen. The flesh of suckers
has good flavor, but numerous sma11 bones detract from its value as
food. Small suckers are an important source of forage for game fishes.
355. Those catostomids that commonly occur in tailwaters vil1 be
discussed under three groups--buffaloes, suckers, and redhorse.
Buffaloes.
356. Habitat. The three buffalo species, bigmouth, smallmouth,
and black, have similar habitat requirements. They oc:cur primarily in
the deeper pools of large streams, natural lowland lakes, and man-made
impoundments. Buffaloes sometimes enter 'small streams to spawn, and
the young rne.y remain here during their first stmiDer of life. Their
distributional re.lation sugge,s.ts that the bigmoutb butt&J.o is 1110re
tolerant of high turbidity than, the other two, and that the black
buffa1o occurs most often in strong currents.
lo6
.·
...... .
: ·· ..
•,•.:
357. Reproduction. The spavning habits of buffaloes are not well
known. Buffaloes have been observed spawning in she.llow-water areas
of rivers and reservoirs with a water temperature range of 15.6 to
18.3°C, between April and June. The• adhesive ·eggs are broadcast into
the water, where they settle and adhere to the substrate-e.g., rocks
and t'l.ooded vegetation. Spawning occurs in water so shallow that the
backs of fish are often exposed. The eggs hatch in 9 to 10 days at a
water temperature of about 16. 7°C.
358. Food. Studies by McCamish (1967) and others revealed that
all ages of bigmouth buffalo feed principally on zooplank~on. The
large, terminal mouth and numerous slender gill rakers are efficient
devices for straining zooplankton from the water.
359. Zooplankton and attached algae were the principal foods
found in smallmouth buffalo stomachs (McCamish 1967). Tt ~s species is
primarily a bottom feeder, as indicated by the high frequency of insect
larvae, attached algae, and associated detritus and sand in the stom-
achs. The diet of the black buffalo is assumed to be similar to that
of the smal1.mouth buf.falo.
360. Age and growth. T'.1e bigmouth is the largest 'bu:ffalo species.
Adults are commonly 380 to 691 mm long and weigh 0.9 to 6.3 kg.
Weights of 13.6 kg are no-t uncommon. Small.mouth and black buffaloes
are somewhat smaller than the bigmoutb .
361. Buffaloes e.:re long-lived, many living more than 10 years.
Females grow larger than males. According to Scho·ffman (1943) the
average lengths and weights reached by the bigmouth buffalo in 'Reelfoot
Lake, Tennessee, through the first eight summers of life were as
follows:
.. -
107
. ~ .......
.......
Ase in summers Lens!:b 1 mm
2 335
3 386
4 424
5 455
6 528
7 597
8 668
362. Growth in weight increases progressively
eight summers, indica·ting that
a fast-growing period of life.
Buffaloes in taihraters
fish in their eighth
Weisht 1 k,s
0.7
1.0
1.1
1.4
2.4
3.4
6.2
dw-ing, the first
summe:r are still
363. Buffaloes inhabit primarily lakes or large rivers and gen-
erally are not important in tailwaters . In most instances vhere
buffaloes a~·e found in tailvaters, they have migrated into tbe area
from the downstream reservoir or river.
in
364 .::;, Smallmouth and bigm~uth buffaloes are cOllllon SUlllller i.nbabi-
tants of Levis and Clark Lake tailwaters in South Dakota and Nebraska.
Fish collected in June had already spavned, and it vas assumed that
their presence in the tailvater was related to feeding activity
(Walburg et al. 1971). The increase of smallmouth b\lffal.oes in Dale
Hollow tai'lwater, Tennessee, vas attributed to their migration upstream
from Cordell Hull Reservoir (Bauer 1976). Buffaloes are important in
t~e ~ler Rough River tailvater in Kentucky where they made up 9.3
percent of the fish catch by weight (Henley 1967). · This tailvater
differs from most because it is essentially a long pool created by a
mill dam 9.7 km downstream. These pondlike conditions closely dupli-
cate the preferred lentic habitat of the buffaloes.
365 . The shallow, fast water in most tail waters, coupled vi.th a
lack of recruitment, severely curtails or e·liminates buffalo popula-
tions in most tailwat~rs. Black buffaloes were i!liportant in an
Oklahoma tailvater shortly after impoundment. but were unable to sustain
108
; .
..
..
. :.·· : .......
.•
. · ..
themselves. This vas reflected by the rapid decline from 15 to 6 per-
cent of total catch v.t'thin 2 years (Hall 1949; Hall and Latta 1951).
366. The food of buffaloes in tailvaters has not been studied
extensively. Walburg ~~t al. (1971) found that bigmouth buffaloes from
Levis and Clark Lake tailvater fed almost exclusively on zooplankton in
the reservoir discharge, and smallmouth buffaloes fed on both zooplank-
ton in the discharge and on attached algae and b~Jozoans found in the
tailvater.
Suckers
367. A number of sucker species occur in tailvaters. Most com-
monly mentioned in the .literature are the northern hog sucker, spotted
sucker, river carpsucker, quillback carpsucker, white sucker, longnose
sucker, flannelmouth sucker, bluehead sucker, and largescale sucker.
The first four species ar7 generally eastern or midwestern Unit-ed
States in distribution, and the last four are extreme· northern or
western. The white sucker is more videly distributed, except in the
West and. South. Description of life history vill be limited to the
·northern hog sucker, spotted sucker, river and quillback ca.rpsuckers,···~ ...
vhi te sucke.r, longnos,e sucker, and largescale sucker. Description of
tail-water distribution includes all nine of the suckers mentioned
above plus several other less common species.
368. Habitat. The northern hog sucker is an inhabitant of
moderate-sized streams that have clean gravel or rock bottoms and
·permane~t flow. It is usually found on the stream bottom in riff les
or in pools with noticeable current. The heavy bony head, slender
tapering body, enlarged pectoral fins, and reduced svim o:adder permit
it to maintain a position in svift currents vith little erfort. The
northern hog sucker is nearly invisible on the stream bottom because
of its strongly mottled and barred coloration.
369. The spotted sucker lives in lakes, over flow ponds, sloughs,
oxbows, and clean s~uggish streams vith sandy, gravelly, or hard clay
bottoms vi thout silt. It seems intolerant to turbidity, pollutants,
and clay-silt bottoms .
109
370. Carpsuckers are common in large rivers, where they prefer
deep, quiet pools and backwaters with moderate or low gradients. The
river carpsucker prefers turbid waters with soft. bottcas, while the
closely related quillback is found in clearer waters with finm bottoms.
371. White sucker hebitat is extremely varied, since the species
occurs in both lakes and streams vi th low and high temperatures, lov
and high turbidities, and fast and slow currents. The vhite sucker has
fou."ld ma·n-made impoundments suitable, and bas become abundant in some.
This species is especially characteristic of head.vater streams.
372. The longnose sucker occurs in the cold, clear water of both
lakes and streams. Its occurrence in streams is usually related to
spawning activity.
373. Le.!-gescale suckers live in lakes a:nd in large .rivers. They
are often numerous in the veedy sho.reward areas of lakes, in backwaters,
and in stream mouths. This species and the longnose s·ucker are often
found together in the same general habitat.
374. Reproduction. The northern hog sucker spawns during spring
near the heads of gravelly riffles in water 8 to 13 em deep, when water
rl ...
·temperature reaches l5.6°C. Each female is attended by one or more·
males. The demersal, nonadhesive eggs are deposited in a depression
on the stream bottom and abandoned.
375. The spotted sucker spavn.s on riffles above large pools during
the spring when water temperature ranges between 15 and 18°C. The eggs
hatch in 7 to 12 days, depending on temperature.
376. Ca:rpsuckers are shallow-water, rand.ca. s ,pavners. They spawn
in the spring when water temperatures reach about 21°C. Eggs are
dispersed into the water column where they eventually settle to the
stream bottom and adhere to the substrate.
377. White suckers spawn in the early spring. Adults usually
migrate from lakes into gravelly st.reams when stream temperatures reach
l0°C, but they are also known to spawn on .lake margins, or· quiet areas
in the mouths of blocked streams and in tailwaters. Spawning sites 81"e
usually in shallow water vi th a gravel bottom, but they may also spawn
in rapids. No nest is built; eggs are scattered and adhere to the
110
._.,.-. . ·
:.';
..
··-.. '":•
sravel or dri!'t· downstream and adhere to substrate in quieter areas.
Eggs hatch in about 2 veeks, de,pending on temperature, and the young
remain near the hatching site for about 2 weeks before moving to quiet
areas along the stream bank or in a downstream lake . At this time,
t .hey are 12 to 17 mm long.
378. Longnose suckers spawn in tbe early spr:i ng in streams where
avatlable, but otherwise in shallow areas of lakes. They enter spawn-
ing streams as soon as the water temperature exceeds 5°C. The spawning
.run for this species reaches a peak several days bet"ore the run of
white suckers into the same stream. Spawning often takes place in
stream water 15.2 to 27.9 em deep, vith a current of 30 to 45 em/sec;
and. a bottom of gravel 5 to 10 em in diameter. No nest is built; the ·
adhesive, demersal eggs are laid in small numbers and adhere to the
gravel and substrate. Hatching and emergence of fry is similar to that
reported for the white sucker.
379. Largescale suckers spawn in spring, usually in deeper sandy
areas of streams vhere current is strong, but sometimes on gravelly or
·.sandy shoals in lake·s. '!'hey enter spawning streams when water· temper:..:-;~::
ature is 7.8 to 8.9°C and spawn a week or more later than the white
sucker~ in ~he same streams. Spawning activity and hatching and' emer-· p
gence of fry is similar to that reported for white-suckers.
380. ~ The northern hog sucker is an active feeder·, over-
turning rocks and stirring up the bottom as it forages for immature
aquatic insects and other bottom life vi th its fleshy, sucking lips.
381. The food of the s.potted sucker is said to consist mostly of
mollusks and insect larvae.
382. Carpsuckers brovse extensively on attached filamentous algae:
Other diet items include aquatic insects, worms, and mollusks.
383. White suckers have rather generalized food habits but subsist
mos-tly on immature aquatic insects.
384. The diet of longnose suckers consists almost enti rely of
algae, cbironomid larvae, amphipods, and other bottom organisms. Food
o·f young fish includes illmature aquatic insects, copepods, c.ladocerans,
and algae.
lll
·----------="-----'----....!....------'L...---
. • .. -
385. Th~ di~t of the largescal~ suck~r consists almost entirely
of bottom organisms such as aquatic insects, crustaceans, snails, and
alga~.
386. Age and grovth. According to Pflieger (1975), northern hog
suckers in Missouri streams reach a length of about 85 mm by the end of
their first year of life and average 165, 246, 300, and 330 mm in their
second through fifth years. Females grow mor~ ·rapidly than ~~s after.
the fifth year and attain a larger maximum size. Males mature at age
II and females at age III.
387. In Oklahoma. the spotted sucker attains a length of about
155 'IIDil in it.s first year and averages ·287, 338, 409, and 439 mm at the
end of succeeding years. Maturity is reached at 3 years of age, and
the maximum life span is about 5 years (Jackson 1957).
388. According to Pflieger (1975), river carps·uckers in Missouri
average 81 mm in length by the end of their first year of life and 165,
229, 312, and 348 IIDil in succeeding years. Maximum life span is at
l~ast 10 years. Average annual growth of the quillback carpsucker is
.slightly gr~ater than that of the river carpsucker. . .. . .
'. · · · 389. In Missouri, the white sucker averages 97 1IDD in length by
the end of its first year of life and 173, 229, and 297 mm in succeeding
years. Maximum length is about 508 mm. Fish mature when 3 or 4 years
old; males mature a year earlier than females.
390. According to Brown (1971), longnose suckers in Montana
average 76 mm by the end of the first year of lif~ and 140, 216, 267,
318·, apd 432 mm in succeeding years. The largest indi·vidual re.ported
for Montana was 564 mm long and weighed 2.2 kg. Fi·sh .mature at 4 or 5 ..... -·
years of age.
391. Grow-th of largescale suckers is generally slow . According
to Brown (1971), grovth in Montana averages 51 nun by the end of the
first yee.r of life and 89, 140, 190, and 254 mm in succeeding years.
Specimens es old as 11 years have been reported. This suck~r matures
when 4 or 5 years old .
112
..
......
. . . ~
·-·-~
....
Suckers in tail.waters
392. The effects of tailvaters on suckers have been varied, de-
pending on the type o.f tailvater and the species of sucker. Taken as
a group, suckers compose a significant segment of the fish population
in many t~lwaters.
393 . The northern hog sucker is abundant. in many eastern
coldwater tailvaters. Pierce (1969) found no change in the number s of
hog suck.ers below Swmnersville Dam in West Virginia following c~osure.
Hog suckers have remained extremely abundant in Chilhowee tailvater,
Norris tailvater, and Apalachia tailvater in the Tennessee Valley,
where young of the year are used as a food sourc e by game fish (Pfitzer
1962;. Hi ll 1978). The lover water temperatures (14.4-21.1°C), slightly
reduced turbidity, mixed gravel-bedrock substrate, and higher dissolved
oxygen level (always > 6. 0 mg/1) provide optimal conditions f o r pro-
ducin g large numbers of hog suckers below Hoover Dam, Ohio (Cavend~r
and Crunkilton 1974). Hog suckers apparently have 'been eliminated from
a cold tailwater in Arkansas . They vere numerous here in 1950 vhen the
·project 1laS comple ted but had disappeared by 1959 (Baker 1959; Brown :~ .;'"-:"·~~-··
1967). Reasons for the disappearance vere not specified. .'~----~:.,_,..._ -· _. ·
394. The spotted sucke r is also common in some eastern tailvaters.
It is one of the dominant species in Dale Hollow tallvater, Tennessee
(Bauer 1976). It i .s also foW1d in moderate abundance in the cold
tailwaters of Hoover Reservoir, Ohio, and East Lynn Lake, West Virginia
( Cave·nder and Crunk.il ton 1974; Goodno 1975). Occurrence in these
tailwaters is mos t likely due to transport of f i sh over the dam from
the reservoir above. Successful reproduction of spotted suckers occurs .
. primarily in Hoover -Reservoir. Young of the year escape over the dam
and are founci throughout-the length of lover Big Walnut Creek (Cavender
and Crunkilton 1974). Adult spotted suckers are the fifth most numerous
species lost ove·r the spillway of Little Grassy Lake in Illinois, com-
posing 8 percent of total fish numbers (Louder 1958).
395 . The river carpsucker occurs in both col.d and varm tailvaters.
It i s one· of t he major .r emaining native species found belov Canyon
Reservoir, Texas (White 1969). It is also abundant in Levis and Clark
113-
I
I
I
tailwaters on the South Dakota-Nebraska border (Walburg 1971). The
damming of Big Walnut Creek bas altered quillback distribution by
blocking upstream migration and increasing spring concentrations in the
tailwater {Cavender and Crunkilton 1974).
396. Ce.rpsuckers are among the most abundant fishes found below
dams in the Rio Grande, New Mexico. They remain abundant in spite of
the elimination of flows followi~g the irrigation season, which reduces
the river to a series of isolated pools (Huntington and Navarre 1957).
397. The food of the ::-iver carpsucker in Levis and Clark Lake
tailwate!' consisted primarily of zooplankton and algae (Walburg et al.
1971).
398. The white sucker has remained dominant in tailwaters below
dams on many rivers where it was abun.d.ant before impoundment. The
white sucker is adaptable to conditions in cold tailwaters which can
closely resemble headwater stream habitats. It is abundant below Hoover
. . .
Dam and is one of three dominant species in Rocky Gorge· tailwater,
Maryland ( Tsai 1972; Cavender an.d Crunldl ton 1974). In Twin Valley
. Lake tailwater, Wisconsin, the carrying capacity of the white sucker
increased threefold in the 3 years following impoundment · (Wirth et al.
1970). Even with a reduction of flows to only 11 percent of the
historic ave::-age., white suckers have remained numerous in cold Granby
tail water in Colorad.o (Weber 1959). They are also ab"..U'ldant . in the
tailwater below Holyoke Dam, Massachusetts (Jefferi~s 1974).
· .....
399. On some rivers, the construction of reservoirs has allowed
the white sucker to increase in numbers or become dominant in drainages
where it was pre\~ously of only minor importance. Increased a~undance
of the white sucker in Dale Hollow tailwaters, TeDDt!SSee, is attributed
to the deeper, more lentic habitat found in the lower tailwater, caused
by the downstreac impoundment of Cordell Hull Reservoir on the
Cumberland River (Bauer 1976).
400. !n the Taylor and Gunnison rivers in Colorado, the reduction
in temrera'ture and turbidity below some reservoirs has allowed the
white sucker to outcompete most other native suckEr species, e.g.,
flannelmouth and bluehead suckers (Mullan et al. 1976; Wiltzius 1978).
... • r
... ~ ....
The whit.e sucker is apparently able to reproduce in both of these reser-
voirs and te.ilwaters, which accounts !"or its dominance over the native
suckers in the Gunnison River drainage (Wiltzius 1978). Tailwater con-
ditions apparently aid growth, since the condition factor (weight in
relat,ion to length) of. white suckers increased in Blue Mesa tailwater
following impoundlcent (Kinnear 1967).
401. The longnose suc.ker has become abundant in the tailvaters of
two Colorado dams, and it has also displaced the nat:ive sucker species
(Mullan et a.l. 1976; Wiltzius 1978). The reduced temperature and
turbidity in these tailwaters, together with the longnose sucker's
ability to reproduce successfully, may give this s.pecies a competitive
advantage.
402. Longnose suckers also adapt well to reductions in flow below
dams. They have survived in flows amounting to only 11 percent of the
annual average (Weber 1959). Additionally, they remain in two Wyoming
tailwaters, in spite of a seasonal reduction of discharge from 24.5 to
0.04 m3/sec and 8.8 to 0.01 m3/sec, respectively {Wesche 1974).
The effects or reservoir construction and operation in· · .... ·-~.~-
·western rivers on the historically dominant flannelmoutb and bluehead
.suckers bave 'been mixed. The flannelmoutb ~;;ucker remains tbe most
.numerous native species below Glen Canyon Dam, Arizona, and the blue-
head sucker is still present in Granby tailwaters {We.ber 1959; Mul.lan
et al. 1976). Numbers of flannelmouth sucker have declined. in a
Wyoming tailwater because of reduced water temperatures {Mullan et al •
.. . 1976). Abundance of both the flannelmouth sucker and the b1uehead
sucker has decreased in a New Mexico t .ailwater because of reduced
temperatures and competition from trout (Mullan et a.l. 1976). However,
29 km downstream, wbe.re the river returns to 1 ts warmer, more turbid
c'ondi tion, the flannelmouth sucker still predominates (Graves and
Haines 1968, 1969).
404. The most serious reduction of bluebead and flannelmouth
suckers has occurred below two Colorado tailwaters W'here cold water
temperatures and reduced turbidity have allowed other species to ov.t-
compete them. The result has been the disappeara.nce of both species
1.15
'·· .. -
I r
I
I. o.
from one of the ·tailvaters and their general decline. in the· other
{Mullan et al. 1976; Wiltzius 1978).
405. The reduction of water temperatures in a Montana tailvater
-· · bas delayed reproduction 6 to 8 weeks for both. the largesc.ale and long-
nose suckers. Delay in spawning has decreased the abundance of large-
scale suckers in this cold tiailwater {May and. Huston 1979). N-itrogen
embolism 'below this site has caused sane mortality of largescale suckers.
Largescale suckers are extremely abundant below Dorena Dam, Fern Ridge
Reservoir, Lookout Point Dam, and Dex-ter Dam in Oregon, apparently
thriving in the 21 to 27°C temperatures commonly attained in these
warmvater tailwaters {Hutchison et al. 1966).
406. ·The effects of reservoir ope~ations on other less widely
distributed sucker species have also been mixed. Lowered water temper-
atures in a Wyoming tail water have eliminated the humpback suc-~er,
·wbi~e allowing the mountain sucker to stabilize or even increase its
population (Mullan et al. 1976).
407. The blue sucker of the Missouri River is abundant in the
._::_-spring and fall ·in' t:he warm Le_wis and Clar.k Lake tailwaters on the
·.South Dakota-Nebraska border . Here it feeds heavily on zooplankton
and algae and, COIIDDonly eats the bryozoans and aquatic insects that are·
also available (Walburg et al. 1971) .
. Red horse
408. Five species of redhorse are most often mentioned in litera-
ture on-:tailvater fish populations. They are the black, golden, silver, ....... · ..
s~_orthead, and river redhorse. Generally, little factual information
is available on their spawning habits, age, growth, or other life
history features.
409. Habitat. The various redhorses have slightly different
habitat requirements. They usual ly inhabit clear streams having per-
manent flov and clean gravelly or rocky bottoms. The black redhorse,
golden redhorse, and river red horse, are most abundant in st:reams of
medium size, whereas the shorthead redhorse and silver redhorse are
,most cOI!Dllon in larger rivers. The black redhorse is more abundant
than the golden redhorse in the cooler and swifter streams. Where, the
116
. ·~ ..
'·
•
tvo occur together, the black redhorse tends to predominate in short,
rocky pools with current; whereas, the golden redhorse is most abundant
in larger pools and backwaters without noticea'ble current .
410. Tbe river redhorse seems less tolerant of turbidity, sil ta-
tion, and. intermittent flow tba:n the other redhorse suckers. The
golden redhorse is the most tolerant of both turbidity and intermittent
flow, vhile ·the· silve·r redhorse avoids spring-fed streams having high
gradients and those that have excessively high turbidity . The short head
redhorse is the most adaptable in its habitat requirements.
411. Reproduction. Redhorses spawn in April or May when water
temperatures reach about 13.3°C . Spawning occurs on riffles in :water
15.2 to 61 em deep and over a bottom of small rubble mixed with lesser
amounts of small gravel and sand. No nest is buil t; eggs are scattered
over the gravel and abandoned. Spawning is completed on any given
riffle within about 4 days .
412. Food . Young-of-the-year redhorse feed in backwater areas
on algae and small crustaceans . Older fish shift their feeding activ-
. · · ities to riffles, where they forage for aquatic insect larvae and ····;;-.~·· ~·· ... : ·
othe·r small bott.om-dwelling invertebrate·s. The river redhorse has
molarlike tee·th that are an adaptation for the crushing of mo l lusk
shells. The· diet of this f i sh consists of mollusks, other inverte-
brates, and plant material.
413. Age and growth .. Accord ing to Pflieger (1975), shorthead
redhorse in Missouri streams reach a length of 107 mm at the end o f
their first year and in succeeding years lengths '!l.re 193, 264, 305,
an.d 335 mm. The maximum life span of most redhorse is 9 or more years,
except for the golden redhorse which usually does not live beyond 6 or
7 years.
414. Age and growth of the redhorses are simi l ar except t .bat
growth of the shorthead is more rapid than that of the golden and
black but slightly slaver than that of the silver. The river redhorse
usually grows slaver than the other species during the first few years
of life, but eventually it overtakes and. surpasses them; it also .has
a longer life span.
117
Redhorse in tailwaters
415 . The response ot: redhorse to tailvater condi'tions ia similar'
to that of other suckers. Redhorse have increased in a number of' cold
tailwater s in the Tennessee Valley (Pfitzer 1962). Redbo~se species
were also abundant below Buckhorn Dam, Kentucky, where they numerically
composed 49.8 percent of all fish present (Henley 1967). They were
abundant.-in an Arkansas tailwater shortly after dam closure in 1950,
but had disappeared by 1959 {Baker 1959; Brown et al. 1968). Cold
water temperatures apparently eliminated the redhorse from this
tail water.
416. The construction of Cordell Hull Reservoir has increased
water depth in t 'he downstream section of Dal e Hollow t ail water,
Tennessee. This alteration allowed the golden redhorse, a pool species,
to become more abundant {Bauer 1976). In the shallower tailvate,rs
below Hoover Re.servoir, Ohio, the golden redhorse is seldom seen
despite being the most abundant redhorse in the drainage. (Cavender and
Crunkilton 1974). Similarly, the golden redborse is of' only minor
.'~ili.portance in terms of numbers and biomass· in East Lynn Lake tailvaters
;· ... tn we"st vt~sinia · (Goodno 1975>. · '· ·~:. :.i-::1 ~: :~:<·-::_·.:·:~ · ,~:. ·. ;•:·.:>.'
417. The distribution of silver redhorse in Big Walnut Creek was
seriously influenced by construction of a reservoir . Although both
young and adults were abundant in the reservoir headwaters prior to
dam closure , they have subsequently disappeared. ~e presence of the
dam has prevented the return of the silver redhorse to its former
hz:?i t:S:t (Cavender and Crunkilton 197 4). Below Dale, Hollow Reservoir,
however, a popul ation of silver redhorse has become est ablished and
has been increasing (Bauer 1976).
418. Black redhorse are commo n in the t.ailwater below Hoover Dam
in Ohio. Many were observed in shallow pools below the dam in early
May, which suggests that they were attempting to spawn {Cavender and
Crunkilton 1974) .
. 419. Little has been reported on the ri'ver,·shorthead , e.nd gray
redborses . The gray redhorse has survived in the cold tailvaters below
Canyon Dam, Texas, and is one of the most numer ous native species
118
..
.,
..
.. .
··~ .
·· .. ~~-~· .· ...
:-...
·· ... -. •.
'·-
!'
remaining (White 1969). The river reaborse bas increased in the lover
tailvater of Dale Hollow Reservoir, Tennessee, since its inundation by
Cordell Hull Reservoir (Bauer 1976). The shorthead redhorse is abundant
in Levis and Clark Lake tailvate,r, South Dakota and Nebraska. Here it
feeds primarily o.n zooplankton from the reservoir discharge, but ·algae,
bryozoans, and aquatic insects are also C011Dftonly eaten (Walburg et al.
1971).
Ictaluridae (Catfishes)
420. The catfish family includes 37 species, all generally re-
stricted to 'North and South America. In the United States, they occur
naturally in larger rivers, lakes, and slow-moving waters eas't , of the
Continental Divide. Some of the larger species have been .widely int-ro-
duced outside their natural range and now occur throughout th~ United
States. Species commonly found in tailwaters are the channel catfish,
flat-bead catfish, and, to a lesser extent, bullheads; the blue catfish
:.
·· and the white catfish are important regionally. All a:r·e popular r~d
and game fishes. Lesser known species which also occur in tailvaters
'~:t ..... '.':"~ ·..,:_. ...
are collectively referred to'as "madtoms ." They are rarely seen "be-
cause of their small size and secretive habits. This discussion of
ictalurids includes the three general groups--bullheads, catfishes·,
and mad toms •
Bullheads
•' .. .. · ......
421. Habitat. The black, brown, and yellow bullheads· may occur ·
in tailvaters, but they are essentially quiet-water fishes found in
lakes, ponds, or sluggish streams. They occur in a variety of habitats,
but are· most abundant in areas with turbid water, a silt bottom, a:1d
D-' ~1 oticeable current O!" strong flow. Especially favorable babitats
are the permanent pools of small intermittent creeks and muddy oxbows
and backwaters of large streams. Black bu.1lheads usually inhabit the
lover sections of small-to medi.um-sized streams of low gradient,
.. ponds, backwaters of larger rivers, and silty, soft-bottomed areas of
lakes and impoundments. They do not inhabit the areas in which brawn
ll9
...
and yellow bullheads usually occur but seem to replace them if the
habitat deteriorates. Yellow bullheads seem to prefer clearer water.
422. ReProduction. The reproductive habits of' the bullheads are
similar. They spawn in late spring or early summer, vhen, water temper-
atures reach about 21°C, in saucer-shaped nests fanned out by one or
both parent fish. Nests are usually beneath some type of cover such
as logs or objects elevated above the stream bottom. One of the parents
remains continuously with the eggs until they hatch. f-1"innovs and
sunfi s .h e.re often observed near the nest, rushing in to eat eggs when-
. ev.er the opportunity arises. Eggs hatch in 6 to 9 _days. at 20.6 to
23.3°C. At hatching, the young are about 6 mm long; they remain in the
nest until about the seventh day. The young bullheads move about in a
compact school after leaving the nest, and continue to be accompanied
by one or both adults. The young are abandoned by the adults when
about 25 mm long but persist in schooling throughout the first summer
of life.
423. Food. Bullheads are truly omnivorous and feed primarily
from . the bottom on a variety of plant and animal material. Adults eat
immature aquatic insects, clams, snails, crustaceans, plant material,
leeches, and fish. Young up to 25 mm long feed almost exclusively on
small crustaceans. Older young feed on chironomid larvae, clu.doc.erans,
ostracods, ~phipods, and mayf~ies.
424. Age and growth. In Oklahoma vaters, the black bullhead
averages 94 mm in length by the end of its first year of life and is
about 170, 229, 274, 312, and 350 mm long at the end of succeeding
years (Houser and Collins 1962). Growth in various ha:bitats is highly
variable, however, being slowest in overpopulated ponds and streams
and fastest in ne:w impoundments. Bullheads· may grow to 250 mm duri.ng
the first year of life in new reservoirs, but may not reach this length
until ~he fifth or sixth year in an overpopulated stream. Maximum life
span is about 10 years, but few individuals live more t .han 5. Yellow
and brown bullheads attain slightly larger size than the black bullhead.
120
-•: -J-o• I ~·. : .•
·.
& ..... ·-
•.·
Bullheads in tailwaters
425. Bullheads may occur in tailwaters, but this habitat is
generally unsuitable because• of reduced turbidity and strong currents.
Bullheads found in tailwater•s are often produced in backwaters or in
the upstream reservoir and c.arri.ed through the dam into the tail water.
426. In some warm tailwat~rs, bullhea.ds coming from the reservoir
above are an important part of the fishery. A 1959 preimpoundment
rotenone survey of Barren River, Kentucky, estimated bullheads to be
0.5 percent of the river fish community; few were taken by anglers
(Carter 1969). In a 1968 creel survey at the Barren tailwater, it vas
estimated that 33.8 percent of the anglers' catch vas bullheads •. Fishing
success in the tailvater during 1968 was correlated with dam discharge;
fishing was good when disc·harge ·W'as high and. poor when it vas lov
(Charles and McLemore 1973). Good fishing success for bul.lheads during
periods of high flov and lov historical bullhead populations in the ·· ·
river, indicate that the bullheads were probably produced in the res.er-
voir and transported through the dam into the tailva.ter. The creel
:. censu s in the Barren tailvater from 1968 through 1971 sho~ed a steady.·,::.·~ •·' · . ~ ..
decline in the bullhead catch from 33.8 to 0.3 percent o .f the total.
.harvest (Charles and McLemore 1973). This decline .not only indicates
that the 'bull.head population vas unabl e to reproduce in the tailva.ter
environment, but also reveals a lack of further recruitme~:+. into the
tail water from the reservoir above.
427. Be,low Carlyle Dam, Illinois, bullheads made up 6.2 percent
of the 1968 catc h by anglers. The bullhead harvest ·was 0.38 fish/hour
in the reservoir compared with 0.08 fish/hour in the tailwater (Fritz
1969). These figures indicate a greater abundance of bullheads in the
reservoir. Apparently bullheads favor the reservoir habitat over the
florlng tailvater. Bullh.ead.s from Fern Rid!e Reservoir, Oregon, have
established a fishery in the -warm tailwater (Hutchison et al. 1966).
'Hall and Latta (1951) found that 8 percent of the fish in the stilling
basin. belov Wister Dem, Oklahoma, were black bullheads~ They believed
that the fish found in the warm tailwater, including the bullheads,
reflected the species composition of the reservoir above and not the
121
river downstream. The black bullhead is abundant in the Stillwater
Creek drainage in Oklahoma, but occurs infrequently in the Lake Carl
Blackwell tailvater. This is mo ;,t likely due to the strong currents
in tailvaters, which do not provide suitable bullhead habitat (Cross
1950).
428 . Bullheads are found in tailwaters vith vide temperature
ranges and lov dissolved oxygen concentrations. Electrofishing shoved
that black bullheads vere the most abundant fish and ranked third in
.. biomass in East Lynn tail water, \olest Virginia, where water temperatures
ranged from 5 to 25°C and averaged 16.6°C (Goodno 1975). Pierce (1969)
stated that bullheads became more abundant after construction of
Summersville Dam, West Virgj.nia, even though tailvater temperatures did
not exceed l5.6°C. Summers (1954) captured builheads by trap net below
Tenkiller Dam, Oklahoma, in vater of 12.2 to l7.8°C, svi,ft cur.rents,
and dissolved oxygen concentrations of less than 0.5 mg/1. Possible
increased production of bullheads in these reservoirs and their export
into the tailvaters may account ~or the large numbers of .bullheads ·
'.
· ,; . _ -pbserved. . ~': . ": : ~::~~ . : . ·::-~ .. · ~ ,: , .,_ '.f/~~;.{ _1"·=· ' ..
429. Only tvo papers reported food habits of bullheads in ·
tailwaters. Olson (1965) stated that bullheads in Navaj4:> ttt.ilvater,
Nev Mexico, ate a diet similar to that of rainbow trout, 'consisting of
dipterans, plecopterans, ephemeropterans, algae, and fish; only
gastropods (eaten by trout) vere excluded from the bullhead diet.
Brown bullheads below Holyoke Dam, Massachusetts, ate (by volume) 37.4
percent detritus, 35.3 percent algae, 11.8 percent pelecypods, 11
percent fish, 2.2 percent bryozoans, and 2.4 percent other items
(Jefferies 1974).
Catfish
430. Habitat. Four catfish species have been collected .from
tailwaters: channel catfish, flathead catfish, blue catfish, and
vhite catfish. The last tvo species resemble the channel catfish and
are regional in distribution. The white catfish is fo,und in Atlantic
coastal streams from Nev Jersey south to Florida, and the blue catfish
occurs only in the Missouri and Mississippi rive;s and their principal
122
.,
.. ,
'· . ' . . ; ... ~;
. '
tributaries. Tbil discuuion concerns only the cha.nnel catfish. The
flathe•d catfish may occ·ur in ·tailvaters, but is 11 ttle I!1entioned. in
tailwater literature.
431. The channel catfish is found in a variety of habitats but 11
most common. in large stream.s having low or moderate gradients. Though
c·hannel catfish prefer currents, excessive current or insuft'ic.ient water·
depth limits the.ir distribution. Adults are usually found in deep-water
pools or near submerged logs and other cover. The young are commonly
found in riffles or the shallower parts of pools. Adults are most
active at night, when they move into shallow water to feed.
432. Reproduction. The channel catfish spawns in late spring or
summer when water temperatures are between 24.0 and 29.4°C. Catfish
spawn in nests selected by the male. Nest sites are natural cavities
under submerged logs or debris, animal burrows, or undercut stream
banks. The eggs hatch in about a week and the fry remain in the nest
for 7 or 8 more days. The male guards the nest until the fry leave.
Because of predation, the survival of catfish during their first-summer
•; I
. of life is· usually greater in turbid than in clear ponds or streams. ..-. ·
433. Food. Channel catfish feed mostly on the bottom and locate
food primarily by taste. Bailey and Harrison (1948), who conducted
studies on the food habits of channel catfish in the Des Haines River,
Iowa, found that fish less than 100 mm long fed almost entirely on
small insects. Larger catfish had a more varied diet, including fish,
insects, crayfish, mollusks, and plant material.
434. Age and growth. In the Salt River in Missouri, the channel
catfish averages 65 mm in length at the end of its first year o~ life
and is about 135, 206, 259, 297, 340, and 399 rnm long at the end of
succeeding years (Purkett 1958a}. Studies by Barnickel and Starrett
(1951) in the-Missouri-Illinois section of the Mississippi River showed
that channel catfish mature when ' 4 or 5 years old at a length of 305 to
381 mm. Adults were commonly 305 to 815 aun long and weighed 0.4 to
6.8 kg. Life span is apparently dependent on growth rate. Slow-graving
fish in Canada may live longer than 20 years; whereas, fast-grcwing fish
from the southern United States may not live longer than 6 or 7 years,
123
...
I
~~
I
I
I
i; r
I
Catfish in tailvaters
435. Channel catfish ere important game fish in ·some t&ilvaters,
particularly in the southeastern United States. Change.s in stream
habitat caused by dam construction have had varied effects' on channel
catfish. They are often abundant in the warm tailwaters of. turbid
main-stem or tributary rivers but are uncommon. or absent in clear, cold
tail waters.
436. Channel catfish disappeared from the angler catch in a
M1ssouri reservoir because of coldwater discharge (4.4-15.6°C) from an
upstream reservoir {Hanson 1969). Below an Arizona dam, channel
catfish were second in importance to rainbow trout until the vater
cooled from 14. 8°C in 1967 to 10. 4°C in 1971 and. 1972. The cooling
trend caused channel catfish to leave the tailvater (Mullan et al.
1976).
437. Channel catfish abundance below a Kentucky reservoir appar-
ently decreased after dam construction ( Carte·r 1969). Water is re-
,leased from the hypolimnion to maintain a tail~ter trout fishery .
C~el catfish c~posed 35.4 percent of the ~ngl~rs;' catch in the
tailwater area before impoillldment 'in 1959, but never more than 2 per-
cent after impouncbne.nt (Carter 1969; Charles and McLemore 1973). The
change .. from hypolimnetic releases in 1968 and 1,969 to epilimnetic
releases in 1970 and 1971 did not noticeably affect the channel catfish
catch. Both release regimes resulted in water temperatures below those
o.f th!Ot.historical monthly average for··tbe Barren River (Carter.l969).
438 .. Do'lll1stream from a cold tailwater, as local conditions
moderate the dam discharge, catfish populations may inc·rease . Graves
and Haines (1969) stated t hat channei catfish were the main game fish
29.0 km below a New Mexico dam vhere turbidity and water temperature
had increased. Further upstream in the tail water, trout predomi,nated.
439. Turbid main-stem teilwaters and tributar y warmwater
tailwaters often concentrate catfish and e reate a fishery. Cross (1950)
believed that char~el catfish below Lake Carl Blackwell, Oklahoma,
had escaped from the reservoir and remained in the tailwater because
food was abundant and flows were stabilized. In June and July, an
124
-··.-.. :.-...·-.:-f·
upstream migration of channel catfish in Stillwater Creek resulted in
a large concentrati,on in the Blackwell tailwater. Channel catfish vere
also most abundant in Levis and Clark tail water, South Dakota, during
the SUIIIDer ('Walburg 1971). Channel catfish concentrate and provide a
fishery below Lock and De.m Number 12 on the Mississippi River in Iowa
(Gengerke 1978). This species is second in biomass and fi .fth in abun-
dance in East Lynn Lake taih;ater, West Virginia. ( Goodno 1975). A
comparison of the fish population in t .he stilling basin area before
and after· closure of the warmwater Wister Dam, Oklahoma, showed a
reduction in the channel catfish population from 34 percent of the
total numbers of fish to 11 percent (Hall and Latta 1951). The reduc-
tion reflected the change of a community associated vith a river to
one 'IDIOre c0111Donly associat.ed vi th a reservoir.
440. Little information. is available on th.e fooC! and growth of
~hannel catfish .found in tailwaters. In Levis and Clurk tailwater,
they ate fish, crayfish, and aquatic insects . In April and May, when
Hexagenia was abundant. in the tailwater, it was a major food item, but ...
as abundance of He.xagenia declined in the stDIIDer, catfish ate mo're · fish ··-~.
(Walburg 1971). ··Catfish in Dale Hollow tailvater, Tennessee, ate pri-•·
marily dipterans (Littj,e 1967}. · Channel catfish grew faster in Levis
and Clark Lake than i.u the tailwater (Walburg 1971).
Mad toms
441. Habitat . Had toms inhabit clear to moderately turbid streams
having permanent flow and low or moderate gradients. Some species are
also found in the shallows of lakes and their outlets. 'rhey generally
occur on riffles over a gravelly or rocky bottom. Some species may
·· also be found over sandy bottoms in areas vi th fast current, and
others, such as the brindledmadtom,in pools below riffles associated
vith organic debris such as roots, leaves, tvigs, and logs. Species
vary in their tolerance of current and turbidity. Madtoms a:re most
active at night, often hiding by day beneath large rocks or other
cover.
442. Reproduction. t;fadtoms spawn .from late spring into the sum-
mer. Peak spavning occurs when water temperatures reach 25 .6 to 27.8°G.
125
----......_. ______ _
..
Eggs are deposited as a compact cluster in a shallow depression exca-
vated beneath a flat rock or other forms of protection such as tin
cans, boards, or crockery. Nests are guarded by one of the parent
fish. 1~e,dy hatched young are about 10 mm long.
443. Food. Madtoms are active at night, foraging over riffles
and shal low pools. They feed primarily on insect larvae and small
crustaceans that live on the bottom. Occasional small fish are also
eaten.
444. Age and growth. Little information is available on gr-:>vth
of madtoms. Carlson {1966), who studied the stonecat in the V~rmill ~~n
River in South Dakota, found that they averaged 79 mm at the end of the
first year of life and 99, 114, and 137 mm by the end of succeeding
years. The largest specimen was 193 mm long and in its seventh year.
445. Other species of madtom are smaller than the stonecat and
their total length at the end of their first year ranges from 36 to
64 mm. Adults of most species are 51 to 102 mm long and maximum length
is about 127 mm.· Many mature in their second s-ummer and few live longer
than 3 years.
:)' MadtO..s in tail waters
446. There are few reports on madtoms in t ail waters. Carter
{1969) found the brindled madtom in the Barren tailwater, Kentucky,
in 1964 and 1965. Four species of madtoms--the slender, brindled~
freckled, and an undescribed species-were collected. in the Barren
River during a preimpoundment survey in 1959. In the Owyhee River,
Oregon, tadpole madtoms were commonly found in both the tailvater
belov Owyhee Dam and in the reservoir above {F"ortune and Thompson
1969). Stonecats vere collected below four impoundments on the Au
Sable Rive:-, Michigan, in the 1920's, but none ·were collected in a
1972 survey {Richards 1976).
Percichthyidae (Temperate Basses)
-'··
447. These basses include several freshwater and marine genera.
The white bass and the less common yellow bass 'bot'h occur naturally
126
.. · , . . . ".•.
.. . . •
J
in the Miss.iss.ippi River drainage. The· striped bass was introduced
into many reservoirs during the past 20 years .from anadromous stocks
native to coastal rivers and estuaries in Virginia, North Carolina, and
South Carolina. These plantings have been successful in some states,
&ad. striped bass are nov relative·ly common in some river-reservoir
systems. Examples of states vith successful striped bass fisheries in
both reservoirs and tailvaters are Oklahoma and Tennessee. Reproduction
of introduced striped bass has been limited, and the maintenance of
fishable stocks is often dependent on annual plantings of hatchery-
produced fish. The life history discussion of temperate basses is
lici ted to the white bass; the tail water discussion incl udes both ·•··
white bass and striped bass.
White bass
448. Habitat. White bass inhabit the· deeper pools of streams
and the open waters of lakes and reservoirs. During the spring spavn-
ing migrati.ons, large· numbers. enter tributary streams and are the. basis
for an important seasonal fishery. The white bass ten ds to avoid
.,.,.. . ' . '·,,
.. .. vaters that are continuously turbid and. is most often found over a tina
sand, gravel, or rocky bottom. It bas 'been introduced into many lakes ·.
and reservoirs throughout the United States.
449. Reproduction. The white bass spawns in earl y spring and
spawning is usually preceded by tht~ migration of mature adults into
tributary streams. The prespavning schools are composed of only one
sex. · Males move onto the spavniog grounds about a mont.h before the .
females. The spavning ,Period throughout their range is from April
~ ..
through June, when water temperature is about 15.6°C. Spavning occurs
in midvater or near the surface, over a gravelly o.r rocky bottom,
often in a current, and vi thout preparation of a nest. Spawning is
generally completed at any given locality over a period of 5 to 1 0
days; there is no parental care of eggs or young. The eggs settle.to
·the bottom, where they hatch in about 2 days. Ne-wly ha.tched larv.ae
are about 3 mm long.
450. Food. White bass usually feed in schools, appea·ring in
·large .numbers where food is abundant and moving on vhe.n the supply is
127
---·-----...... ---~~ ----... ··---·-··-·-----·-.. _.,. ___ , lilt •. ..,.,::!);~
,·
...
...
exhausted. Most feed near the water surface in early morning and late
evening, vhere they pursue forage fish, small crustaceans, and the
emerging stages of aquatic insects. Zooplankton and aquatic insects
s.re the most important diet items for young vhite bass. The diet of
adults is largely composed of fish; however, zooplankton and insects
are also important.
451. A~e and growth. Growth of the vhite bass is rapid; the life
... span is seldom more than 4 years in southern vaters, but may be 7 or 8
years in northern vaters. In Lake Wappapello, Missouri, tbis fi.sh
reached a length of about 185 mm its first year and averaged 302, 338,
and 358 mm by the end of succeeding years (Patriarche 19-53). Fev
vhi te bass attain a length and veight of more than. 445 mm and 1. 2 kg ..
Temuerate basses in tailvaters
452. The vhi te bass is a.n i.nportant. sport fish in many tailvater·s,
especially during the spring. In the varm tailvaters of Clearwater
Lake, Missouri, it made up 3.9 percent of the anglers' catch in 1961
and 14.1 percent in 1964 (Fry 1965; Hanson 1965). It composed 8 per-
cent ~r the anglers' catch belov Pomme de Terre Reservoir, Missouri,
during 1965-74 (Hanson 1977).
453. In tbe Tennessee Valley, white bass support important spring
fisheries in cold tailvaters, which are primarily the result of spring
migrations upstream from reservoirs (Pritzer 1962). The fish is a
·particularly importan·t game species belov the main-stem reservoirs;
for example, in Watts Bar tailvater it canposed 18.8 percent of the
anglers' catch in 1953 (Miller and Chance 1954). Large num:bers of
vhite bass have also been observed migrating upstream out of Watts Bar
Reservoir into Norris Dam tailvater (Escbneyer and Mange! 1945).
454. In Dale Hol1ov tailvater, Tennessee, vhite bass became
abundant in the lover tailvater after the filling of Cordell Hull
Reservoir (Bauer 1976). White bass are also important in the fishery
belov Tenkiller Dam, Oklahoma, vhere they composed 8 percent of tbe
catch immediately belcv the dam and 43 percent .at a point 12.8 km
dovnstream (Deppert 1978).
128
J
;• ..
. ·. • ... ~-
·-: .
......
-:., ...
455. Lake Taneycomo tailvater, Missouri, is influenced by the
presence of Table Rock Reservoir upstream and Bull Shoals Reservoir
downstream. Increased power production at the deep-release Table Rock
Dam has converted Lake Taneycomo tailwater fr0m a varmvater to a
coldwater tailvater, making conditions unfavorable for varmwater game
fish. The magnitude of spring migration of vhite bass into Lake
Taneycomo tailwater from Bull Shoals Reservoir, hovever, is most heavily
influenced by the level of Bull Shoals Reservoir, vhich inundates Lake
Taneycomo tailvater. Maximum spring migration of vhite bass intq the
tailwater occurred vhen Bull Shoals Reservoir vas betveen 0.6 and 3.0 m
belov paver pool. Above or belov these levels the migration rate
declined proportionately (Fry 1965; Hanson 1969).
456. The food and reproductive habits of vhite bass in tailvaters
are not vell .known. Of 165 stomachs of immature vhite bass collected.
from Norri.s tailva.ter, Tennessee, in the vinter of 1942-43, 140 vere
empty (Eschmeyer 1944). White bass in Levis and Clark tailvaters,
. :
-:·. ..
.. ..:
... • .. ·. South Dakota, fed .. ~:n zooplankton. in the spring and tall, and pre~,;-.. ·.;·.;~~.iif;~ .. :>:
:·~ · dominantly fish in SUlllllier (Walburg et al. 1971). Litt.le reproductive ·· ....
~ • 4J, :
.. ·
success· was noted in either of these tailvaters · (Eschmey~; ~d ~ges -~
• ~1 '. '" ,. ·w •
1945; Walburg et al. 1971).
457. Striped bass have been stocked in a number of reservoirs
and tailva.ters in an effort to control large gizzard shad populations
and to enhance the sport fishery; hovever, they have been found to
compete vi th trout in tail waters. Belov Davis Dam, ~izona, 24 trout
<?00 to 230 m:m long vere found in 20 striped bass stomac~s examined
(Arizona Game and Fish Department 1972). Additionally, food studies
. on striped bass in Tenkiller tailvater, Oklahoma, shoved that rainbov . .
trout composed 40 percent by number of the food items eaten by striped
bass during the first veek after the trout vere stocked. Gizzard shad
vas the prima1·y striped bass food in this tailvater, accounting for
56 percent of the total number of food items during the first veek
after trout stocking and 75 percent at other times (Deppert 1978).
Similar results vere noted in Keystone Dam tailvaters, Oklahoma, vhere
gizzard shad made up 85 percent of the food eaten (Combs 1979).
129
... ..
.. : ... ·• '• ":~.
. ,,
~-
.C!:
Centrarchidae (Sunfishes)
458. Fishes of this family are found in nearly all types of waters,
and most are highly sought by sport fishermen. Their habi.ts and li'fe
history are similar, differing only in detail. Ce~trarchids migrate
little; oost remain in the sa."l!e stretch of stream .or shoreline through-
out life. Feeding is by sight., and feeding activity peaks in early
morning and late evening, accompanied by movement into. shallow water.
All centrarchids construct nests for spawning, but only males partici-
pate in this activity. They guard the eggs after they are deposited
and remain until fry leave the nest. The centrarchids are discussed
under three general groups--black basses, "true sunfi-shes," and
crappies.
Bla·ck basses
459. Three black bass species are commonly found in tailwaters--
tbe smallmouth bass, spotted or Kentucky bass, and largemouth bass.
460. Habitat. Smallmouth bass prefer clear; cool, permane·nt-
f'loving streams vi th good gradient ( 1. 3 to 3. 8 m/km). Preferred SUIIIIIIer .-...
vater .'temperature is about 21 °C. The fish generally occur, over a. ··:, : l -... ,·: • ·
silt-free rock or gravel bottom, near riffles, but not in the main
current. Adults are most abundant near cover in the form of boulders,
roots, or sunken trees. In large rivers vi tb navigation dams., they are
usually restricted to the rocky shoals below dams, whe~e streamlike
conditions still prevail. The smallmouth normally limits its. acti vi-
t .ies to a single stream pool, but occasionally its home range includes
several pools as much as 0.8 km apart.
461. Spotted bass inhabit flowing waters that are warmer and
slightly more turbid than those favored by smallmouth bass. Preferred
. summer temperature is about 24 °C. 'The habits of the spot ted bass are
similar to those of the smallmouth, except that ·the spotted, bass is
more migratory.
462. The largemouth bass is more widely distributed than the
other basses and is the most abundant bass species in standing-water
habitats. Its preferred summer temperature is about 27°C. It is
130
'· , ....
commonly :round in lowland lakes, reservoirs, slow-flowing streams, and
backwaters of large rivers. It is intolerant of exce;sive turbidity,
and in streams with continuous strong flow it is rep:d.ced by one of the
other basses. The . a.rgemouth displays more seasonal movement than
either the smallmouth or spotted bass.
463. Reproduct.ion. The smallmouth bass begins nesting in the
spring ~hen the water temperature exceeds l5.6°C. Nesting activity
usual.ly peaks in late spring, but sometimes continues well into early
summer. Renesting occurs if early nests are unsuccessful because of
high water or low temperatures, and may occur even if the first nests
are successful. Nests are in quiet water near shore or downstream from
a boulder or other obstruction that breaks the force of the current.
Water depth rarely exceeds. 1m over the nest. Smallmouth bass eggs are
golden yellow and about 2. 5 .mrn in diameter. They are distinguished
from those of the spotted bass and largemouth bass by' their larger size.
Eggs hatch in 2 or 3 days and fry rel!lain on the gravel for about 6 days
before leaving the· nest.
464. Spotted bass generally begin spawning several .days later.: b ·.•• •• •
than smallmouth bass in the same stream. Nest-s are similar to those of_~."-.~·
the smallmouth bass, and the development of eggs and fry is similar at ·
the same temperature. Fry of the spotted bass disperse from the nest
8 or 9 days after spawning if the water temperature is above 20°C. ·
465. The largemouth bass begins spawning in the spring when water
temperature reaches about l5.6°C and continues into late spring. Nests
are constructed on almost any type of firm, silt-free bottom. Water
...... depth over nests may vary from 0. 3 m or less to 4. 6 m or more, being
.deepest in the clear waters ·)f large impoundmen-ts. Nests are n.ever
constructed where there is current or wave action. In streams, nests
are located in the deeper and quieter parts of pools or in adjacent
sloughs. Eggs are about the size of spotted bass eggs and are much
·smaller than thos·e of the sm.'lllmouth. They hatch in 3 or 4 days and
fry leave the nest as a school when about 10 days old. Schools break
up 26 to 31 days after hatching, when the young bass are slightly over
25 mm long. The male largemouth is a more attentive parent than any o:r
131
,. ,.
:,
:· . -
the other sunfishes, remaining with the schooling young for several
weeks after they leave the nest.
466. Food. Midge larvae and zooplankton are the first foods of
smallmouth bass. fry. According to Pflieger (1975), fry less than 25 mm
long eat small fish, and fish .remain an important part of their diet
throughout life. Crayfish and fish occur in about equal amounts in the
diet of adult bass. Insects are taken frequently but are of only minor .. ·
... importance ..
467. Immature stages of aquatic insects are the principal diet of
spotted bass of all sizes. Insects are supplemented with small crusta-
.. · c~ans in bass less than 75 mm·long, and with crayfish and fish 'in larger
bass (Smith and Page 1969).
468. The first 'rood of young largemouth bass consists mostly of
zooplankters, but these are supplemented by insects and their larvae as
the young bass increase in size (Pflieger 1975). Adults feed princi-
pally on fish,.crayfish, and large insects, along with an occasional
.... frog, mouse, or ~ost any other animal that . swims or falls into the :.7 ·.
·_':.water. :In 'large re•se·rvoirs, the largemouth bass depends heavilY. on
' •• ,· • • • ; ' t " I
gizzard shad as foo~, and there is a definite relation between the
trends in abundance of the largemouth a .nd those of its principal. prey
species.
469. Age and growth. In Missouri streams. the smallmouth bass
averages 90 mm long when 1 year old, and attains lengths of about 170,
244, 290, 343, and 371 mm in succeeding years {Purkett 1 958b). As is
coDJDon in fishe.s, growth is more rapid in larger streams than in
headwater creeks. A Missouri smallmouth bass weighs. about 225 g at a
length of 254 mm, and about 625 g at 356 mm . Smallmouth bass seldom
exceed a length of 560 mm or a weight of 2.5 kg. Missouri smallmout'h
bass bec.ome mature during their third or fourth summer of li.fe and .
some live 10 or 12 years.
470. Growth of spotted bass is slightly faster than that of the
smallmouth for the first 4 years of life but is slower thereafter. In
Missouri streams, lengths attained are about 85 mm the .first year and
about 183, 254, 292, 322, and 353 rmn in succeeding years (Purkett
132
..
1958a). Growth appears to be more rapid in reservoirs than in streams.
Most fish are mature when 3 or 4 years old. Few spotted bass live
longer than 6 years or attain a weight much greater than 1.4 kg.
471. Growth of the largemouth bass is extremely variable, depend-
ing on local conditions. In Lake Wappapello, Misso·ur.i, a length ot
about 135 mm is attained the first year and lengths of 277, 338, 409,
460, and 498 mm are reached in succeeding years (Patriarche 1953).
Growth rates are similar or faster in new, well-managed ponds, but much
slower in highly turbid or overpopulated ponds, which may contain bass
4 years old or older that are still less than 254 mm long. Fish mature
between the ages of II and IV, depending on growth rate. Under average
conditions a 305-mm bass weighs about 340 g and a 560-mm bass about
2. 7 kg. Individuals weighing more than 3.6 kg are not uncommon. Few
.largemouth bass live beyond 12 years.
Black basses in tailvaters
472 . Black basses· are important game fish in. rive.rs and reservoirs
in many areas of the United States. They occur in tailvaters if vater
.. --:·.r·
temperatures are suitable and cover is adequate. Black bass populations
have be.en reduced below many hypolimnetic release dams constructed on
varmwater streams because of low water temperatures, strong currents,
and lack of instream cover.
473. The smallmouth bass fishery below Hoover Dam, Ohio, was lost
due to hypolimnetic water discharge from the dam (Cavender and
Crunkil ton 1974) • Pierce ( 1969) showed a reduction in smallmouth
populations from 7. 24 to 4. 72 kg/ha in the Summersville tailvate '!*,
West Virginia, based on preimpoundment and postimpoundment electrc-
fishing studies. The maximum temperature in Summersvill e tailwater is
15.6°C, which is below the optimal range for smallmouth bass. l)endy
and Stroud ( 1949) belie.ved that low water temperatures and low dis-
solved oxygen following construction of Fontana Dam, North Carolina,
adversely affected smallmouth bass for many miles downstream in the
Little Tennessee River . The coldwater discharge from Table Rock
Reservoir, Missouri, caused the loss of smallmouth and spotted bass
downstream in Lake Taneycomo (Fry and Hanson 1968).
133
474. Cold tailvaters below two dams in Kentucky support fever
black basses than occurred in the natural river before i~undment.
Black basses ve.re estimated to be 47,9 and 19.1 percent ?f the angler
catch in a 1959 creel survey from these tvo rivers (J. P. Carter 1968a).
In 1968-71, after dam construction, black basses. composed only 0.1 to
2.6 percent of the angler catch (Charles and McLemore 1973). Apparently
the tailwater habitat differed from the original varmvater stream habi-
tat and did not provide the conditions necessary to sustain t.he bass
.fishery.
475. Sroallmouth bass vere common in angler catches in the
tailvater below Cherokee Dam, Tennessee, .for the first 8 years after
impoundment. The fishery changed thereafter, and anglers had to fish
32 to 40 km do'Wt'lstream to catch smallmouth bass (Pfit:z.er 1962). Low
vater temperatures apperently reduc·ed bass reproduction and numbers i ·n
the upper 32 km of the tailvater.
476. Eschmeyer and Manges . (1945) shoved that the condition, factor
~ •. of'larg'em~·uth bass declined f~om aut~· 1942 'to ·autumn 1943 in a
··Tenne.ssee taii~at'e;~ They believed the fish ve;e experiencing lugh ..
::: ... • ••• ·.: ... ; J,. -· • • .. • • 'oo; -•• ~; • \ • .. .--:;i~.,.. ... ;.'
natural mortality 'due to the harsh habitat in this 'cold tailvater."·•'-'• ~ ··· · •J
477. Some varm and cool tailvaters sustain black bass populations
when water temperatures and cover are adequate. Many young-of-the-year
smallmouth bass were captured by seine below a low-head dam on the
Maquok:ta River, Iova. The large concentrations: of fish in this
tailvater were believed to be a res-ult of high oxyge.n levels, blockage ··.. ,.
of upstream movement, and habitat diversity (Paragamian 1979).
Hutchison et al. (1966) found low to moderate smallmouth bass abundance
below Cottage Grove Dam and Dorena Dam, Oregon. These flood control
dams have caused an increase in water temperature in the tailvaters and
have made them more sui table for smallmouth bas·s and le.ss sui table for
trout and salmon. And.revs et al. (1974) compared the catch of
largemouth bass in the river above and below an Ok1ahoma reservoir.
Historically, largemouth bass vere abundant in the deep pools of the
do'Wt'lstre&."D section where flows were more stable. After impoundment,
92 percent of the largemouth bass were ca.ught in the rive-r above the
134
~-·
~ ..
... • ··· ... · ···•· .,
.-··.
........
reeervoir, and they provided 35 pereent or the eet!mated eateh or all
tilh epeeie1. Cool water dileharge and. tluetuating tlovs belov this
main-stem hydropower dam apparently reduced habitat suitability for
largemouth bass in the tail water .
478. Food of largemouth and smallmouth bass f'rom Holyoke Dam
tailwater, Massachusetts, was studied in 1972 (Jefferies 1974). The
frequency of occurrence. of fish, insects, and crayfish in largemouth
bass stomachs was 88.9, 16.7, and 7.8 percent. Fish (spottail shiners)
made up 93.4 percent and crayfish 5.3 percent of total food volume.
The largemouth bass selected spottail shiners over Alosa s:pp.
Smallmouth bass stomachs contained fish, insects, c.rustaceans, and
pelecypods •.. Fish made up 45 percent of the stomach contents, crusta-. ..
ceans 35 percent, and pelecypods 20 percent. In largem.outb bass
·:·collected belov Norris Dam, Tennessee, 42 of 53 stomachs examined vere
empty. Apparently the cold tailvater did not provide good bass habitat
since the fish exhibited no growth (Eschmeyer 1944, Eschmeyer and
Manges 1945).
479. Reproduction of black basses in tailwaters is not vell docu-
mented. There is no documented reproduction of smallmouth bass in
South Holston tailwater, Tennessee. No juvenile bass were captured in
this tailvater and many adult females from a November 1953 collection
had resorbed. their eggs (Pfitzer 1962). Young-of-the-year largemouth
bass were the most abundant centrarchid in collections taken in 1965
bel.ov Beaver Dam, Arkansas. However, it is not knovn whether these
fish were produced in the tailwater or had moved out of the reservoir
above. In 1966, no largemouth bass adults or juveniles were captured
in the tailwater (Brown 1967).
480. Generally, cold tailwate.rs do aot provide good bass habitat.
Limited bass fisheries have developed below some dams, but fish harve$t
usually 'remains lov. Successful bass fisheries are usually found in
warm tailwaters with backwaters or other sheltered areas.
True sunfishes
481. The most common o f the "true sunfishes" (a term applied here
to the Lepomis sp. of the family Centrarchidae) occurring in tailwaters
135
..•
...
&re the bluegill, gree.n sunfish,. and longear sunfish. Also included
in thi.s section is the rock bass. Other true sunt'ishes may be locally
abundant in tailvaters, but their life histories are generally 1Sim.ilar
to those described.
482. Habitat.. The bluegill is common in the deeper pools and
backwaters of' streams, and in lakes, ponds, and reservoirs. It is
intolerant of continuous high turbidity and siltation and thrives best
in warm, quiet-wat.er areas vi th some aquatic vegetati.on.
483. The green sunfish tolerates a vide range of conditions, but
does best where few other sunfishes occur. It is adaptable f .or survival
in fluctuating environments, since it tolerates extremes of t .urbidit;r,
dissolved oxygen, temperature, and flov.
484. The longear sunfish is characteristic of clear streams vith
sandy or rocky bottoms and permanent f'lov. It is more common in
streams than in large rivers. Like other sunfishes, it avoids strong
currents and is usually found in pools and backwaters adjacent to the
stream channel. In most environments, when longear sunfish are camnon,
··.green' sunfish are rev.
·.~ · ~. 485. ·The rock bass CODIDonly occurs in streams. Permanent :flow,
low turbidity, abundant cover, and silt-free bot toms are its basic
requirements. It is usually found near boulders, subme·rged logs, and
t ·ree roots· vhere there is a slight to mod.erate current. A deep rocky
pool iDJmediately below e. ri.ffle is a f'avored spot.
· 486. Reproduction. The true sunfishes appear to have similar
spavning.habits. Fish begin nesting in the spring vhen vat.er tempera-
tl;U'es are about 21 °C. Spavning reaches a peak in June but orte.n con-
tinues into August. Nesting occurs on almost any t .ype of bott om.,· but
gravel is preferred, Nests are usually in water 0.3 to 0.6 m deep and
consist of roWldish depressions with a diameter about t .vice the length
of t -he. male parent. Many nests are coDI!lonly close togetbe.r and in a
limited area. The green SWlfish is less colonial than some of the
other sunf'ishes in its nesting habits. The, male guards the nest unt.il
the e.ggs hatch but does not guard. the fry once t .hey leave the. nest.
136
·.
Because. of their similar spawning habits, the various sunfish species
often crossmate and produce hybrids.
487. The nesting season of the rock bass coincides with that of
the smallmouth bass and precedes that of the sunfishes. Nests have been
observed as early as the first week of April and as late as early June
in Missouri, but in any given year the season seldom lasts more than
one month (Pflieger 1975). Nesting begins when stream temperatures
range between 12.8 and 15.6°C. The male rock bass fans out a saucer-
shaped depression 200 to 250 mm in diameter over a bottom of coarse
sand or gravel~ Nests arc in water from 0.3 to 1.5 m deep, usually
near a boulder or other large object, and often where there is a slight
current. The rock bass is a solitary nester, in contrast to the true
sunfishes, which tend to nest in colonies.
488. Food. The diets of true sunfishes and rock bass are gener-
ally similar. Young of the year feed on zooplankton and immature
aquatic insects, and older fish on aquatic insects, supp.leme.nted with
small fish, crayfish, and snails. Feeding is most intense during the
'early morning and in the evening. •··~·~.·
489. Age and grovth. Growth of the bluegill varies considerably .
from one body of vater ~o another. Growth is usually slower in streams
than in ponds, lakes, or reservoirs. In most Missouri waters, the
bluegill reaches a length of 150 mm and a weight o:f about 70 g by the
end of its third or fourth summer of life. A 215-mm bluegill weighs
about 225 g. Bluegills commonly reach a length of 240 mm. and a weight
of 340 g (Pflieger 1975).
490. The green sunfish attains lengths of about 43, 81, ll9, 150,
and 193 mm at an age of 1 through 5 years, in the Salt River, Missouri
(Purkett 1958a). A 150-mm green sunfish weighs about 85 g; few indi-
viduals exceed .a length of 230 mm or a weight of 340 g.
491. In Missouri streams, the longear sunfish attains a length of·
about 33 mm its first year and 64, 91, 109, 122, and 127 mm in succeed-
ing years (Purke,tt 1958b). The maximum length and weight are, about
175 mm and 128 g.
137
. ~ .
·;
·.
492. Rock bass from Ozark streams in Mis,souri average 41 mm in
length by the end of their first year of life and attain lengths of 86y
140y 178, 203, and 216 mm in succeeding years (Purkett l958a). Few
live more thar. 5 or 6 years, but they commonly attain a length and
veigh~ of up to 280 .mm and 454 g.
493. In s·ummary, growth of the true. sunfishes varies considerably
from one water body to the next, and st\Ulting occurs in crowded popula-
tions or vhere water is continuously turbid. Generally the bluegill,
rock bass, and green S·Wlfish attain the largest size.
T::-ue sun:'ishes in tailwaters
494. ··The abundance of sunfishes in tailwaters is variable and
depends on recruitment and the available habitat. The occurrence of
sunfishes in tailwaters below Tenness~e Vall7Y Authority storage reser-
voirs was found t .o depend on fish present in the river be,fore impoWld-
ment, fish entering the tailvater from the reservoir above, and migra-
tion into the tailwater from tributary streams or reservoirs dovnst.ream
(Pfitzer 1962). Cavender and Crunkilton (1974) reported bluegills and ·
,, vhite 'crappies being carried over th!! spillway of Hoover Dam, Ohio,
·.~and e.stablishing small populations in the ·tailvater. '. Bluegills vere
also periodically transported over spillways into the. tailvaters of
Urieville Lake and Wye Lake, Maryland, ~nd r,;;rainfe Lake, Obi·~ ( Clal'k
1942; Elser 1960).
495. Sunfishes generally prefer areas vi th instream cover, lov
currents_, and maximum water temperatures above 21 °C. SWl:fish popula-
tions are usually depressed in tailvaters that are cold, or have high
turbidity or little instream cover. Bl·uegills, longear sunfish, and
green sunfish were collected in Norfork tailvatery Arkansas, in 1950 -
( rese:rvoir impounded in 1944), but were lac.k.ing in collections made in
1959 (Hoffman and Kilambi 1970). Brovn (1967) fO ·Wld several sunfishes
in the same drainage below the never Beaver Dam in 1965 (reservoir
impounded in 1961). Apparently several years are required before the
reduction in temperature eliminates s\Ulfishes from these cold
tail waters. Table Rock tailvater (Lake Taneycomo), Missow·i, vas con-
verted from a warm to a cold tailwater when hypolimnetic discharges
138
..
.·.·
: -..
. . ,
"J.·.
, .....
.. '
-~
~re begun in 1959. Bluegills were the only varmvater species to re-
m&in abundant after the c.hange to cold water. Most of the blue gills
were captured at the downstream end of Lake Taneycomo, where solar
wa:rmlng and some thermal stratification occurred (Fry and Hanson 1968).
Bluegills and longear sunfish composed over 50 percent of the total
numbers of' fish collected by electrofishing in Nolin tail water,
Kentuc.ky, in 1965 and 1966. The abundance of sunfishes in the tailvater
was due primarily to export of fish from the reservoir above (J. P.
Carte·r 1968b). A cha.:nge from epilimnetic to hypolimnetic release and
the stocking of trout in the tailvater in 1970 and 1971 resulted in a
reduc.tion of the sunfish harvest. The sunfish catch from 1968 to 1971
declined from 79.4 to 10.7 percent of' the total number of fish caug!Lt
and .from 44.6 to 3.4 percent of the total fish weight (Charles and
McLemore 1973). Reports of sunfishes in other cold ta.ilvaters are
limited. Bluegills, green sunfish t and redear sunfish compo•sed only
5 perc.ent o·f the 1975 fish coi!IDuni ty in Dale RoLlow tail water, Tennessee
(Bauer 1.976).
496. ·Studies on several va.rm tailvaters suggested that sunfishes ~..;.::.~ · ..
can be _important in the fi.shery. Bluegills w:ere estimated to be '8, 12," 7
and 13 percent of the angler catch at Lake of the Ozark.s, Pomme de
Terre, and Stockton tailwaters, Missouri. Both Lake of the Oza.rks and
Pomme de Terre have epilimnetic discharges, resulting in ma.xi.mum· .;,a_ter'
temperatures of about 29°C (Hanson 1974). A highly significant corre-
lation betveen total annual discharge and annual average cate:h rate .
'·
W'a'S .found at Pomme de Terre. Hanson's findings agreed with the con-
clusions of Moser and Hicks. (1970) that tailvater fisheries are sup-
ported by fish from the reservoir (Hanson 1977). Carter (1969) stated
that sunfishes in the Barren tailwat.er, Kentucky, were mo-re abundant
. when water was released from the epilimnion rather than from the
hypolimnion. The warm v:3.ter, in combination with the abundant instream ·
cover, accounts for the increase of sunfishes. Of the fish seined
below Lake Carl Blackwell, Oklahoma, 15 percent were sunfishes (long eat",
orangespotted, and green). The longear sunfish was most abundan.t in
July when it was favored by reduced turbidity and stabilized flovs
139
. · ....
belov the dam (Cross 1950) • Not all varm tailvaters :provide good
sunfish habitat. Moser and Hicks (1970) found that sunfishes made up
only 1. 5 percent of the fish biomass and 3. 0 percent of fish numbers
in the stilling basin of an Oklahoma reservoir. Lack of cover may have ........
been responsible for the lov abundance of sunfishes. Fritz (1969)
reported that bluegills made up 4.4 percent and green sunfish 2.6 per.-
cent of the angler catch in Carlyle tailvater, Illinois.
497. Sunfishes are important to the fisheries in some"cool
tailvaters. Longear sunfish vas the most common species taken by
anglers in Broken Bow tailwate:-, Oklahoma ( 36 percent of the catch), and
was second in biomass· ( 17 percent). However, more longear sunfish vere
captured in the river above the reservoir than in the tailvater. Weekly
temperature means averaged 3. 8°C lover in the tailvate.r than in the
river upstream. Apparently the cool vater and fluctuating flovs. in-
fluenced the harvest of sunfishes in this tailvat~ (Andrews et al.
19'74) . Cavender and Crunkil ton ( 1974) reported that a small conc·entra-
tion of rock bass exists in Hoover tailvater, Ohio; the authors be-
t
lieved that the rock bass stay in the tailvater because of the abun-
.. dalice of forage fish and crayfish. _ ...
498. The food habits of bluegills and longear _sunfish fro111 Wilson
Dam tailvater, Tennessee, vere studied in the spring of 1977 (Warden
and Hubert 1977). Fish eggs made up 67.2 percent of the total number
of food items and 59.2 percent of the total volume in bluegills, and ... . ..
56.1 percent by number and 3.7 percent by volume in longear sunfish.
Insects vere abundant in the stomachs of both species. Insects ac-
counted for 27.1 percent by number and 32.1 percent by volume of food
items in bluegills, and 23.0 percent by number and 22.2 percent by
volume in longear sunfish. Insects eaten vere of the orders Diptera,
Coleoptera, and Trichoptera and, of these, chironomid larvae and mayfly
nymphs composed 90 percent of the tctal number and volume. Ot.ber items
found in the stomachs vere decapods, larval fish, iaopods, mollusks,
arachnids, and annelids.
499. Grovth of bluegills in Hartwell tailvater, South Carolina,
did not vary from that of fish downstream or from those captured in &>n
140
.\
" I
..
·-
.~. :-
·'·
unimpounded. control stream. Apparently temperature fluctuati.ons and a
temperature range of 6.1 to 16.8°C in the Hartwell tailwater did not
adversely affect growth (Dudley and Golden 1974), although Fry and
Hanson. (1968) stated that growth of warmwater fish (including bluegills)
was reduced. in a cold Missouri tailvater (discharge temperature 4.4-
15.60C).
Crappies
500. The white crappie and black crappie may both occur in
tailwaters, and they have similar life histories.
501. Habitat. White crappies are found in ponds, lakes, reser-
voirs, and slow-moving streams and rivers. In reservoirs, they are
often found in areas having standing timber or other cover, and a·t
other times they frequent dee,per va·ter, commonly occurring at depths
of 4.6 m or more. Young crappies are often found over open vater of
considerable depth. In streams, the white crappie is most abl.Uldant in
the deeper pools or in 'backwater areas away from the main current. It
avoids streams that are excessively turbid and those kept continuously
·cool ·.ay· tlov from spriligs. " ...... ~ · "':.;'"_'~'?'· .-
. ; .,·~· 502. T.he black crappie requires habitat similar to that o·r the .. : ·
white crappi.e except that it is less tolerant of turbidity and silta-
tion. In reservoirs, the black crappie is noticeably more abundan·t in
embayments fed by the clearer streams. In streams, black crappies
require clear water, absence of no·ticeable current, and abundant c.over.
503. Reproduction. Crappies begin spawning in April or May,
when the vater temperature rises to about 15.6°C. In reservoirs,
s.pavning occurs in shallow areas of coves protected from wave action;
many nests are sometime•s concentrated in the same cove. Nests are
prepared by the male on a variety of silt-free substrates in water 0.1
to 6.0 m deep. Sites with nearby logs or other large objects are
favored locations for nests. The location of the nest is i 'ndicated
only by the presence of tbe male. Eggs hatch in about 3 days and the
try remain in the nest several more days. Fry do not school after
leaving the nest.
. 141
: : rl
-·
T'
504. Food. The diet of yoWlg crappies consists mainly o·f zoo-
plankton, and that of adults includes zooplankton, aquatic insects,
and small fish. The proportions of these · food. items in the adult diet
vary with locality, season, and age of the fish. Small gizzard shad
and threadfin shad are important foods of adult crappies in many reser-
voirs.
·505. Age and grovth. According to Carlander (1977), the average
calculated total lengths of white crappies at ages· I to VI from all
are.as of the United States are 78, 158, 213, 257, 290, and 304 mm.
Average weight of a 4-year-old white crappie is about 300 g.
506. Grovth in length of black crappies_is generally less than
that of-white crappies in the same waters (Pflieger 1975). However,
since the black crappie is heavier at any given length ·than the vhite
crappie, grovth in weight differs little between the two species. Fev
crappies live more than 3 or 4 years, but oceasional individuals live
as long as 8 or 9 years. Maturity is reached during the second or
third summ.er of 1i fe.
·Crappies in tailvaters ·-•
•··-507. \-.'hi te crappies and black crappies are important in any ·
tailvater fisheries. When crappies are abundant in a reservoir, they
are often carried through the dam and remain in the t .ailvater. Crappie
abundance in a tailvater appears to be affected by water temperat.ure,
season, and type of dam discharge. . .•
• 0 ~ • .. .. • •
5'08. Crappies are often abundant in warmvater tai.lvaters and. can
contribute substantially to the fishery. White crappies vere"estimated.
to mak'!! up 56 percent of the angler catch at Lake of the Ozarks
tailwater, Missouri, in 1965-74. A high correlation vas found between
estimated number of fish caught and the number of days the flood gates
were open at the dam (Hanson 1977). Crappies ·were estimated to be 41
and 54 pE.rcent of the m.UDber and 35 and 49 percent of the veight of the
fish taken by sport fishermen during varmvater releases at Barren and
Nolin tailvaters, Kentucky, in 1970 and. 1971 (J. P. Carter 196&;
Carter 1969). P. Carter (1968a) reported that before reservoir
construction in 1965, crappie populations in Barren and Nolin rivers
142
' '
• ·.~ l
'· .. I
.. t
:.,r •,
.. .·
·'·
.. _ ... . ..
were low and. contdbu.ted little to the fishery. He attributed the
increase in abund&Oce after impoundment to fish that vere produced. in
the reservoirs and moved dovnstream through the dam.
509. Tb.e occurrence of fish in stilling bas.ins belov va.rmwater
:release dams has been examined in tva studies: Pfitzer (1962) col-
lected 120,000 crappies weighing 10,884 kg from 1.0 ha of water below
Douglas Dam in Tennessee on October 30, 1953; Hall and Latta (1951)
stated that 23 ,percent of the fish found in the stilling basin below
Wister Dam ,, Oklahoma, in August were white crappies.
510. Several investigators have reported on the movement .and
seasonal changes in abundance of white crappies in warm tailwaters.
At Kentuclcy L&ke tailwater in Kentucky, 3552 white crappies were
captured, tagged, and released fran January to December 1953'. Anglers
• I • I
., recaptured_ 113 fish (3.2 percent) of which 95 (84 percent) were taken
within 1.6 km of the release ·site (Carter 1955a·). A concurrent tagging,
study in Kentucky Lake shoved little movement of white crappies (on the
, .... basia. ~: recapture~ of 5 of 1752 marked fish) through. the navigati?I?-
locks into the ta'ilwater (Carter 1955a). Anglers at Levis and Clark
Reservoir and its1 tailvater, South Dakota and Nebraska, returned 42
tags fran 288 white crappies tagged in the reservoir. or these, 12
(28 percent) were tram fish captured in the tailwater (Walburg et al. ··
1971). White ·crappies were abundant in the tailwater belov Lake Carl
Blackwell, Okl.ahana, from October 1947 until March 1948 because flows
were srtable and many fish escaped from the ·reservoir. Between
Kovember and Janu&l"y, 139 white crappies were tagged and released in
the tail waters. Most tag recoveries ·were reported during the •winter,
'axld we·re made in the tail waters. High water releases from the reser-
voir during March 1948 apparently caused the crappies to leave the
tailwater, since.,only tva tagged fish were captured during the subse-. ..
quent spring and summer (Cross 1950). An increase in crappie abun-
dance during. fall 1965 at Barren tailwater, Kentucky, was associated
with the fall reservoir dra:wdo\ltl and the high water discharge into the·
tailvat er (J. P. Carter l968b). There is a large populat ion of white
crappies and black crappies in Hoover Reservoir, Ohio, and many young
143
.......
....
are carried over the spillway and into the tailwater (Cavender and
Crunkilton 1974).
511. T.he change from hypolimnetic · (coldwater) to epilimnetic
(warmwater) release (or vice versa) at some dams has affected the
abundance of crappies in tailwaters. At Barren tailvater, Kentucky,
crappies composed 13.4 and ll. 6 percent of the catch during hypolim-
netic releases in 1968 and 1969, but 41 and 44 percent during epilim-
netic releases in 1970 and 1971 (Charles and McLemore 1973}. The
construction of Table Rock Dam, Missouri, changed the downstream Lake
Taneycomo from a warmvater to a coldwater habitat. Test netting in
Lak.e Taneycomo before and after the coldwater intrusion showed ·a
reduction in white crappie abundance from 6.5 to 0.9 fish. per net day
(Fry and Hanson 1968). Apparently the cold vater made the tailwater
habitat 'less.suitable for the white crappie.
512. Small crappies are common forage for predatory fish. Com,bs
( 1979}, vho studied the diet of 164 adult striped ba.ss collected from
· the tailva:ters of Keystone Dam, Oklahoma, in 1974 through 1976, found
tb&t frequency of occurrence and percentage of total volume of ·vbite
crappies in stomachs vas 10.4 and 5.8 percent, respectively. Walburg
~~ &1. (1971) reported tb~ occurrence of white crappies in stomachs of
walleyes and saugers collected in Levis and Clark tailvater, South . . .
Dakota and Nebraska.
5·13. Food of black crap'_;>ies from Holyoke Dam tailwa~er, Massa-
chusett.s, in 1972 consisted mostly of spot tail shiners and insects
(69.3 and 27.2 percent of total food volumes); the frequency of occur-
rence of fish, insects, and zooplankton in stomachs vas 44, 68, and 42
percent, res9ectively (Jefferies 1974).
514. Studies of the growth of crappies in tailvate1#:has received
little attention. Carter (1955b) reported that white cr~pies in
Kentucky Lake grew faster than those in the tailvater. B;rore
deep-vat er releases from a Missourireservoir converted the dovnstream
Lake Taneycomo into a coldwater habitat in 1959, the average length of
4-year-old white crappies vas 338 mm, but after the change in 1963, it
was only 211 mm (Fry and Hanson 1968).
144
~ . . ~
.. i
I
.·
•• t
515. In ·a report. on crappie gonadal development in tailvaters,
3 of 74 vhite crappies collected belov a Tennessee dam, betveen July 29
and September 1, 1941, vere immature.; the rest vere ripe, but none had
spavned. Apparently the cold vater (< l0°C) had disrupted their repro-
ducti.ve cycle (Eschmeyer and Smith 1943).
Percidae (Perches)
516. Th~ perch family is one of the largest groups of North
American freshvater fishes. Among them are three popular game fishes-
valleyes, saugers, and yellov perch--and a large number of smaller
fishes knovn collectively as darters. The three game fishes are repre-
sented in Europe by the same or closely related species. The .darters
are native only to North. America.
517. The closely related walleye and sauger both occur in rivers .
and -are important in some tailvaters . The yellow perch is most oft en
found in lakes but it is also abundant in backwaters of large rivers.
::V~~;t'!.·~~:-:,;:.~::.~:t~~-)·~_;:r;··It 'is seidom fo~d in small streams an.d usually does ~ot occur i n··:; ::o:-_·.:;.:-·.-r ·
, ..
''·
.. :~'. ~ ..
,• .. a!;~·:t• •.
''r··
., . '
. ..
.,•
. .
tailwaters·ana, therefore, is not discussed further here. Darters are :
adapted for life in svi:rt-floving sections of clear, rocky streams and
. ·are common inhabitants of many tailwaters. The percids are discussed
under two groups-(a) walleyes and saugers, and (b) darters •
Walleyes and saugers
518. Habitat. Walleyes and sauge.rs inhabit the open water of
large, shallow lakes on slow-nowing rivers . The habitat requirement s
of the two species are similar, except that the sauger is m<:~re tolerant
of high turbidity and is o:rten found in areas with strong current. The
sauger is more common in habitats with silted bottoms, vhe1·~a~ valleyes
prefer habitats with gravel, bedrock, and other types of firm bot~om.
Tubb et al. (1965), vho studied fish distribution in the Sheyenne River
in. North Dakota, found walleyes in pools 0 .9 to 5.5 ~ deep, but most
commonly in pools dee·per than 2 . 4 m. The sauger vas taketl in only one
pool, vhich vas 2.4 m deep.
145
.····II: a
519. The sauger feeds more actively during the day, vhereas tb~
walleye is more crepuscular. The walleye is light-sensitive and is
usually found in deepwater pools during the day, especially when water
is clear. Both generally occur in loose aggrega,tions of a fev to many
individuals. They range over a vide area, rather than restricting
activities to a definite home range.
520. ·Reproduction . Spavning occurs at night over a 2-wee:k period
in the spring when water temperature exceeds 5.6°C. Spavning is com-
monly preceded by move.ments out of larger rivers and reservoirs into
tributaries, the males moving to the spawning grounds before the
females. There is some evidence that these species tend to return to ·
a "home" spawning area in successive years. Spavning· occurs on ri ffle.s
or rocky areas below dams in streams and along rocky wavesvept
shorelines in lakes and reservoirs. Females are accompanied by several
males during spawning, and eggs are scattered at random. Tbe adhesive
eggs stick to the substrate, and tAtching occurs in 12 to 18 days,
depending on water temperature. Newly hatched la.rvae are semi buoyant,
and those produced in streams are therefore subject to dovnstream
transport. ·' -. ' ::. ,.; ... ·., ... _~ .. -.
521. ~ Small crustaceans and insects are the food of walleye
·and sauger frJ. Insects are a significant food item throughout life,
but .fish are the principal food of a~~ ts. They apl'&7.~ntly eat any
specie.s •>f fish readily available to them.
522/ Age and growth~ The sauger grows more slowly than t ,he
walleye and does not attain as large a size. Fish from the northern
portion of' the range grow slower a;.1d live longer than those from more
southern waters. Females attain greater lengths and 1i ve longer 'than
males. Newly hatched larvae of both species are only a·oout 7 t ,o 8 Dill
in length, but under ideal conditions may attain lengths up to 254 mm
by the end of the first year. Pflieger ( 1975) .reported that the
average length of walleyes frcn the C\lrrent River in Missouri is 200 11111
at the end of the fir .3t yes.r and 610 11111 at the end of the seventh year.
The usual life span is 7 or 8 years, but muc·b older individuals are
not uncommon.
146
I.
. -•• ...
.. -. '. , ..•
523. Vasey ( 1967) reporte.d that the saugers in the Mississippi
Ri,·er in Iova reach a length of 145 mm in the first year and 515 mm
after the seventh year. The usual life span of saugers in the South
is 5 o.r 6 years, but some live to 12 or mo:re years in Canadian waters.
W'a.lleyes and saugers in tailvater·s
524 •. 'Walleyes and saugecrs commonly occur in tailwaters below dams
in many river systems. Their occurrence is often seasonal, caused by
the blockage of upst.ream migration or passage downstream from the reser-
voir above. Concentration of prey fishes attracts walleyes and saugers
to tailvaters .
. 525. 'Walleye numbers have increased belov a number of dams ill the
years following construction. They are the second most nume.r ·ous
species in East Lynn Lake tailwater, West Virginia (Pierce 1969). They
have increased in abundance in SUDDDersville tailvater, 'West Virginia
(Goodno 1975); below four hydropower impoundments on the Au Sable River,
Michigan (Richards 1976); and in the tailwater belov Stockton
hydropower dam, Missouri, where they composed 28 percent of the catch
··-by anglers in 1974 as compared with only 9 percent in 1 ,972 (Hanson ~:·.
1974).
~: .. .,
526. Saugers are highly migra·tory, moving up.stream as much as
380 km in 18 days, through the navigation locks in the Tennessee River
main-stem dams (Cobb 1960). Blockage of upstream .migration has pro-
vided significant winter and spring fisheries in most varm main-stem
dam tailvaters and in some cold tributary dam tailwaters on the
Tennessee River system (Pfitzer 1962). An estimated 88,703 saugers
were caught between November 1959 and March 1960 in Pickwick Dam
taillrate.r {Trenary 1962). Cobb (1960) reported there was no sauger
fishery in the Tennessee River until the main-stem dams were con-
structed.
527. The sauger fisheries in cold tributary tailvaters of the
Tennessee Riyer system are generally smaller than those below the
main-st em dams. Periodically som.e saugers migrate upstr-eam from 'Watts
Bar Reservoir and congregate in the cold Norris tailwater (Eschmeyer
1944; Eschmeyer and Manges 1945). Large numbers of saugers vere also
147
I
. ..
i
I.
I
..
..
caught in the upper 23 kn of the cold Chilhowee Dam tailwater on, the
Little Te·nnessee River. In 1964 and 1965, most were taken from
December to March and composed 16 percent of the creel. In the
downstream portion of the tailwater, 24 to 46 km below the dam, saugers
were less abundant than in the immediate tailvater, but constituted 80
· percent of ~he anglers' catch (Boles 1969).
528. Passage of fis.h over dams from re·servoirs upstream is also
· impor tant in establishing walleye and sauger fisheries in tail waters.
An estimated 19,102 walleyes passed into an Ohio taih:ater over a 5-
year period (Armbruster 1962). A large percentage (42 percent) died
. from broken backs and pressure damage while pasS'ing through or over the -: . . .
dam, but 58 percent survived ,passage into the tai lwater. Of tag re-
coveries from walleyes tagged in the reservoir, 30 percent c.ame from
t.he tailvater. Studies on the Missouri River bave s ·hown that· large
·numbers of young-of-the-year walleyes and saugers--up to 700,000 in
24 hours--moved out of Lewis and Clark Lake, South Dakota and Nebraska ,
and into the tailwater (Walburg 1 971). Mark-and-recapture studies
indica.ted that :some adult sauge-rs also move from the reservoir int o
-:the tail:water (Walburg et al. 1971}. Additionally~ the tailwater
walleye fisheries in Hoover tailwater, Ohio, and Canton Reservoi r
taU water, Oltlahooaa, are the result of the export of fish from the
reservoir (Moser and Hicks 1970; Cavender and Crunkilton 1 974). A
related species, the Volga pike-perch, has increased in the Kuibyshe•t
tailwater, U.S.S.R., after successfUl reproduction in the reservoir
(Sbaronov 1963).
529. Other factors, including water depth and. temperature, aff~ct
tailwater walleye and sauger fisheries. The in.cre.aae in water depth vith
a probable increase i n water temperature in the l over sections of Dal e
Hollow tailwa.ter, Tennessee, due to inundation by Cordell Hull Reser-
voir, was foll owed by the appearance of both walleyes and aaugers
(Bauer 1976). Spor t fishing success for walle yes in Lake Taneycomo
tail water, Missouri, is dependent on the wate.r level of Bull Shoals
Reservoir, which inundates the tailwater. Best catches occurred when
Bull Shoals Reservoir was 0.6 to 3.0 m below power pool level. Catches
148
'
..
~-
.. ',J.·'t .
.-. .. -,. ~ . _ ...
,.,. .. _
progressively declined when water levels were either above or below
this range (Hanson 1969) •
530. Water temperatures. in some col~ tailvate.rs have had a nega-
tive effect on vall eye populations. Lowered vater temperature in a
'Korth. Carolina tailwater eliminated the walleye fishery (Dendy and
Stroud 1949). Lov water temperature in Table Rock tailwater, Missouri~
has also affected the walleye catch. A rapid temperature increase of
5.6°C in the tailvater due to flood. flows spilling over the dam re-
sulted in an immediate increase in'feeding activity and consequent
increase in wall.eye catch (Fry 1965).
531. Reproduction of saugers has been adversely affected in some
cold tailvaters. Saugers in a Tenness ·ee tailvater have sbovn signs of
.resorbi.ng eggs. This vas attributed to lov water temperatures~ which
ve·re generally less than 10.0°C (Escbmeyer and Smith 1943).
532. Flow regulation can influence walleye reproduction hundreds
of kilometres downstream. Reduced winter flov·s from Bennett Dam. on
the Peace-Athabasca River in Canada allowed the inlet to Lake Richardson
' to · t'reez~., 'thereby delaying access of walleyes to spawning area• in the :~:
spring (Peace-Atbabasca Delta Project Group 1972; Geen 1974). A similar .
situation was reported below the Volgograd li;,•droelectric Dam, U.S.S.R.
Reduced spring f'lovs caused a deterioration of pik~-perch spawning
. habitat far downstream in the Volga River Delta on the Caspian Sea
(Orlova and Popova 1976) •
533. Water-level fluctuations in tailvaters have a negative in-
fluence on sauger reproduction. Year-class strength in Fort Rand all ·
Dam tailvaters, South Dakota, vas 15 times greater in years when vate.r
levels fluctuated only 0.8 m/day than in years when fluctuations were
1.4 m/day (Nelson 1968). Apparently, reduced water-level fluctuat ion ·
resulted in greater survival of eggs and larvae. To increase sauger
abundance, Walburg (1972) recommended that water releases from Fort
Randall Dam be not less than 566m3 /sec during the spawning and egg
incubation period.
534 . Walleyes have been stocked in some tail waters where natural
reproduction does not occur. A 26-km stretc h of river be,low the
. ' -.
I
I.
I
i ,.
I
I
Boysen Unit Dam, Wyoming, has provided a good wal~eye fishery as a
result of stocking (U. S. Bureau of Sports Fisheries and Wildlife
1969}. Hicks (1964} recormnended stocking walleye fi,ngerlings instead
of walleye fry in Tenk.iller tailwater, Oklahoma, because-··of·"Wlsuitable
zooplankton supplies caused by intermittent water releases. The recom-............
mended stocking of fingerlings was appar ently successful, since both
walleyes and saugers nov occur in the tailvater-(Deppert 1978").
535. Food habits and grovth of walleyes and saugers in tailvaters
·· are not well documented. An examination of six walleyes collected from
..: Holyoke Darn tailvater, Massachusetts, shoved that fish made up · 96 per-
· cent of the total volume of food in stomachs (Jefferies 1974). Saugers
in Chilhowee tailwater, Tennessee, preyed heavily on stocked rainbow
trout during the spring spawning run (Boles 1969). Food of walleyes
and. saugers from Levis and Clark tailvaters, South Dakota and Nebraska,
consisted primarily of gizzard shad, emerald .shiners, yellow perch,
vhi.te bass, and white crappies (Wa.lburg et al. 1971). The grovth of
.wa11eyes and saugers in Levis and Clark Lake tailvater vas superior
·: to that ·in t~e reservoir; for fish of si~la.r lenCtbs, ·the weights o~ · ·
_;-·' . _, •. ~ . . .· .. . · .. ~; ,··j. .,. . . ..
walleyes and saugers vere respectively 7 and.l2 percent greater in
the tailvater.
Darters
536. According to Bailey et al. (1970), 109 species of darters
are found in the United States and Canada. Comparatively .few ar·e
·.· mentioned in the tailwater literature. A general description Qf.
I darter life history is presented because of the large number of
species.
537. Habitat . Most darters are found in c l ear, smal·l -to medium-
sized streams vi th permanent flow and clean, gravelly·, or rocky bottoms.
They are most often found in the deeper sec tions of ri.ffles ,, but e.lso
occur in rocky pools having no perceptible current. Some spe cies are
.f
more tolerant to turbidity than other s. The young of most species can
be found in quiet-water areas associated vith leaves,·sticks, and
organic debris.
150
..-; :-!' ·~ .... .;. ••• :.:: ; ~.
.· , .....
. ...... . , .... , ·····.'"··
.......
.....
..
538. Darters are adapted for life in svift-floving streams.
They sink immediately to the bottom vhen they stop svimming, and the
press of the current against their enlarged pectoral fins tends to hold
them in place. Darters are usually found beneath or betveen rocks and
are thus afforded protection from the direct action of the current.
When moving from place to place, they proceed by a series of short
darts.
539. Reproduction. Most darter's usually spavn in lat~ spring
over a sand or gravel bottom in vater about 0.3 m deep having moderate
current. Eggs are laid and fertilized in a depression on the stream
bottom, vhere they hatch in about 21 days at 21°C. Eggs and larvae
receive no parental protection.
540. Some darter species attach eggs to strands of filamentous .
algae or aquatic mosses and males establish territories. Breeding
males of still other species seek out and occupy cavities beneath ·
rocks. Ripe females enter the cavity and deposit their eggs, vhere
they adhere to the underside of the rock. The male stays vith the
• ~ -~~ ·,;· .. : .. 1 .•• • • .t:~;.:·~~.:~. ;~,hit.'~ .. eggs until. they hatch. ..,.., .. · ,;· .
541. Food. . Darters are carnivorous, feeding principally on
insects and other small aquatic invertebrates.
542. Age and growth. Lengths of adult darters other than
logperch usually range from 64 to 89 mm, vith a maximum of about 100
mm. Males grov more rapidly and attain a larger size than females.
Most are mature in the first spring after hatching and fev live longer
than 3 year~. The logperch, the largest darter, usually ranges in
length from 102 to 152 mm, but sometimes attains 178 mm.
Darters in tailvaters
543. Darters have not been studied extensively in tailvaters.
They flourish in a variety of.environments, and some have become
established in cold tailvaters. Many darter species, particularly
the orangethroat darter, rainbov darter, and logperch, are abundant
in Beaver tail vater, Arkansas ( Brovn et al. 1968; Bacon e·t al. 1969;
· Hoftman and Kilambi 1970) . Their abundance may be due to the uns·table
composition of the fish population in this relatively nev tailvater.
151
-------· --------... ·-. -·----------.... ..---.... -------·-·--·--...___,...,. ____ ...,... ..... -...... -··-. ---
...
Darter numbers are reduced in older tailwaters in the same drainage
(Brown et al. 1968; Hoffman and Kilambi 1970).
544. The relatively low water temperatures (14.4-21. 7°C), low
turbidities, mixed gravel-bedrock substrates, and high dissolved oxygen
levels in Hoover tail water, Ohio, provide excellent habitat .for some
_darter species. The logperch, greens ide ·darter, rainbow-dart-er.., and
-•banded darter ·are all abundant, and the blacks ide darter, johnny darter,
and fantail darter also occur there (Cavender and Crunkilton 1974).
545. The logperch, gilt darter, and band.ed darter were all abun-
dant in the cold Chilhowee tailwater in Tennessee. The logperch was
also nwmerous in the cold Norris tailwater (Hill 1978). The tessellated
darter was dominant in the cold Rocky Gorge Dam tail water, Maryland
(Tsai 1972). The orangethroat darter was the seco.nd most abun4ant
s .pecies in the cold tailwater below Canyon Dam, Texas. The reduced
temperatures in this taUwater appear to have extended the winter and
spring breeding season of this species, and reproduction now occurs
throughout the year (Edwards 1978).
546. Only one report on the age and. growth of darters in • _
. tailvaters was found·. Tsai (1972), who studied the tessellated darter
in Rocky Gorge Dam tailwater in 1967, found that the mean. standard
lengths of females at ages I, II, and III vere 35, 47, and 55 DID;
males were 37 mm long at age I and 50 .mm at age -II.
Sciaenidae (Drums)
547. The drum family contains many important marine fishes; only
one is a freshwater species, the freshwater drum.
Freshwater drum
548. Habitat. This fish is found in large, shallow lakes and
large, slow-moving r:l.vers. It is usually found in the larger pools of
streams and in lakes and reservoirs at depths of 9.0 m or more. The
freshwater drum avoids strong current, 1 s usually found near the bottom,
and is tolerant of high turbidity. It is particularly common in the
~tissouri and Mississippi rivers and t-he dovnstream sections of their
1 .52
I ~.'";. ' i"-.,
major' tributaries . It is also c011111on in Lake Erie and in many reser-
voirs.
549. Reproduction. Spawning of the freshwater drum occ·urs in
late spring or early summer, vhen water temperatures reach about 18°C.
Spawning occurs over a period of about 6 veeks (Svedberg and Walburg
1970). .Eggs are fertilized in the open water and :t"loet until hatcbinf).
They hatch in about 36 hours at 21 °C; nevly hatched larvae are 3. 2 mm
long. The larvae are semipelagic until they are at least 15 mm long.
The vide distribution of the freshwater drum in floving-vater systems
is related to the pelagic state of their eggs and larvae.
550 . Food. The diet of freshwater drum consists mainly of fish,
crayfish, and immature aquatic insects; mollusks are eaten if available.
·Young of the year eat mostly zooplankton and chironomids; as fish in-
crease in size, larger aquatic insects become important.
551. .Age and growth. In Missouri streams, freshwater drum
average 112 mm in length by the end of the first year of life and 2o6,
269, 315, 353, and 378 mm in succeeding years (Purkett 1958b). On the
average, a· 330-mm · t1 sh weighs about 4 50 g and a 400-mm fish about · 900 "t;;.· ..
g. Most drum caught by fishermen veigh 900 g or less, but individuals
weighi.ng up to 1~.9 lt.g are occasionally taken. The mAximum life span
is at least 13 years.
Freshwater drum in tailwaters
552. The role of freshwater drum in tailvaters has not bee.n
studied extensively. Several reports deal vith their occ·urrence in
warm and cold tail waters. They are relatively common in the warm
Keystone Dam tailvater, Oklahoma, v~ere they are .eaten by striped
bass (Combs 1979). They are abundant in Levis and Clark Lake, a
main-stem Missouri River reservoir on the South Dakota-Nebraska
border, and large numbers of young of the year less than 25 mm long
pass into the tailwater vith the discharge during the summer (Walburg
1.971). · In spite of the large numbers of young lost from the reservoir,
adults are relatively uncommon in this warm tailwater (Walburg et a.l.
1971). Apparently fev of the young carried downstream in the river
flow later return to the tailwater. Freshwater drum made up 10 percent
153
of the total sport catch in the cool Pomme de Terre tailvate:r, Missouri,
from 1965 through 1974 (Hanson 1977). They were also common in the
cold Tenkiller Dam tailwater, Oklahoma (Deppert 1978). The numbers of
freshll!lter drum in a Mi ·ssouri tailvater have declined in 'recent years
because water temperatures have decreased since completion of the
upstream dBJII (Hanson 1969).
Cottidae (Sculpins)
551 The sculpins are bottom-living. primarily marine fishes, of
arctic and temperate seas; several genera are found in fresh waters of
the northern hemisphere. This discussion vill be limited to the
mottled and banded sculpins, vhich occur in some streams.
Scul"Dins
554. Habitat. The tvo sculpin species often occur together
because tbeir requirements are similar. The mottled sculpin is usually
found in streams vitb clear, cold water, in both riffles and pools vith
bottom types ranging from silt to gravel and. rock. Generally, it is
most abundant in cover such as coarse rock or thick srovths or wa~er
cress. The banded sculpin tolerates higher temperatures than the
mottled sculpin and is the more abundant of the tvo in larger and
va.""Dler ' streams. Sculpins live on the bottom, spending considerable
time ly,ing motionless in one spot and moving in short, quick dashes.
.... .555.. Rel:lroduction. The mottled sculpin spawns in the spring vhen
vater temperature reaches about l~C. The adhesive eggs are deposited
in clusters of about 200 on the undersides of stones. Tbe incubation
period is 3 to 4 veeks and the male remains near the nest until the
fry dispe!"se.
556. Food. Larval aquatic insects are the main diet of sculpins.
Cottids are predaceous, but they do not feed extensively on eggs and
young of trout, as is sometimes claimed (Pflieger 1975).
557. Arz.e and growth. The mottled sculpin is 28 to 36 mm lang
vhen one year old. It probably does not mature until its third or
fourth summer of life. Adults are commonly 60 to 90 mm long and the
1 54
.·
. ·
' .
·.
. . . _.
.... ,.
...
111&XiDru:m is about 115 mm. The banded scupli n is somewhat larger. Ad:ul t a
are co.aonly 65 to 130 mm long and the I:I&Ximum is 185 mm or more.
Sculpins i n tailvaters
558. Sculpins have not been extensively studied in tailvaters,
although they are numerous in s001e cold tailvaters. Pfitzer (1962)
noted that soulpins became important as forage in many cold tailvaters
of the Tennessee Valley whe.n the number of minnow species declined.
Both the banded sculpin and mottled sculpin have become numerous in
Chilhovee tailvater, Norris ta.ilvater, and Apalachia tailvater (Hill
1978). The mottled sculpi'n is the most abundant species in both the
Nor~ork and Bull Shoals tailwaters in Arkansas (Brown 1967; Hoffman and
ICilambi 1970). Sculpins are also abundant in the McKenzie River. System.
Oregon, vhere they are found in the cold tailvaters of four hydropower
fa.cilities and one flood-control dam (Hutchison et. al. 1966).
559. Cottids are not found in all tailwaters. The mottled
. sculpin has, disappeared below four hydropower dams on the Au Sabl e
River, Michigan (Richards 1976), and were rarely collected during 1966
studies in the cold Beaver tailwater, Arkansas (Brown 1967) .
560 . Sculpins are highly susceptible to stranding during lar.ge
water fluctuations because of their sedentary behavior. A total of 55
sculpins vere found ·stranded in three 0.82-m2 sections of the tailwater
below a Wyoming dam. It was recommended that flow dec.reases not exceed
2.8 m3 /sec/day , to allow for fish migration out of the area (Kroger
1973).
561. Overall, reductions in flow do· not appear to affect sculpin
survival. The piute sculpin (formerly eagle sculpin) is one of the·
surviving native species in the Granby Dam tailwater, Colorado, in
spite of large flow reductions.
562. Sculpins appear to reproduce suc cessfully in a number of
tailvaters . The banded sculpin vas the only fish speci es able to
revroduce in the cold Dale Hollov tailvater, Tennessee; no young of
the year other than sculpins were observed (Little 1967). The partial
inundation of a tailvater by a dovnstream reservoir beginning in about
155
1970 seriously reduced the abundance of the banded sculpin. and the
·' species is nov infrequently collected (Bauer 1976).
563. The food babi ts of sculpin& in tail:vaters are not well
known. The common bullhead, a cottid which occurs in Cov Green
tailvater on t .be 'l'ees River, United Kingdom, exhibited a feeding shift
following impoundment of the reservoir. The reduction of Plecoptera
caused the adults to begin feeding on mollusks • and t he fry shifted
to Diptera and Epbemeroptera (Crisp et al. 1978), The f~ ot the
banded sculpin in Dale Hollow t-ailvater, prior to inundat~ion by the
downstream Cordell Hull Reservoir, cons.isted of Diptera, Coleoptera,
Isopoda, c.rayfish, and small trout. The sculpin& did not eat Cladocera,.
vbich vere abundant in the reservoir discharge (Little 1967) •
. '
·. -·
156
. ·
~.· . -·"' . ..
: ·,·
. : .
PART VIII: CONCLUSIONS
564. The construction or an impoundment alters the biological,
chemical, and physical characteristics of the stream environment be,lov
the reservo·ir. Many or the biological changes are a direct result or
dam construction, and include blockage of upstream fish migration,
inundation of spawning grounds, and the interruption of downstream
invertebrate drift. In addition, the tailvater biota is influenced by
the characteristics of the impoundment and the f 'aunal and geomorphic
characteristics of the preimpoundment stream.
565. Physical and chemical characteristics in the tailwater are
primarily determined. by the volume and t i.ming of water released and by
the depth from vbich water is withdrawn from the reservoir. The effects
of these releases are further modified within the tailwater by inflows
from downstream tributaries and groundwater, riparian vegetation,
atmospheric conditions, and physica1 characterist.ics of the streambed.
The tailvater biota reflects interactions between the nati,ve or intro-
duced organisms and the physical and chemical cond.i tions .in t.he , -' -, '. ·;·:·';"'<,.
tailwater.
. . ~· ,. : .
• • • -. '•' ' : :~1'1. ....
Effects of HyP<?limnetic Release on Downstream Biota
566. The depth of the discharge is of primary importance in deter-
mining the tailwater environment below stratified reservoirs. The
release depth affects vater temperatures, dissolved gas concentrations,
nutrients, turbidity, and the presence of toxic concent.rations of some
dissolved substances in the tailwater. These factors have a profound
effect on the tailwater biota.
567. Maximum and average water temperatures are generally colder -----.in the tailwater below a hypolimnetic release ~serv~ir than in the
-~
unimpounded stream. The effects of these coldwater releases are similar -----
on both warmwater and coldwater streams but are more severe for the
. wa.rmvater streEW.S . The reduced wat er temperatures may fall bel ov t he
tolerance levels of c.ertain native species of invertebrates and fish.
157
Lowered water temperature can increase the competition between native
species and introducfl!d organisms adapted to the colder environment.
The result ma~ be the loss of some native species from the tailwater.
568. A change in the seasonal water tempe,rature pattern also
occurs in tailvaters. Water in hypoli.mnetic discharges is colder than
that in the unimpounded stream during the sUDIIler and warmer during, the
winter. Delays in spring warming because of cold hypolimnetic releases
may e.l ter the .. reproduction, hatching, emergence, and developnent of
many inve!"tebrates and fish. The altered tempe.rature· reg.i•es may
disrupt the life cycles of sCDe insect spedes and. cause t .hem to emerge
during the winter or prevent them t'rCD hatching in the spring. Some -fishes may not reproduce because the cold water disrupts their physio-
logical developnent and eliminates the temperature stimul.us to spawn.
Some may spawn several weeks late, retarding egg and larval ile.velopment.
The smaller young are subject to more intense interspecific competition
and reduced over-winter survival.
569. The temperature of cold tailwat.ers below bypolimnetic release
dams built on wa!"mVater s t reams eventual.l.y returns to ambient as waters
.·,· proce~d downstream. The biota in the downstream section closely re-..
sembles that in the natural unimpounded stream. A transitional zone
may exist between the cold tail water and. the varm dovnstream river that
may not be readily inhabited by ei'ther coldwater or varmvater organisms.
This transitional zone is often larger than the immediate• tailvater
(Hulsey 1959).
(
510. Hypolimnetic releases into coldva.ter streams generally do
mot have e. drastic effect on the stream biota. \ilater temperat.ures in
these tail waters generally remain vi thin the tolerance le·vels of the
coldwater organisms that inhabited the original stream. Temperatures
may sometices be reduced below the tolerance level of certain organisms
vhich may disappear from the iirDDediate tailvater. This si tuatitm may
also result in some redistribution of i nsects and fish. For example,
chironomids and simuliids have replaced most other insect specie:s, and
brook trout have replaced rainbow a .nd brown trout in some tailvaters.
158
: .. ... . . , ___ •;~··· ..
. r··
571. The volume of cold, hypolimnetic vater stored in the reser-
voir and the loss of daily tempe·rature :f'luc.tuations in the tailvater
atfects downstream biota. Some reservoirs lack sufficient sto·rage
capacity of cold, bypoli.mnetic vater to maintain coldwater releases
throughout the summ.er and f'e.ll.. Inadequate storage. capac.i ty may .result
in the change from a coldwater to a varmvater tailvater during the
latter part of the sUIIIIIier. This change significantly affects the
tailvater biota, since coldwater organisms cannot survive in the varm
vaters of late summer and ve.rmvate.r organisms cannot reproauce or grov
in the cold waters vhic!l occurred earlier in the year.
572. The loss of diurnal fluctuations in vater temperature .may
remove the temperature -stimulus necessary for normal progression of
invertebrate life processes. Some invertebrates may disappear but
other better adapted species usually replace them. Invertebr'ate popu-')
lations in these stressed environments often display lov diversi 't,ies I
and high densities.
573. Lov dissolved oxygen concentrations in tailvaters belov
St·ratified deep-release reservoirs may cause physiological Stress in
the aquatic coomrunity and limit fish and invert.ebrate diversity. Bio-
logical decomposition in the hypolimnion of some reservoirs during the
summer eliminates most of the dissolved oxygen and results in the re-
lease of deoxygenated vater. If insufficien·t reaeration occurs in the
outlet vorks, invertebrates may enter the drift and fish may actively
migrate downstream. In extreme cases, lack of adequate dissolved
oxygen has been responsible for the die-off of fish in tailvaters. In
most tailvaters, however, turbulent flow over riffles rapidly inc reases
the· dissolved oxyge.n concentration as the vater proceeds dovnstresm.
574. Nutrients vhic·h enter a reservoir may be used by the reser-
voir phytoplankton or may settle into the hypolimnion. The dissolved
nutrients vhich accumulate in the hypolimnion, either as a result of
the decomposition of organic matter or directly from the wa'~ershed, are
flushed into the tailwater during release of hypolimnet i c w~~c!r and may
enhance primary productivity in the tailvaters. The additional nut!"i-
ents may increase periphytic algal production in the tailvater and,
159
consequently, increase the numbers of invertebrates reeding on or
living in the algae.
575. Toxic levels of' reduced substances, including iron, manga-
nese, hydrogen sulfide, and anmonia, may be formed in the hypolimnion
of a reservoir during low oxygen conditions. It is possible for these
substances to be released into the tailvater at levels which may stress
both the invertebrate and fish populations.
576. Turbidity is usually reduced in tail waters belov deep-release
dams and organisms vhich are adapted to turbid waters may be at a
competitive disadvantage. For example, reduced turbidity favors trout
and other clear-water species over rough fish. In some instances,
however, turbid inflows move through the reservoir as a density current
and are released into the tailwater.
Effects of EPilimnetic Release on Downstream Biota
577. Reservoirs with epilimnetic releases are generally less . '
disruptive t'o tail water "!:liota than are those vi th bypolimnetic releases •
• <u• \
· ·· Warmvater str~ams are· subject to only minor temperature .~hanges as a
result of the construction of an epilimnetic .release reservoir. The
water temperature of the discharge is usually within the tolerance
limits of the native va.rmwater stre8ln species and does not affect their
survival. Add.:i.tionally, scme species of fish and invertebrates -may be
... transported out of the reservoir and added to the taflvater bi:9~a. Fish
common in the reservoir often predominate in the tailwater. EpiUmnetic
discharge from a dam built. on a coldwater stream usually has a higher
summer and autumn temperature than the original stream. The varmer
discharges may cause changes in the biota of the tailwater. Coldwater
species ( plecopterans and trout) may be eliminated by temperatures
exceeding thei.r tolerance levels. .E.levated temperatures also may allow
rough fish (carp and suckers) to outCOl'lPete ,many of the native or i.ntro-
duced species (trout).
578. Low dissolved oxygen concentrations rarely limit the biota
below surface-release reservoirs. High levels of photosynthesis in
160
...
~-. . '
•I
' .. -
the reservoir epilimnion, gas exchange during passage of water from
the reservoir, and downstream turbulent flow all increase concentra-
tions of dissolved oxygen in the tailvater. Toxic concentrations of
iron, manganese, and. hydrogen sulfide are rarely encountered since
these materials are products of anoxic conditions in the hypolimnion.
579. Spillway releases from high dams, particularly in years of
high fl.ov, can cause gas supersaturation in tailvaters and result in
mortality to fish and invertebrates. Lov dovnstream temperatures and
a laminar flow inhibits the dissipation of the dissolved gases back
to the atmosphere. Gas supersaturation has been noted in the tail-
vater belov a dam on a varmvater stream in the central United States,
but the problem is most common at high dams on the larger rivers of
· the Pacific Northwest. Nitrogen supersaturation and nitrogen em-
·.bolism generally do not occur at lowhead dams.
580. Epilimnetic discharges are generally low in dissolved
· nutrients, since particles (algae, suspended material) containing
......
or sorbing nutrients settle into the hypolimnion. This loss of
nutrientft result~ to ·~~duced' .primary produc~ivity i~ t .he immediate
tailwater. However, the export of insects, phytoplankton and zoo-
, ·:· ·· .. :~.\.,;.::-: .. ,
plankton from the reservoir often compensates for this reduction.
Tlie exported organisms are often used as food and may increase the
numbers of fish congregating below the dam. Many of the inverte-
brates. may flourish below surface-release reservoirs because of the
export or plankton and other suspended organic matter from the
reservoir.
-· ....
581. Many reservoir fish move into the tailwater either through
the turbines or over the spillway. Tailwater populations of shad, .
sunfishes, suckers , pikes, and some percids may be maintained through
export fram the reservoir. In addition, native stream fishes often
concentrate here, and consequently sport fishing in tailwaters is
sometimes excellent. Tailvater fisheries are most successful in spring
&nd early summer because of migrations related to spawning. Sustained
low flovs adversely affect fishing success.
161
..
Effe~ts of Water Release Patterns on Downstream Biota
582. The timing and volume of vater released from a dam may
severely limit or enhance the tailvater biot~:: Changes in the flow
patterns after dam construction include seasonally stabilized flows,
sustained high flows (vith reduced peak flows) during h~gh water ..... .,
periods, minimum flows during dry periods, and diel fluctuating flows
below hydropower facilities. The effect of these flow changes on the·
biota may, however, be masked by other factors such as temperature,
dissolved oxygen, and toxic levels of reduced substances.
583. ·The tailvaters below most nonhydropowe.r reservoirs ba.ve a
more stable annual flow regime than that in unimpounded streams. The
stabilized flows that result from both a reduction in the intensity or
floods and t :he maintenance of flows during low-water periods provide a
less variable habitat. Dense algal mats, often associated with stabi-
lized flows, may inhibit the production of some native invertebrate
species that prefer rock substrates. However, the additional habitat
and food supply provided by the algal mats generally attract nev inTer-
tebrate taxa.that become an important part of the topd web~ but species
feeding on allochthonous material become less abundant. Nesting'fishes
may reproduce more successfully in a stabilized tailwater. Stable
flows may, however, be detrimental to fish that require moderate· flov
variation to initiate spawning activities.
584. The effects of high flows (floods) in natural streams have
been described by several authors (Tarzwell 1938; Seegrist and Gard
1972; Ryck 1976). High flows in tailwaters are generally less intense
than in unaltered streams but are continued over a longer time. The
effects of high flows on tailwater fishes are partly dependent on the
tailwater physiography. If the tailwater has deep pools, sufficient
cov~r. or backwater areas for fish shelter, high flows are less detri-
mental to fish populations than if the tailvater has little physical
variability. High flows during the reproductive per.iod of fish can
scour the stream bottom and destroy the eggs and larvae and··reduce
162
.·
·.
.. ,._·. i:-"•• ... ...
.... ~····· .....
i.
. -····.
•• ! .
.. •.
.,
... ~ ~-
,, ....
reproductive success, especially in unsheltered areas. Increased
discharges may ca.use catastrophic drift of benthos, causing a sub-
stan,tial decrease in benthic standing crops. High flows can be bene-
ficial in some tailvaters as they flush sediment frcm the interstices
of the rubble substrate and supply food and oxygen "':.o benthic
invertebrates.
585. Fall dravdovn of flood control reservoirs increases flows
into the tail water. Thi s drawdovn usually occurs after reserroir de-
stratification, when fish and other organisms a r e more evenly distri-
buted vi thin the reservoir. Many young-of-the-year and older fish may
be lost from the reservoir during this time. causing an increased
abundance in the ta ~ ,_vaters. The effects of the increased flows on the
·· resident stream fi.shes in the tailvater, both during the rese!'"'roir
dravdovn and for sustained periods after flood flows, are largely
unknown •. The increased flows may initially produce catastrophic effects
on stream inverteb.rates, but t 'he ben'thic community gradually stabilizes
·.
as the remaining flow-tolerant species adjust to the prevailing condi-
tions ,' ·Higher flows extend the influence of the reservoir discharg~ '· .·.: ·
·downstream.
586. The subject of mini'mum flovs is one of the most videly
studied as.pects of regulated s treams. During the dry season of late
summer and fall, mi nimum flows are often maintained below dams to
provide aquatic habitat for the survival of invertebrates and fish .
The habitat that remains, however, is usually of dec.reased quality and
•; ., .. , .. ··· · ·· quantity. Reduced . .habitat inc·r eases interspec i fic competition. for
apace and food ·among fish and among invertebrates. Both groups experi-
ence physiological stress and reduced production during low flows .
...
~ flovs· in tailvaters reduce water velocities and associated detrital
material, and thus food and oxygen for benthic organisms are also
reduced . Lov flows allow silt and detritus to accumulate in the
t&ilvater frOD1 streamside rtmoff . This material may be beneficial to
the productivity i'n the tailvater if not present in excess i ve quanti-
ties. In coldwater streams, minimum flows from deep-release reservoirs
.·· ·•
often maintain vate.r temperatures vi thin tolerance levels for coldwater
species (e.g., trout.).
587. Irrigation storage reservoirs impound winter and spring
runoff, vith a consequent reduction in tailvater flo•vs. Winter de-
watering of the tailvater reduces overwinter survival of many organisms
by limiting habitat and exposins them to harsh winter conditions. Poor
survival of trout has been documented in streams devatered in winter.
Dewatering in the spring probably affects the reproduction of some
fishes by reducing both the stimulus to spawn and the availability of
.. spawning habitat.
588. Below hydropower dams, large diurnal·flow fluctuations most
often have a destructive influence on the tailwater biota and create an
unstable, highly variable downstream habitat. Tbe extreme variation in
flo,y SCO'.lrS the tailvater and displaces both fauna and flora. Species
vith narrowly defined envirorunental requirements are eliminated from
these tailwaters. During power generation, high water velocities cause
streambed and bank instability and habitat degradation. The stream may
.. be subject to increased. turbidity, and algal and macrophytic growth is
· discouraged. The widely fluctuating flaws discourage the establishment
of streamside vegetation and other aquatic plants .. The benthic !ood.
base is radically reduced and some. species may be e1iminated. A "zone
of fluctuation" is permanently establishe.d where no production takes
place because of periodic streambed exposure during nonpower cycles.
589 .. Fluctuating flows disrupt the spawning and reproductive
success of some fish species by destroying .nests and sweeping avay
unsheltered eggs and fry. Only fish adapted :to high vater velocities
are able to sustain their populations in tailvaters below hydropower
dams. Stranding and desiccation of many species of invertebrates, fish
eggs, salmonid fry, and sculpins have been ·reported,. Invertebrates
located in 1luctuating tailwaters may attain community equilibrium,
provided they are able to adapt to the vr.riati.ons in flow.
590. The release of large volumes ot cold bypolimnetic water
during power generation maintains a cold tailwater environment below
some southern reservoirs. However, during nongenerating periods, the
164
' .. ,.._ ... . '
• " \,o'', '" ....... :
small volume of water released may warm rapidly due to solar radiation
and exposure to warm. air temperatures. The thermal tolerance of some
tish and invertebrates may be exceeded during these periods, and the
organisms either move out of the tailwater or die. The increased water
temperatures may be beneficial to some species, such as carp and
smellmouth bass, that compete with coldwater fishes. Despite the fluc-
tuating flows encountered below hydropower dams, many excellent trout
tisher:ies have developed in these waters. The quality of the fishery
depends on the habitat suitability for trout, which includes cold water,
adequate flow, plentiful cover and food.
Past Tailwater Research and Suggestions for Future Study
591. .Review of the available literature revealed that the present
understanding of biological problems in tailwaters is far from complete.
CUrrent research being funded or conducted by various groups, including
the U. S. Army Corps of Engineers, Tennessee Valley Authority, U. S.
Water and Power Resources Service (formerly Bureau of Reclamation)~ and ·.·:·.:·.:
' • ,A._
the U. S. Fish and Wildlife Service, may provide the necessary infor-."' ;
mat.ion. to overcome the inadequacy of the literature.
592. Most tailwater research has been narrow in scope. Usual!y,
t .he study of the biota in a tail water has been l.im.i ted to the compila-
tion of lists of invertebrate species and fish species or creel census .
It has sometimes been assumed that a major change in one physical
factor (e.g., temperature, flow, etc.) has caused a change in the
tailwater biota. However, the more comprehensive investigations needed
to confirm these assumptions have rarely been conducted.
593. The fev studies that have been directed toward. determining
the causes for observed changes in tailwater biota have generally been
the result of acute short-term problems (e.g., fish kills cau~ed by
gas supersaturation or reduced dissolved oxygen). The mo ::-e subt].e
changes resulting in the disappearance of a species or change o:: spe-
~ies composition in tailwaters have general.ly not been dete"rmined. As
an example, the loss of a fish species in cold tailwaters has been
165
attributed to the reduction in temperature. What is usually not known
is whi c h stages of the fish's life cycle were affected by the lowered
temperature. Reduced temperatures may have had any of several effects
or combinations of effects: (a) prevented the initiation of spawning
activity, (b) inhibited the hatching of eggs, (c) impeded the growth of
fry, (d) destroyed a required food. source, (e) provided other species
with a competitive advantage, or {f) simply be.en below the tolerance
limits of the affected species. If the "weak link" in the life cycle
of the species was known, it might be possible to release water of a
more favorable temperature during the critical period (e.g., releasing
water of a wa_~er temperature until egg hatching is completed).
594. It is improbable that c'hanges in species composition were
due solely to one factor, such as a reduction in temperature. Changes
in the tailwater biota are more likely due to the alteration of a
number of factors such as temperature, flow, ha:bita.t·availability, food
abundance, and the levels of turbidity, dissolve.d gases, and certain
chemicals. Additionally, the degree to which these &l.terations . affect
· ·. ·, the''biota· in" each tail water may be highly variable. Th~ bi~t~ i~· 't¥o .'
., .. ~·t a,p·p~~ntly. s~~ilar tailwater~ may. "re~ct diffe~ntly t'o·i~i~ii~--~~~~5-
in chemical and physical factors because of differences in project
location, construction, and operation. Indeed, it is possible that in
some tailwaters the assumed cause of the faunal changes (e.g., t~per
ature ·redu~tion) may not have had any real effect, but simply masked
the actual causative factors.
595. Studies are needed to determin~ the tailwater chemical and
physical properties that cause changes in diversity and abundances in
the biotic community. Such studies should investigate all parts of
the tailwater ecosystem and must include continuous (i.e., daily)
monitoring of major chemical and physical variables and periodic
sampling of the tailwater biota (i.e., periphyton, plankton, benthos,
fish). Once sufficient information on the chemical and phy-sical
environment of a tailwater is obtained, it should be possible to relate
this information to observed changes in the biotic community with
appropriate statistical analyses.
166
~. ··-.;:~~·. ), -
•. . . .
..
......
.-..
•,
...
. . ~ .
596. In addition to determining which chemical and physical
factors act to alter the biotic community, further more intensive,
limited studies will be needed to di scover how these factors act on
the most seriously affected members of the biota. Only by determining
how the affected tailwater organisms are influ.enced will it be possible
to suggest improvements in the current tailwater management plan; for
example, how a valuable varmwater fish species is influenced below a
bypolimnetic release, hydropower dam. It may be determined that the
disappearance of this species is most closely correlated with diurnal
flow and tempe.rature fluctua·tions and delayed seasonal warming. More
narrow·ly defined studies may d etermine that fish spawning has been
delayed because of a lack of adequate thermal stimulus and that fish
egg hatching and invertebrate food production have declined because of
the periodic drying-of spawning beds and riffle areas ~ Ultimat~ly, it
will be up to the managing agency to determine if any of the suggestions
.. might be implemented within the context of an overall reservoir manage-
m~nt plan .
597. The type of intensive study just discussed is only useful for
understanding the problems of an individual tailvater being investi.gated .
It would be helpful in the· future to have a generalized conceptual model
of each major tailwater type. to assist in the recognition of tail~ter
problems without resorting to large-scale intensi-ve studies. Such a
conceptual model mu s t provide a clear understanding of how the major
chemical, physical, and biologi.cal variables relate to and interact
with each other.
· ... -· ... . ~ .. .. .....
.........
.. •
. ...
167
':
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structure of f 'our special lotic habitats in Colorado, U.S.A.
Verb. Int. Verein. Limnol. 20:1382-1387 ...
Ward, J. V., and J. A. Stanford. 1979. Ecological factors controlling
stream zoobenthos with emphasis on thermal modification of
regulated streams. Pages 35-56 in J. V. Ward and J. A. Stanford.,
'eds •. }'h~ Ec.ology of Regulated Streams. Plenum Press, Rev York.
·~_Warden, R. L., Jr.; and W. A. Hubert. 1977.
· ·•· · · Lepomis from the Wilson Dam tailvater.
179-183.
Spring stomach contents of
J. Ala; Acad. 'Sci. 48(4):
Waters;T. F.
drift.
1964. Recolonization of denuded stream bottom areas by
Trans. Am. Fish. Soc. 93(3):311-315.
Waters, T. F. 1969. Invertebrate drift -ecology and significance to
stream fishes. Pages 121-134 in T. G. Hortbcote, ed. Symposium
on Salmon and Trout in Streams-.-H. R. MacMillan Lectures in
Fisheries. Univ. B.C., Vancouver.
Waters, T. F. 1972. The drift of stream insects. Annu. Rev. Entomol.
17:253-272.
Weber, D. T. 1959. Effects of reduced stream flows ou the trout
fishery below Granby Dam, Colorado. M.S. thesis, Colo. State
Univ., Fort Collins. 149 pp.
Webster, J. R., E. F. Benfield, and J. Cairns, Jr. 1979. Model pre-
dictions of effects of impoundment on particulate organic matter
transport in a river system. Pages 339-364 in J. V. Ward and
J. A. Stanford, eds. The Ecology of Regulated Streams. Plenum
Press, New York.
Weitkamp, D. E., and M. Katz.
sat.ur.ation literature.
1980. A review of dissolved gas super-
Trans. Am. Fish. Soc. 109(6):659-702.
188
,. :•
Welch, E. B. 1961. Investigation of ~ish age and growth and food
abundance in Tiber Reservoir and t 'he river below. Mont. Fish
Game Dep., Fed. Aid Proj. F-5-R-10. 18 pp.
Wesche, T. A. 1974. Relationship of discharge reductions to available
trout habitat for recommending suitable stream flows. Water
Resour. Ser. 53. Water Resour. Res. In.st., Univ. Wyo., Laramie.
73 pp.
Wetzel, R. G. 1975. Limnology. W. B. Saunders Co., Philadelphia.
743 pp.
White, R. L. 1969. Evaluation of catchable rainbow trout fishery.
Tex. Parks Wildl. Dep., Fed. Aid Proj. F-2-R-16. 18 pp.
Whitford, L. A. 1960. The current ef'fect and growth of fresh-water
algae. Trans . .Am._Microsc. Soc. 79(3):302-309.
\ol"bit .ford, L. A. , and G. J. Schumacher. 1961. Effect of current en
mineral uptake and respiration by a fresh-water alga. Limnol.
Oceanogr. 6:423-425.
Williams, R. D., and R.· N. Winget. 1979. Macroinvertebrate response, to
flow manipulation in the Strawberry River, Utah (U.S.A.). Pages
365-376 in J. V. Ward and J. A. Stanford, eds. The Ecology o.f
Regulated Streams. Plenum Press, New York.
Wiltzius, w. J. 1978. Some factors hi.storically affecting the di-stri-
bution and abundance of fishes in the Gunnison River. ·Colo.····
Di.v. Wildl., Final· Report. 202 P.P·
Wirth, T. L., R. C. Dunst, P. D. Uttormark, and W. Hilsenhof.f. 1970.
Manipulati~n of reservoir waters for improved quality and fish
population response. Wis. Dep. Nat. Re·sour., Res. Rep. 62.
23 pp.
Wright, J. C. 1968. Effect of impoundments on productivity, water
chemistry, and heat budgets of rivers. Pages 188-199 in
Reservoir Fishery Resources SYlllposium. Sout'hern Div., .Am.
Fish. Soc.
Yang, C. T. 1971. Formation of ri.ffles and pools. Water Res our. Res.
7(6) :1567-1574.
Young, W. C., D. H. Kent, and B. G. Whiteside. 1976. The infiuen~e of
a deep storage reservoir on the species diversity of benthic
macroin.vertebrate commu."li ties of the Guadalupe River, T.exas.
Tex. J. Sci. 27(1):213-224.
189
.. . ·-
•,. 'It ~·
. . ~ . . .. . .. ··!"
.. . ....
..
. . ..
..
., \. ·•'· · .
. .,.1.
. :_
.APPEI.'lDIX A: ALPHABETICAL LIST OF THE 113 TAILWATERS MENTIONED .. ":. ,: .
. IN THE TEXT WITH LOCATION BY RIVER AND STATE, PROVINCE, OR COUI'l'RY
> 1\)
Antelope
Apalachin
Augusta
Barren
Deaver
Bennett
Berlin
Big Bend
Bliss
Blue Lake
Tail water
'Blue Mesa
Boulder (Hoover)
Boysen Unit
Broken Bow
Buckhorn
Bull Shoals
Caballo
Calderwood
Canton
Canyon
Cape Horn Diversion
Carl Blackwell
Carlyle
Center Hill
River
Jordan Creek
Hiwasse
Kennebec
Barren
White
Peace, Athabasca
Mahonlng
Missouri
Snake
Sawmill Creek
Gunnison
Colorado
Wind
Mountain Fork
Kentucky
White.
Rio Grande
Little Tennessee
North Canadian
Guadelupe
Eel
Stillwater Creek.
Kaskaskia
taney Fork
(Continued)
State(s), Province(s)
or Country
Oregon
Tennessee
.Maine.
Kentucky
Arkansas
Alberta, British Columbia
Ohio
South Dakota
Idaho
Alaska
Colorado
Nevada, Arizona
Wyoming
Oklahoma
Kentucky
Arkansas
New Mexico
Tennessee
Oklahoma
Texas
California
Oklahoma
Illinois
Tennessee
> w
Cherokee·
Chilhowee
Tailvater
C. J. Strike
Clark Canyon
Clearwater
Conowingo
Cooke
Cordell Hull
Cottage Grove
Cow Green ·
Coyote
Cumberland
Dale Hollow
Davis
Dexter
Diversion (unnamed)
Dorena
Douglas
East Lynn
Elephant Butte
Ennis
Fern Ridge
Five Channels
Flaming Gorge
Fontana
Fontenelle
Foote
Fort Randall
·.,
.· .
River
Holston
Little Tennessee
Snake
Beaverhead
'alack
Susquehanna
Au Sable
Cumberland
Coast Fork Willamet te
Tees
Russian
Cumberland
Obey
Colo·rad.o
Middle Fork Willamette
Blacktail Creek
Row
French Broad
Tveh•epol e Cr eek
Rio Grande
Madison
Long, Tom
Au Sable
Green
Little Tennessee
Green
Au Sable
M1ssouri
(Continued)
State(e), Province(s)
or Country
Tennessee
Tennessee
Idaho
Montana
Missouri
.Maryland
Michigan
Tennessee
Oregon
United Kingdom
California
Kentucky
Tennessee
Arizona, Nevada
Oregon
Montana
Oregon
Tennessee
West Vi rginia
New Mexico
Montana
Oregon
Michigan
Utah, Colorado
North Carolina
Wyoming
Michigan
South Dakota
Tail water
Glen Canyon
Granby
Hartwell
Hebgen
Hog Park
Holyoke
Hoover
Jackson Lak.e
Kentucky ·
Keystone
Kuibyshev
Lake of the Ozarks (Bagnell)
Lewis and Clark (Gavins Point)
Libby (Koocanusa)
Little Goose
Little Grassy
Lock and Dam 12
Lookout Point
Loramie
Low head (unnamed)
Lower Salmon Falls
McNary
Mingeshaur
Mio
Morrow Point
N~vskaya
·'·
j.-· .··:·.·~-
~.. !'I
'-.
River
Colorado ,
Colorado
Savannah ·
Madison
Hog Park Creek
Connecticut
Big Walnut Creek
Snake
Tennessee
Arkansas
Volga
Osage
Missouri.
Kootenai
Snake
Crab Orchard Creek
Mi.ssissippi
Middle Fork Willamette
Loramie.
Maquoketa ·
Snake
ColtDDbia ·
Kura
Au Sable ~' ~~·
Gunnison :
Narova
(Continued)
State(s), Province(s)
or Co\Ultry
Arizona
Colorado
Georgia, South Carolina
Montana
Wyoming
Massachusetts
Ohio
Wyoming
Kentucky
Oklahoma
U.S .S.R.
Missouri
Nebraska, South Dakota
Montana
Washington
Illinois
Illiqoi~, Iowa
Oregon ·
Ohio
Iowa
Idaho
Oregon, Washington
U.S.S.R.
Michigan
Colorado
U.S.S.R.
..
Tail water
Navajo
Nolin
Norfork
Norris
Oahe
Owyhee
Perc.ha Diversion
Pickvick.
PoDIIle de Terre
Roanoke Rapids
Rob Roy ·
Rocky Gorge (Triadelphia)
Rough
Shand
Shasta
South Holston
Stockto.n
SUJJIIIersvilJ.e
Table Rock
Taneycomo
Taylor Park
TenkUler
Tiber
Twin Valley
Upper Salmon Falls
Urievllle
•state owned pondu.
RiYer
San Juan
Nolin .'
North Fork
Cli.nch
Missouri
Owyhee
Rio Grande
Tennessee
Po11111e de Te.rre
Roanoke
.Douglas Creek
Patuxent
Rough
Grand
Sacramento
South Fork Holston
Sac
Ga.uley
White
White
Taylor
Illinois
Mari.as
Mill Creek
Snake •
(Continued)
State(s), Province(s)
or Country
New Mexico
Kentucky
Arkansas
Tennessee
South Dakota
Oregon
New Mexico
Tennessee
Missouri
North Carolina
Wyoming
Maryland
Kentucky
Ontario
California
Tennessee
Missouri.
West Virginia
Missouri
Missour.i
Colorado
Oklahoma
Montana
Wisconsin
Idaho
Maryland
> 0\
Vir
Volgograd
Watauga
Watts Bar
Wilson
Wister
Wye
Tail water
Wyman
Yellowtail
-state owned ponds.
•.
., .
Svratka
Volga
Watauga
Tennessee
Tennessee
Poteau •
Kennebec
Bighorn
.·
River
State(~). Province(s)
or Country
· C7.echoslovakia
U.S.S.R.
Tennessee
Tennessee
Alabwna
Oklahoma
Maryland
Maine
Monta:na
----~-------------------------------------------------------------------------------------------
... ·· APPENDIX B: ·LOCATION OF 105 RESERVOIR TAILWATERS .,
IN THE UNITED STATES MENTIONED IN THE TEXT
.....
6-1
~ .
.,
.... ~···
w
1\)
.. .. . "'-·
.": .
; .
Figure Bl
'
. •-.
. . · .
•
. APPENDIX C: . COMMJN AND SCIENTIFIC NAMES OF FISHES
MENTIONED IN THE TEXT • ARRANGED BY FAMILY
t-\
•' ....
' ..
. ; '
Part I: Fishes from North American Tailwaters
······ . Polyodont i dae · .
Paddlefish
Clupeidae
Skipjack herring
American shad
Gizzard shad
Th:::-eadfin shad
Salmonidae ..... -·
Coho salmon
Cutthroat trout
Rainbow trout
Brown trout
BTook trout
Esocida.e
Grass pickerel
Northern pike
Muskellunge
Chain pickerel
CyJ>rinidae
Chiselmouth
Stoneroller
Carp
Humpback chub
Bonytail
Roundtail chub
Speckled chub
Bigeye chub
Streamline chub
Peamouth
Hornyhead chub
River chub
Golden shiner
Texas shiner
Rosefin shiner
Emerald shiner
Polyodon spathula (Walbaum)
Alosa c sochloris (Rafinesque)
Alosa sanidissima Wilson)
no;;soma cepedianum (Lesueur)
Dorosom.a pete·nense (GUnther)
Oncorhynchus kisut.ch (Walbaum)
Salmo clarki Ri.chardson
~ gairdneri Richardson
Salmo trutta Linnaeus
~linus fontinalis (Mi tchill)
Esox americanus vermicul.atus
Esox lucius Linnaeus
Es·ox masouinone;y Mitchill
Esox niger Lesueur. , ... ,.,
Lesueur
Acrocheilus a1utaceus Agassiz·and ·
Pickering
Campostoma anomalum (Rafinesque)
Cyprinus carpio Linnaeus
Gila cypha Miller
Gila elegans Baird and Girard
Gila robusta Baird and Girard
HYbQpsis aestivalis (Girard)
Hybopsi s amblops ( Rafi.nesque)
Hybopsis dissimilis (Kirtland)
Mylo e heilus caurinus (Richardson)
Nocomi.s biguttat.us (Kirtland)
.Nocomis micropogon (Cope)
Notemigonus crysoleucas (Mitchill)
Notropis amabilis (Girard)
Notropis ardens (Cope)
Notropis atherinoides Rafinesque
(Continued)
C2
:•:.
•,_ .•.
;·. ·-;-.
,·
Cyprinidae (continued)
Bigeye shiner
Striped shiner
Common shiner
Whitetail shiner
Blackchin shiner
Spottail shiner
Red shiner
Silver shiner
Dusky!ftripe shiner
Rosyt'ace shiner
Spotfin shiner
Sand shiner
Teles~ope shiner
Redt'in shiner
Blacktail shiner
Mimic shiner
Suckermouth minnow
Southern redbelly dace
Bluntnose minnow
. Fathead minnow .
....... , . Bullhead minnow
: · · · Colorado · squaWrish
Northern squawfish
Blacknose dace ·
Longnose dace
Speckled dace
Redside shiner
. Creek chub
Catostomidae
River carpsucker
Quill back
Longnose sucker
White .sucker
Bluehead sucker
Flannelmouth sucker
Largescale sucker
Mountain sucker
Blue sucker ·. .
Northern hog sucker
SmalJ.mouth buffalo
Bigmouth buffalo
Black buffalo
.. ;
~. ~ .... ,J -••
Notropis boops Gilbert
Notropis ehrysocepbalus (Rafinesque)
Notr opis cornutus (Mitchill)
Notropis galacturus (Cope)
Notr opi s heterodon (Cope)
Notropis hudsonius (Clinton)
Notropis lutrensi s (.Baird and Girard)
Not ropis photogenis (Cope)
Notropi s pilsbryi Fowler
Notropis rubell us (Agassiz)
Notropis spilopterus (Cope)
Notropis stramineus (Cope)
Not roois t elescop1ls (Cope)
Notropis umbratili s (Girard}
Notroni s venustu s (Girard)
Notropis volucellus (Cope)
Phena c obius mira.bilis (Girard)
Phoxinus erythrogaster (Rafinesque)
Pime phales notatus (Ra.t'inesque)
Pimephales oromela.s Rafinesque
Pimepha.les vie;ilax (.Baird and Girard) :
Ptychacheilus lucius G~rard · -: :· · .;..; ·
Ptychocheilus oregonensis (Richardson)
Rbinichthys atratulus (Hermann) ·
.Rhinicbtbys cat a.ractae · (Valenciennes)
Rhi n i cht hys osc.ulus (Girard )
Ricbardson ius bal teat us (Richardson)
Semotilus atromaculatus (Mitchill)
Caryiodes carpio ( Ra.finesque) ·
Carpi odes cyprinus (Lesueur) ..
Catostomus catostomus (Forster)
Cat osto.mus commerson i (Lacepede)'
Cato stomus discobolus Cope
Catostomus latipinnis Baird and Gi rard
Catostomus m.acrocheilus Girard
Catos tomus olatyrbyn.chus (Cope)
Cyele;ptus elongatus {Lesueur)
Hypentel ium nigr.icans (Lesueur)
Ict.iobus bubalus (Rafi oesque)
Ictiobus . cypr'inellus (Valenciennes)
Ictiobus niger (Rafinesque)
(Cont i nued)
C3
Catostomidae (continued)
Spotted sucker
Silver redhorse
River redborse·
Gray redhorse
Black redhorse
Golden redhorse
Shorthead redhorse
Humpback sucker
Ictal uridae
White catfish
Blue catfish
Black bullhead
Yellow bullhead
Brown bullhead
Ch.annel catfish
Slender madtan
Sto·necat
Tadpole madtom
Brindled madtom
Freckled madtom
Flathead catfish
· Percichthyid&e
White bass
Yellow bass
Striped bass
Centrarchidae
Rock bass
Green sunfish
Ora.ngespotted sunfish
······'Bluegill
Longear sunfish
Redea:r sunfish
Smallmouth bass
Spotted bass
Largemouth bass
White crappie
Black crappie
Miny-trema melanops (Rafinesque)
Moxostoma anisurum (Rafinesque)
Moxos:toma. carina tum (Cope)
Moxostoma congestum { Bail1 and Girard)
M'oxostoma duouesnei (Lesueur)
Mox.ost.oma erythrurum {Rafinesque)
Moxostoma macrolepidotum (Lesueur)
Xyraucben texanus (Abbott)
Ictalurus catus (Linnaeus)
Ictalurus ~tus (Lesueur)
Ictalurus me~as (Rafinesque)
Ictalurus iiit8i'is {Lesueur)
Ictalurus nebulosus (Lesueur)
Ictalurus punctatus (Rafinesque)
Noturus exilis Nelson
Noturus flavus Rafinesque
Noturus e;:rrinus {Mitchill)
Not u:rus . miurus Jordan
Noturus nocturnus Jordan and Gilbert
Pylod.ictis olivaris (Rafineaque)
Moron.e chrysops (Rafi'nesque)
Morone mississippie·nsis Jordan. and
Eigenmann
Marone saxatilis (Walbaum)
Amblonlites rupestris {Rafinesque)
Lenomis cyanellus Rafinesque
Lepomis humilis (Girard)
.Lepomis macrochi rus Rafinesque
Lenomis megalotis (Rafinesque)
Leopmi s microlophus (Giinther)
Micropterus dolo~eui Lacepede
Micropterus punctulatus (Rafines que)
Micropt erus .s a lmoides (Lacepede)
Pomoxis annul.aris Rafinesque
Pomoxis nigroma c ulatus (Lesueur)
{Continued)
c4
. ...
Perc.idae
Greenside darter
Rainbow darter
Fantail darter
Johnny darter
Tessellated darter
Orangethroat darter
Banded darter
YelJ.ov perch
Logperch
Gilt darter
Blacks.ide darter
Sauger
Walleye
Sciaenidae
Freshwater drum
Cottidae
Mottled sculpin
Piute sculpin
.Banded sculpin
•• J ......•
Etheostoma blennioides Rafinesque
Etheostoma caeruleum Sto.rer
Etheostoma tlabel.lare Ra~inesque
Etheostoma n.igrum Rafinesque
Etheostoma ol.mstedi Storer
Etheostoma s ectabile ( A8assiz)
Eth.eostoma. zonale Cope )
Perea flavescens (Mitchill)
~na caprodes (Rafinesque )
Percina evides (Jordan and Copeland)
Percina maculata (Girard)
Stizosted.ion canadense (Smith)
Stizostedion vitreum. vitreum (Mitchill)
Aplodinotus grunniens Rafinesque
Cottus bairdi Girard
Cottus beldingi Eigenmann and
Eigenmann
Cottus carolinae (Gill)
C5
. ...... .
I
I ,,
Part II: Fishes from Europea.n Tail waters
Salmonidae
Baltic salmon
Cyprinidae
Zope
Bream
Golden shiner (European)
Bystr:ranka
Bl:eak
Barbel
White bream
Shemaia
Nase (Podust)
Carp
Gudgeon
Ide
Roach or Vobla
IChramulya
Vimba
Percidae
Volga pike-perch
Cottidae
Common bullhead (sculpin)
~ salar Linnaeus
Abramis bal~erus (Linnaeus)
Abramis ~ (Linnaeus)
Abramis sp.
Alburnoides bipunctatus (Bloch)
A1 burn us a1 bum us { Li nnaeus )
Barbus be:rbus (Linnaeus)
BUcca bjoerkna (Linnaeus)
Chalcalburnus chalcoides (~Uldenstadt)
Chondrostama nasus (Linnaeus)
Cyprinus caroio Linnaeus
~ gobio ~Linnaeus)
Leuciscus idus ( Linnaeus)
Rutilus rutuUs (Linnaeus)
Varicorhinus capoeta (~Uldenstadt)
Vi mba ~ ( Linna.eus)
Lucioperca volgensis (Gmelin)
Cottus gobio Linnaeus
C6
.I
·.
. ,·
.•.
APPENDIX D: LIFE HISTORY INFORMATION FOR THE
M:>ST COMK>N FISH GROUPS MENTIONED IN THE TEXT
:D-1
Fish group,
occurrence
Gizzard shad
Rivers, lakes,
and reservoirs;
most found
eastern U.S.
Trout
Rivera, lakes, and
reservoirs; common
throughout U.S.
Carp
Rivers, lakes, and
reservoirs; common
throughout U.S.
Suckers
Category
(forage, F;
game, G;
rough, R)
F
G
.R
Rivera, lakes, and
reservoirs; various
species round through-
out U.S.
R
'·
Table Dl -Fish Groups, General Characteristics
Life
span
years
4-6
3-5
5-6
5-6
First
Age
years
2-3
2-4
.;
2-4
maturit;y:
Length
nn Habitat
250-350 Pools,
backwaters
250-380 Riffles,
pools
300-450 Backwater
pools
300-400 Pools and·
riffles
(Continued)
0 ~
Pre terence's
Temperat'ure oc
22-24
10-15
20-22
14-20
.,
Water
clarlt;y:
No
preference
Clear
:Turbid
Clear to
. turbid
'• '
(Sheet 1 or 3)
t1 w
. .
Category
(forage, F;
Fish group, game, G;
occurrence rough, R)
Channei catfish
Most common in G
large rivers but
also found in some
reservoirs; intro-
duced throughout
the U.S.
White bass
Lakes, rivers, and G
reservoirs; intro-
duced throughout
the U.S.
Black basses*
Found throughout G
the U.S . in lakes,
reservoirs, and
rivers
:;· .
J. :-. \
0 •
' Table Dl (Continued)
Life First maturit;y:
span Age Length
years . ;y:ears IIDil ---
6-10 4-6 330-560
4-6 2-3 250-300
4-7 3-4 250-320
(Continued)
•
Preferences
Teaperature Vater
Habitat oc clarit;y:
Deep pools 27-30 Semi turbid
Deep pools 23-25 Clear
Pools 21-27 Clear
*Three species are c~mmon--largemouth,'smallmoutt.~ and spotted--and eac~ has different requirements.
.· (Sheet 2 of 3)
Table Dl (Continued)
Category
(forage, F; Life First maturitz PreJ:erences
Fish group, game, G· , span Age Length Temperature · Water
occurrence rO!!ejh 1 R) zears , zears nun llabi tat oc clarity
Sunfishes
Lakes, rivers, and F,G 3-4 2-3 100-150 Pools 22-25 Clear to
reservoirs; m.ost turbid
common eastern
two-thir ds U.S .
Crappies
Lakes, rivers, and F,G 3-4 2-3 150-200 Pools 22-24 Clear t o
res ervoirs; most slightly
t;l .e:-common easter n turbid
half U.S.
Walleze
Lakes, rivers, and G 5-7 3-4 350-450 Open water, 18-21 Clear
reservoirs; most pools
COftlllon eastern
half U.S.
(Sheet 3 of 3)
(
Fish sroup
Gizzard shad
Trout
d
VI
Carp
Suckers
Table
Fish Groups, Spawning and
Spawning
Season
Spring,
early
Winter,
spring
Spring,
early
summer
Late
winter,
spring
Temperature oc
17-?3
4-16
17-20
13-23
Location
Shallow,
protected
areas
(scattered)
Riffle
(nest)
Flooded
shallows
(scattered)
Shoal areas
(scattered)
D2
Eating Characteristics
IncUbation
period
dazs
4
20-Bo
4-8
4-14
Food
Youna Adults
Plankton Pl ankton
Plankton Insects,
fish
Plankton Insects,
plant
material
Plankton Insects,
algae
(Continued)
.
..
f:
•
Remarks
Young ooDJDon in
taflwaters dur-
ing fall and
winter; impor-
tant forage.
The rainbow is
the most common
trout stocked in
cold tallvaters.
Adaptable to·
many habitats;
considered a
nuisance because
of destruct! ve
habits.
About 12 species
ot suckers, in-
cluding redhorse
s uckers, occur
in tailwaters;
11 fe history
varies by
species.
(Sheet 1 o~ 3)
.
Table D2 (Continued)
SP,!vnins
Incubation
Temperature period Food
Fish sroul2 Season oc Location dals Youns Adults Remarks
Channel catfish Late 24-29 Natural 5-10 Plankton, Insects, Highly sought as
spring, cava ties insects fish food fish,
early (nest) particularly
swrmer southeastern
u.s.
White bass Spring, 14-21 Midwater 2 Plankton Insects, Important tail-
early over hard. .fi.sh vater sport fish
swmner bottom .. in spring and
8'-. ( scatte.red) summer.
Black basses Spring, 16-18 Sand-2-4 Plankton, Insects, Important aport
early gravel insects fish fish. Small-
summer (nest) mouth and
spotte.d basses
most common in
streams; large-
mouth in lakes.
Sunfishes Spring, 20-22 Firm 3-5 Plankton Insects Important sport
early bottom fi.shes. Blue-
summer (nest) gill , green and
longear sun-
fishes most com-
mon in tailvaters.
,'(f
(Continued) (Shee·t 2 or 3)
Fish group Season
Crappies Spring
Walleye Spring
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Table D2 {Continued)
Spawning
Temperature oc
6-8
Locat·ion
Firm
bottom
(nest)
Gravel,
rubble
(scattered)
Incubation
period
days
3
12-18
Food
Young Adults
Plankt.on • Insects •
insects fish
Plankton, Fiah
insects
• •
Remarks
Important sport
fishes. Adults
may be common in
tailvaters dur-
ing spring and
young during
fall and winter.
Important sport
f:lsb in tail-
waters of some
large rivers.
(Sheet 3 of 3)
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: .. -!· '· .~' ,· ... ,r.;. _:! .. ·: ·.: '.t· ......... .,. . APPENDIX E: ··. GLOSSARY .,JI•
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Algae: primitive plants, one-celled to many-celled.
Alloc.hthonous: materials such as leaves and detritus that originate
from outside a l~e or stream.
Amphipods: group of crustaceans that includes the freshwater forms
Hyalella and Gammarus.
Anadromous fish: fish that spend most of their lives in the sea or
lakes but ascend rivers to spawn.
Anaerobic organisms: microorganisms that thrive in the absence of
oxygen.
Annelids : earthworms and leeches .
Anoxia: state of having too little oxygen in tissues for normal
met.abol:!.sm.
Arachnids : spiders and water mites.
Armoring: acctDDulation of coarse particles on a stream bottom through
loss of finer materials to the current; the formation of a firm
layer on the streambed that is resistant to further degradation.
Arthropods: group of invertebrate animals that 'includes . crustaceans,
insects, and spiders.
Autochthonous: materials such as algae, macrophytes, and their decom-
posi t .ion products that originate vi thin a lake or stream.
Auto~ropby: type of nutrition in which an organism manufactures its
own· food from inorganic compounds.
Benthic org~isms (benthos):
immature aquatic insects,
stream bottom.
aquatic invertebrates such as mollusks,.
and crustaceans that live on or in the
Biomass: total weight of a particular species or of all organisms in
a particular· habitat.
Biota: all living organisms in a region.
Bryozoans: small bottom organisms that make up part of the benthos.
Carnivore: any animal partly or wholly dependent on catching other
animals for its 'food.
Chironomids: family of insec~s of the Order Diptera; large group that
includes the non biting, mosqui tolike midges.
Cladocerans: freshwater crustaceans; includes such zooplankton genera
as Daphnia, Chydorus, and Alona.
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Copepoda: freshwater crustaceans; includes such zooplankton genera as
Diaptomus and, Cyclops.
Crustaceans: includes certain zooplankters (copepods and cladocerans),
ampbi,pods, dec a pods, 1 sopods , and, ostracods.
Daphnids: any member or the cladoceran genus Daphnia.
'Oecapods: freshwater shrimp and crayfish .
Detritivores: organisms 'that ingest detritus •
. Detritus: fine particulate debris or organic or inorganic origin.
Diatoms: class or r:a.lgae having silicified skeletons.
Dipterans: order of insects that includes true flies.
Drift: . aquatic or terrestrial invertebrates that move or float with ··
the current.
Ecology: science or the interrelations between living organisms and
the.ir environment.
Encystment.: formation of a resi·stant cyst by c.ertain microorganisms,
especially under un.!avorable environmental conditions.
Ephemeropterans: order or insects that .inc~udes the mayflies.
Epilimnion: upper stratum of more or less uniformly warm circulating
water that forms in lakes a.nd reservoirs during periods or stratifi-
cation and extends from the surface to the metalimnion or thermocline.
Excystment: portion of the life cycle of an organism when it e111erges
from its cyst stage and resumes normal. metabolic activity.
Fingerling: immature fish, from a length or about 25 mm (or size at
disap,pearance of yolk sac) to the end of first year of life.
Fry: life stage· or fish between hatching o'f the egg and assumption of
adult c.b&racteristics (usually at a length or about 25 DID).
Gastropods: snails.
. Habitat:
Herbivore:
place where a particular plant or animal lives .
organism that feeds on plant material.
Heterotrophy: type of nutrition in which an organism depends on organic
matter for food. -......
·.Hydraulic residence time: time (usually days) required for a volume of ·
vater equal to the reservoir capacity to move. through 'the reservoir
'and. be discharged downstream.
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Hypolimnion : lover stratum of cold and relatively undisturbed vater
that forms in lakes and reservoirs during periods of stratification
and extends from the bottom up to the metalimnion or thermocline.
Instar: any one of the successive stages in the life history of an
insect.
Isopods: freshvater c.rustaceans (.Asellus), vhich are similar to
terrestrial sow bugs.
Laminar flow: smooth, low-velocity flow, vith parallel layers of water
shearing over one another, and vi th li.ttle or no mixing of layers.
Lentic: standing vaters such as lakes an.d ponds.
Lepidopterans: order of insects that includes the moths and butter-
flies.
Limnology: study of the physical, chemical, and biological conditions
in fresh vaters.
Lotic: running waters such as streams and rivers.
Macrophytes: macroscopic or large forms of vegetation.
Metalimnion: stratum betveen the epilimn·ion and the hypolimnion in
stratified lakes and reservoirs; exhibits marked thermal discon-
tinuity; temperature changes at least 1°C per metre throughout
this .stratum.
-Mollusks: soft-bodied animals usually enclosed in a shell and having
a muscular foot; freshwater forms include snails and clams.
Nymphs: one of a serie.s of immature stages in certain insects .
Oligochaetes: earthworms and their aquatic representatives.
Om.."livore: any animal that eats a variety of living and dead plants
and animals.
Ostracods: small crustaceans enclosed in bivalve shells; resemble
small clams.
Periphyton·: ~:~.ssociation of aquatic organisms attached or clinging to
stems and leaves of rooted plants or other surfaces projecting
above the stream bottom.
pH: the negative logarithm of the effective hydrogen-ion concentration .
Used to express both acidity and basicity on a scale of 0 to 14; 1
represents neutrality, numbers less than 1 increasing acidity, and
numbers greater than 1 increasing basicity.
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Photosynthesis: complex of processes involved in the . formation of
carbohydrates from carbon dioxide and water in living plants in
the presence of light and chlorophyll.
Phytoplankton: small plants (algae) that live unattached in the water.
Piscivorous: feeding on fishes.
Plankton: organisms. of relatively small size, mostl y microscopic,
that drift with the water current; some have vea.k powers of
locomotion.
Plecopterans : order of insects that includes the .stoneflies and
salmonflies.
Pool: portion of a stream that is dee·p and quiet relative to the main
current .•
Redd: type of fish spawning area (usually a cleared circular or oblo.ng
depression) in running wat er with a gravel bottom.
Redox potential: oxidation-reduction potential; a m~asure of the
. · oxidizing or reducing intensity of a solution.
Riffle: shallow rapids in an open stream, where the water surface is
broken into waves by obstructions wholly or partly submerged.
Run : stretch of relatively deep, fast-flowing water with the surface
essentially nonturbulent.
' Seston: :· living or nonliTing bodies of plants or animals that float ·or
. swim ·in tbe .water. ·
. Simuliids: family of insects of the Orde.r Diptera; includes black
flies and buffalo gnats .
Spate: a sudden freshet or flood.
Stenothermal: refers to an. organism that can maintain itself only
· over a relatively narrov range of temperature.
Strati~ication : separation of and nonmixing between the s urface
ep1limnetic water and the deep bypolU!znetic water because of
density differences between the tva layers •
Tail.Ma ter: channel o r stream below a dam.
Thermocline : see metalimnion .
·· Trichopterans : order of insects that includes caddis fli e s.
Trophic level : refers to the position occupied by an organism in a
simplified food c.hain •
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Turbellarians: free-11 ving flatworms.
Turbidity: cloudiness of water caused by the presence of suspended
matter.··
Turbulent flov: flov vi th secondary, heterogeneous eddies supe:r-
i=POsed on the main forward flow, accompanied by considerable
mixing of components.
Water quality: a term used to describe the chemical, physical, and
biological characteristics of water in respect to its suitability
for a pa-rticular use. ·
Zooplankton: animal microorganisms that 11 ve \Ulattached in the water •
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