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SUSITNA HYDRO AQUATIC STUDIES
PHASE II REPORT
Synopsis of the 1982
Aquatic Studies and Analysis of
Fish and Habitat Relationships
•I,•I•••
••••
SUSITNA HYDRO AQUATIC STUDIES
PHASE II REPORT
Synopsis of the 1982
Aquatic Studies and Analysis of
Fish and Habitat Relationships
by
ALASKA DEPARTMENT OF FISH AND GAME
Susitna Hydro Aquatic Studies
2207 Spenard Road
Anchorage, Alaska 99503
1983
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PREFACE
This report is a synopsis of the fisheries,aquatic habitat,and
instream flow data collected by the Alaska Department of Fish and Game
(ADF&G)Susitna Hydroelectric (Su Hydro)Feasibility Aquatic Studies
Program duri ng the 1981-82 (October-May)ice-covered and 1982
(May-October)open water seasons.It is one of a series of reports
prepared for the Alaska Power Authority (APA)by the ADF&G and other
contractors to evaluate the feasibility of the proposed Susitna
Hydroelectric Project.
In addition to the synopsis,this report also includes the analysis of
the pre-project fish and habitat relationships derived from Volumes Two
through Five (ADF&G 1983a,1983b,1983c,1983d)and related reports
prepared by other study participants.The topics discussed in Volumes
Two through Five are illustrated in Figure A.
These and other ADF&G reports (1974,1976,1977, 1978, 1979,1981a,b,
c,d,e,f,1982)and information reported by others will be summarized
and analyzed by the Arctic Env"ironmental Information and Data Center
(AEIDC)to evaluate post-project conditions within the overall study
area of the proposed project (Figure B).Woodward Clyde Consultants
will,in turn,use this information to support the preparation of the
Federal Energy Regulatory Commission License Application.
The five year (Acres 1980)ADF&G Su Hydro Aquatic Studies program 'lIas
initiated in November 1980.It is subdivided into three study sections:
FactorsInfluencingAquaticHabitatFishLifePhasesInfIuencedbyHabitatSpawningVal.3,Vol.!IRea,ln;Vol.3,Vol.4,Vol.!lOI,t,1butIonVol.3,Vol.4.VOI.!lIFOodHobits\Vol.3~Outmlg,atian~Vol.3-----Rive,Mo,phologyVol.4,Vol.!IChemicalVOl.4,Vol.!IFigureA.IntregrationofandrelationshipsamongprogramelementspresentedinVolumesIIthroughIV.
tADF8GFIELDCAMPSOVERALLSTUDYAREA•,,"......................................",,\\,IIII,I0'I//--_....-"o25IImiles••......16............Figure8.0verallstudvareaelftheSusitnaHydr("lp.lectt~irFeasibilitvStudyPi'oqram.
Adult Anadromous Fi sh Studi es (AA),Resi dent and Juvenil e Anadromous
Fish Studies (RJ),and Aquatic Habitat and Instream Flow Studies (AH).
Specific objectives of the three sections are:
1.AA -determine the seasonal distribution and relative abun-
dance of adult anadromous fish populations produced within the
study area (Figure B);
2.RJ -determine the seasonal distribution and relative abun-
dance of selected resident and juvenile anadromous fish
populations within the study area;and
3.AH characterize the seasonal habitat requirements of
selected anadromous and resident fish species within the study
area and the relationship between the availabil ity of these
habitat conditions and the mainstem discharge of the Susitna
River.
The 1981-82 ice-covered and 1982 open-water ADF&G study areas (Figures C
and D)were limited to the mainstem Susitna River,associated sloughs
and side channels,and the mouths of major tributaries.Portions of
tributaries which will be inundated by the proposed Watana and Devil
Canyon reservoirs were also evaluated.Descriptions of study sites are
presented in each of these volumes including the ADF&G reports (ADF&G
1981 a,b,c,d,e,f).
i v
~11982OPENWATERSEASONSTUDYAREASfffi1UPPERRIVERtmSTUDYAREA~LOWERRIVER~STUDYAREA--DRAINAGEBOUNDARYI,'!,,""I/"//,,'"...."oo25I,miles........."t:J<FigureC.1982ADF~Gnpenwaterseason(MaythroughOctober)studyarea.
LOWERRIVERSTUDYAREAUPPERRIVERSTUDYAREADRAINAGEBOUNDARY1981-82ICE-COVEREDSEASONSTUDYAREASfito,,".........................................\\,IIIIIIIoj/.,.,,/....._........-""II"////III/////.,.,,/----------(1\\o:::.IIIIIII\..............."..........""'.........."o25,lImiles1:)"0.1)o."C't?<-J.F;OL!reD~]c)8-t-F',:t/;F~~~~;~ce-co\Jeredse·~~CPl(Oc"~(lhrr-t:hrCill'.lr;r-·!i2VIstud'arE:.~.
Questions concerning these reports should be directed to:
Thomas W.Trent
Aquatic Studies Coordinator
Alaska Department of Fish &Game
Su Hydro Aquatic Studies Program
2207 Spenard Road
Anchorage,Alaska 99503
Telephone (907)274-7583
vii
PREFACE REFERENCES
Acres American,Inc.(Acres)1980.Susitna Hydroelectric Project Plan
of Study.Prepared for the Alaska Power Authority.Anchorage,
Alaska.
Alaska Department of Fi sh and Game (AOF&G).1974.An assessment of the
anadromous fi sh popul at ions in the Upper Sus itna River Waters hed
between Devil Canyon and the Chulitna River.Anchorage,Alaska.
__1976.Fi sh and Wi 1dl ife studi es related to the Corps of
Engineers Devi 1 Canyon,Watana Reservoi r Hydroel ectri c Project.
ADF&G.Anchorage,Alaska .
.1977.Preauthorization assessment of the proposed Susitna
Hydroe 1ec tri c P,rojects:pre 1 irni na ry i nvesti gati ons of water
quality and aquatic species composition.ADF&G.Anchorage,
Alaska.
___1978.Preliminary environmental assessment of hydroelectric
development on the Susitna River.Anchorage,Alaska.
_____1979.Pr'eliminary final
proposed by the ADF&G. ADF&G.
viii
plan of study fish and studies
Anchorage,Alaska.
-,
-
1981a.Aquatic studies procedures manual.Phase 1.Final
Draft.Subtask 7.10.Prepared for Acres Ameri can,Incorporated,
by the Alaska Department of Fish and GamejSu Hydro.Anchorage,
Alaska.
1981b.Adult anadromous fi sheri es project.Phase 1.Fi na 1
Draft.Subtask 7.10.Prepared for Acres American,Incorporated.
by the Alaska Department of Fi sh and GamejSu Hydro.Anchorage.
Alaska.
1981(;.Aquatic habitat and i nstream flow project.Phase I.
Final Draft.Prepared for Acres American,Incorporated.by the
Alaska Department of Fish and GamejSu Hydro.Anchorage,Alaska.
1981d.Resident fish investigation on the lower Susitna River.
Phase 1.Fi na 1 Draft.Prepared for Acres Ameri can,Incorporated
by Alaska Department of Fish and GamejSu Hydro.Anchorage,Alaska.
1981e.Resident fish investigations on the lower Susitna
River.Phase 1.Final Draft.ADF&G Su Hydro Aquatic Studies
Program.Anchorage,Alaska.
1981f.Resident fish investigations on the upper Susitna
River.Phase 1.Final Draft.ADF&G Su Hydro Aquatic Studies
Program.Anchorage,Alaska.
ix
1982.Aquatic Studies Program.Phase I.Final Draft.
Subtask 7.10.Prepared for Acres American,Incorporated by the
Alaska Department of Fish and Game/Su Hydro.Anchorage,Alaska.
1983a.Adult anadromous fish studies,1982.
II Final Report.ADF&G Su Hydro Aquatic
Anchorage,Alaska.
Volume 2 of Phase
Studi es Program,
1983b.Resident and juvenile anadromous fish studies on the
Susitna River below Devil Canyon,1982.Volume 3 of Phase II Basic
Data Report.ADF&G Su Hydro Aquati c Studies Program.Anchorage,
Alaska.
1983c.Aquatic habitat and instream flow studies,1982.
Volume 4 of Phase II Basic Data Report.ADF&G Su Hydro Aquatic
Studies Program.Anchorage,Alaska.
1983d.Upper Susitna River impoundment studies,1982.Volume
5 of Phase II Basic Data Report.ADF&G Su Hydro Aquatic Studies
Program.An~horage,Alaska.
x
TABLE OF CONTENTS
PREFACE "".. .. .. .. ...... ........ ........ .. .. .... ..i
LIST OF FIGURES ,xxii
LIST OF TABLES .....••..•........•.............................'"xxiv
_.1.
2.
I NTRODUCT ION ..
1.1 Purpose of report .
1.2 Study objectives ................•.•.....................
1.3 Utility of the report in impact analysis and
mitigation planning .
RESULTS AND DISCUSSION OF THE FISH AND HABITAT STUDIES
ON THE SUSITNA RIVER BELOW DEVIL CANyON .
1
1
1
2
2
a
2.1 Chinook salmon ".....................................Il
2.1.1 Adult phase of life cycle .4
2.1.1.1 Adult harvest by sport,
commercial,and subsistence
fi she ries ,.G
2.1.1.2 Adult escapement....................8
2.1.1.3 Habitat and environmental
parameters associated with the
adult phase of the life cycle
(upstream migration,passage,
spawning)..10
,
2.1.1.3.1 Discharge,water quality,
and temperature relation-
ships with the adult salmon
migration................Ie
2.1.1.3.2 Other factors that
influence the spawning
success of chinook
salmon...................14
2.1.2 Juvenile rearing and migration phases...........15
2.1.2.1 Relative abundance of juvenile
chinook salmon.........]5
xi
----------,---~..,._---------
TABLE OF CONTENTS (Continued)
2.1.2.2 Habitat and environmental factors
associated with the juvenile
phase of the life cycle.................20
2.1.2.2.1 Physical habitat
conditions of rearing
juveniles.....................21
Discharge (velocity and
depth)relationships
and their effects on
indices of available
habitat.......................21
Water quality and
thermal relationship 23
2.1.2.2.2 Timing of outmigration
from the tributaries t
sloughs,and mainstem
and its relationship
to environmental
changes.......................24
2.1.2.2.3 Food supply for rearing
juveniles and its
relationship to other
parameters and preference
dependency of species in
the sys tern.. . . . . . . . . . . . . . . . . . .26
2.1.2.2.4 Other physical and bio-
logical constraints...........27
2.2 Coho salmon............................................28
2.2.1 Adult phase of life cycle .28
2.2.1.1 Adult harvest by sport and
commercial fisheries 28
2.2.1.2 Adult escapement...................31
2.2.1.3 Habitat and environmental
parameters associated with the
adult phase of the life cycle......31
xii
TABLE OF CONTENTS (Continued)
2.2.1.3.1 Discharge,water
quality,and temperature
relationships with the
adult salmon migration........33
2.2.1.3.2 Other factors that in-
fluence the spawning
success of coho salmon........3~
.....2.2.2 Juvenile rearing and migration phases .35
2.2.2.1 Relative abundance of juvenile
coho sa lmon.. . .. . . •. . •. . . . . . . . . . . . .36
2.2.2.2 Habitat and environmental factors
associated with the juvenile phase
of the life cycle..............•...38
2.2.2.2.1 Physical habitat
conditions of rearing
juveniles................39
Discharge (velocity and
depth)relationships
and their effects on
indices of available
habitat..................39
Water quality and
thermal relationships....40
2.2.2.2.2 Timing of outmigration
from the tributaries,
sloughs,and mainstem
and its relationship
to environmental
changes..................41
2.2.2.2.3 Food supply for rearing
juveniles and its
relationship to other
parameters and preference
dependency of species in
the system...............42
-2.2.2.2.4 Other physical and bio-
logical constraints ..•...43
2.3 Sockeye sa 1man.. . . . . . .. . . . . . .. . . . ••. . . . . . . •. . . . . . . . •. . .44
2.3.1 Adult phase of life cycle.......................44
xiii
TABLE OF CONTENTS (Continued)
2.3.1.1 Adult harvest by sport and
commercial fisheries...............44
2.3.1.2 Adult escapement...................41
2.3.1.3 Habitat and environmental
parameters associated with the
adult phase of the life cycle
(upstream migration,passage
and spawni n9).. ..... .. .. . . .... .. . . .47
2.3.1.3.1 Discharge,water
quality,and temperature
relationships with
adult sockeye salmon
migration................49
2.3.1.3.2 Substrate type associated
with spawning............50
2.3.1.3.3 Other physical and bio-
logical constraints on
spawning success.........51
2.3.2 Incubation and emergence phase of life cycle....52
2.3.3 Juvenile rearing and migration phases...........53
2.3.3.1 Relative abundance of juvenile
sockeye salmon..........................53
2.3.3.2 Habitat and environmental factors
associated with the juvenile phase
of the life cycle..56
2.3.3.2.1 Physical habitat
conditions of rearing
juveniles .56
Discharge (velocity and
depth)relationships
and their effects on
indices of available
habi tat... .. . . .. .... .... .57
Water quality and
thermal relationship.....Sf
2.3.3.2.2 Timing of outmigration
from the tributaries,
sloughs,and mainstem
and its relationship
to environmental
changes ..............•........
xiv
59
TABLE OF CONTENTS (Continued)~~
2.3.3.2.3 Food supply for rearing
juveniles .•..•.•.........•....60
2.3.3.2.4 Predation and cover
relationships ...•............60
2.4 Chum salmon............................................61
2.4.1 Adult phase of life cycle •...................61
2.4.1.1 Adult harvest by sport and
commercial fisheries...............61
2.4.1.2 Adult escapement...................64
2.4.1.3 Habitat and environmental
parameters associated with the
adult phase of the life cycle
(upstream mi9ration,passage
and spawning)......................64
-
2.4.1.3.1 Discharge,water
quality,and tempera-
ture relationships
with the adult chum
salmon migration .66
2.4.1.3.2 Substrate type associated
with spawning............68
2.4.1.3.3 Other physical and bio-
logical constraints on
spawning success 69
2.4.2
2.4.3
Incubation and emergence phase of
1ife cyc 1e •...........•....•....•...••.•.....
Juvenile rearing and migration phases .
69
70
-
2.4.3.1
2.4.3.2
Relative abundance of juvenile
chum salmon ...............•.•......
Habitat and environmental factors
associated with the juvenile phase
of the life cycle ............•.....
2.4.3.2.1 Physical habitat
conditions of rearing
juveniles ....•...........
xv
70
71
73
...,.----~.~~~--=========
TABLE OF CONTENTS (Continued)Page
Discharge (velocity and
depth)relationships
and their effects on
indices of available
habi tat.. . . . . . .... . . . . . . .73
Water quality and
thermal relationships....74
2.4.3.2.2 Timing of outmigration
from the tributaries,
sloughs,and mainstem
and its relationship
to environmental
changes.. . . . . . . . . . .... .... . . . .75
2.4.3.2.3 Food supply for rearing
juveniles and its relation-
ship to other parameters
and preference dependency
of species in the system......76
2.4.3.2.4 Predation and cover
relationships.................76
2•5 Pin k sal mo n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
2.5.1 Adult phase of life cycle .77
84
2.5.2
2.5.1.1 Adult harvest by sport and
commercial fisheries...............77
2.5.1.2 Adult escapement...................80
2.5.1.3 Habitat and environmental
parameters associated with the
adult phase of the life cycle......82
2.5.1.3.1 Discharge,water
quality,and tempera-
ture relationships
with the adult salmon
migration................82
Incubation and emergence phase of
1i fe eye 1e .".".
2.5.3 Juvenile rearing and migration phase~.
xvi
85
TABLE OF CONTENTS (Continued)
2.5.3.1 Timing of outmigration from the
tributaries t sloughs t and mainstem
and its relationship to environ-
mental changes.....................85
2.5.3.2 Other physical and biological
constraints........................85
2.6 Rainbow trout...........................................87
2.6.1 Adult phase of life cycle....................87
2.6.1.1 Sport fishery harvest........•••...87
2.6.1.2 Adult population indices...........89
2.7 Burbot...92-
2.6.2
2.6.1.3 Habitat and environmental parameters
associated with the adult phase of
the live cycle..........•.••.....•.89
Reproductive phase of life cycle
and juvenile distribution and abundance......91
2.7.1 Adult phase of life cycle.........••.........92
2.7.1.1 Sport fishery harvest..............92
2.7.1.2 Adult population indices...........92
2.7.1.3 Habitat and environmental
parameters associated with
the adult phase of the life
cycl e............. . . . . . ...... . . . . . . .93
2.7.2 Reproductive phase of life cycle and juvenile
distribution..................................94
-
-
2.8 The Whitefish -Round and Humpback complex
and the anadromous Bering cisco........................95
2.8.1 Adult phase of life cycle....................95
2.8.1.1 Sportfishing and other harvests....95
2.8.1.2 Adult population indices...........95
2.8.1.2.1 Round whitefish..........95
xvii
2.8.1.2.2 Humpback whitefish
complex..................96
2.8.1.2.3 Bering cisco.............96
2.8.1.3 Habitat and environmental parameters
associated with the adult phase of
life cycle..........•..97
2.8.2
2.8.3
Reproductive phase of the life cycle.........98
Juvenile rearing and migration...............99
2.9 Eulachon 100
2.9.1
2.9.2
Freshwater reproduction phase of
life cycle..100
2.9.1.1 Sport fisheries harvest 100
2.9.1.2 Adult escapement 10]
2.9.1.3 Habitat and environmental parameters
associated with spawning ..•........101
Juvenile emergence,rearing,and
mi gration.. .... . .... . . ............. . . . . . . . . . . .102
2.10 Miscellaneous game species (Arctic grayling and
Dolly Varden)..........••.."'103
2.10.1
2.10.2
2.10.3
Adult phase of the life cycle •.....•.........103
2.10.1.1 Sport fishery harvest.....103
2.10.1.2 Adult population indices 104
2.10.1.3 Habitat and environmental parameters
associated with the adult phase of
the life cycle .....•.•.............104
Reproductive phase of the life cycle •........105
Juvenile rearing and migration 105
..'
2.11 Other species of the Susitna River drainage 107
2.11.1
2.11.2
2.11.3
Threespine stickleback ...............•.......107
Longnose sucker ..•...........................108
Arctic lamprey...............................109
xviii
TABLE OF CONTENTS (Continued)_.
2.11.4
2.11.5
S1i my scu1pin.•••. •. •. . . •••. •. . •. .. . . . . . . . . . .11 0
Other specles.........•..••......111
3.THE FISHERIES STUDIES WITHIN THE BOUNDARIES OF THE
PROPOSED IMPOUNDMENTS ABOVE DEVIL CANyON .....•.........•.•..112
3.1 The fishery resources of the clear water tributaries
of the impoundment zones .....••....•...................112_.
-
3.1.1
3.1.2
3.1.3
Population estimates or indices of species
present within the clear water tributaries...113
Population dynamics and harvest effects on
grayling in the tributaries .........•...••...113
Relationships of growth,population,and
production data to general and site specific
habitat variables ••.•.•..•.••................115
-
3.2 The fisheries resources of the mainstem Susitna
within the impoundment zones ......•....•.......•.......116
3.3 The fisheries resources of the lakes within the
impoundment zone.......................................117
4.SUMMARY OF THE INSTREAM FLOW RELATIONSHIPS OF THE
FISHERIES RESOURCES DOWNSTREAM OF DEVIL CANyON 118
4.1 Introduction ••...•...•....•........•••.........•.......118
4.2 Key findings of fisheries studies downstream of
Devil Canyon to the Chulitna confluence •.•.•...........118-4.2.1
4.2.2
Principal instream habitat types 118
Primary species composition and
seasonal availability of instream
habitat types................................119
4.2.2.1 Mainstem and side channel
4.2.2.2
4.2.2.3
4.2.2.4
habitats .•....•••..................119
Si de slough habitats...............120
Upland slough habitats.............121
Tributary and tributary
mouth habitats •....•...............122
4.2.3 Influence of mainstem discharge and
water quality on instream habitat
types........................................123
xix
TABLE OF CONTENTS (Continued)
4.2.3.1
4.2.3.2
4.2.3.3
4.2.3.4
Mainstem and side channel
habi tats.. . . . . . . . . . . . . . . .. . .... . . . .123
Side slough habitats 125
Upland slough habitats.............127
Tributary mouth habitats...........128
4.3 Key findings of fisheries studies downstream
of the Chulitna confluence 129
4.3.1 Principal instream habitat types 129
4.3.1.1
4.3.1.2
4.3.1.3
4.3.1.4
4.3.1.5
Mainstem/side channel 129
Side slough 130
Upland slough 130
Tributary......131
Tributary mouth 131
4.3.2 Primary species composition and seasonal
ava i1abi 1i ty of i nstream habi tat types.......132
4.3.2.1 Mainstem/side channel habitats 132
4.3.2.2 Side slough habitats 133
4.3.2.3 Upland slough habitats..............133
4.3.2.4 Tributary and tributary mouth
habitats...........................134
4.3.3 Influence of mainstem discharge and
water quality on instream habitat types ....•.134
4.3.3.1 Mainstem/side channel habitats 134
4.3.3.2 Side slough habitats 135
4.3.3.3 Upland slough habitats..............135
4.3.3.4 Tributary mouth habitats.....135
4.4 Limitations of the available data base 136
4.4.1
4.4.2
Habitats in the reach downstream
of Devil Canyon to the Chulitna
confluence...................................136
Habitats in the reach downstream
of the Chul itna confluence...................138
5.CONTRIBUTORS ...........................•....................140
6.ACKNOWLEDGE~1ENTS... . ......... . . . . . .... . . . . . . . . . .. . .... . . . . . .142
7.LITERATURE CITED............................................143
8.BIBLIOGRAPHY.......••...•.........149
9.GLOSSARY OF COMMON AND SCIENTIFIC NAMES 152
xx
TABLE OF CONTENTS (Continued)
10.APPENDICES a
-
_.
-
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
Appendix I
Appendix J
Appendix K
Analysis of the species selectivity of
fishwheels for the capture of adult salmon
in the Susitna River
Timing and passage of adult salmon in
the mainstem Susitna River and access
into selected sloughs upstream of the
Chulitna River confluence
Observations of salmon spawning
habitat in selected sloughs of the
Susitna River
Modeling of hydraulic conditions
and chum salmon spawning habitat
in selected Susitna River sloughs
Effects of mainstem Susitna discharge on
total wetted and backwater surface area at
selected study sites
Influence of habitat parameters on
distribution and relative abundance
of juvenile salmon and resident species
Use of major habitat types by juvenile
salmon and resident species
Habitat relationships of juvenile salmon
outmigration
A model of the effect of incremental
increase in sport fishing on population
structure of Arctic grayling above
Devil Canyon
Age-length curves and growth of Arctic
grayling and rainbow trout
Evaluation of Arctic grayling spawning
and rearing habitat and notes on salmon
spawning in the impoundment study area
-
a Appendices included under separate binder.
xxi
LIST OF FJGURES PAGE
Figure 2-1
Fi gure 2-2
Figure 2-3
Figure 2-4
Figure 2-5
Figure 2-6
Figure 2-7
Figure 2-8
Figure 2-9
Figure 2-10
Fi gure 2-11
Figure 2-12
Seasonal use of macro-habitat by chinook
salmon above the Chulitna River confluence
(RM 98.5). . . . . . . . . . . . . . . . . . . . . . . . . . . •. . . . . . . . . . . 5
Harvest summary of Cook Inlet and Susitna
River chinook salmon stocks.....................7
Summary of the population estimate and sport-
fish harvest for adult chinook salmon within
the Susitna River...............................9
The seasonal variation in distribution and
relative abundance of chinook salmon
juveniles at DFH sites on the Susitna
River,June through September,1982.............17
Seasonal use of macro-habitat by coho
salmon above the Chulitna River
confluence (RM 98.5)..29
Harvest summary of Cook Inlet and Susitna
River coho salmon stocks........................30
Summary of the population estimate and
sportfish harvest for adult coho salmon
within the Susitna River........................32
The seasonal variation in distribution
and relative abundance of coho salmon
juveniles at DFH sites on the Susitna
River,June through September,1982.............37
Seasona 1 use of macro-habitat by sockeye
salmon above the Chulitna River confluence
(RM 98.5)...............•.............•.........45
Harvest summary of Cook Inlet and Susitna
River sockeye salmon stocks.....................46
Summary of the population estimate and
sportfish harvest for adult sockeye salmon
within the Susitna River........................48
Seasonal variation in distribution
and relative abundance of sockeye
salmon juveniles at DFH sites on the
Susitna River,June through September,
1982 .........•..................................54
xxii
_.LIST OF FIGURES (Continued)
_.
Figure 2-13
Figure 2-14
Figure 2-15
Figure 2-16
Figure 2-17
Figure 2-18
Figure 2-19
-----_._-_.__•••<_•••
Seasonal use of macro-habitat by chum
salmon above the Chulitna River confluence
(RM 98.5)•...............•...•..................
Harvest summary of Cook Inlet and
Susitna River chum salmon stocks ..•.•...........
Summary of the population estimate and
sportfish harvest for adult chum salmon
within the Susitna River .
Seasonal variation in distribution
and relative abundance of chum salmon
juveniles at DFH sites on the Susitna
River,June through September,1982 ....•........
Seasonal use of macro-habitat by pink
salmon above the Chulitna River confluence
(RM 98.5)•......................................
Harvest summary of Cook Inlet and
Susitna River pink salmon stocks •.......•..•..•.
Summary of the population estimate and
sportfish harvest for adult pink salmon
within the Susitna River ....••..•...............
xxiii
6",
.L
63
65
72
78
79
81
LIST OF TABLES
Table 2-1
Table 3-1
Summary of resident sport fish harvest in the
Susitna River.1977-1982 .......•..•............
Arctic grayling population estimates by
tributary habitat evaluation location.
Proposed Impoundment Area.1982 •..............
xxiv
PAGE
87
]14
1.INTRODUCTION
1.1 Purpose of report
This report is designed to integrate,on a species level,dat~collected
hy the Alaska Department of Fish and Game (ADF&G)Su Hydro Aquatic
studies during 1981 and 1982.The material is reported separately for
study areas above and below Devil Canyon because of the different tyres
of impacts anticipated.
The report provides a synopsis of the findings on each of the target
species of both resident and anadromous fish,and an analysis of fish
and habitat data contained in the ADF&G 1982 Phase II Basic Data reports
(1983a,b,c,d).With the exception of summary tables or figures,data
and analysis presented in the Basic Data reports are not repeated.The
reader of this report should refer to those volumes when supporting or
more specific data are desired.Extensive literature reviews for the
species of fish discussed have not been included.Literature reviews of
the freshwater habitat relationships for some of the species have been
compiled hy the U.S.Fish and Wildlife Service and are available for a
broader perspective on the Susitna River fish species (see
Bibliography).Life histories for all species mentioned have been
summarized by Hart (1973),Morrow (1980),and Scott and Cy'ossman (1973).
A glossary of common and scientific names is enclosed at the end of the
report.
1
,.,---,--,_._--_.---,---------------
1.2 Study objectives
Detailed study objectives are reported in earlier ADF&G reports (1979,
1981a,b,c,d,e)and a synopsis of the major objectives is repeated
below:
a.Determine the seasonal distr-ibution and relative abundance of
adult anadromous fish populations within the study area.
b.Determine the seasonal distribution and relative abundance of
selected resident and juvenile anarJromous fish populations
within the study area.
c.Cha racteri ze the seasonal habitat requi rements of selected
anadromous and resident fish species within the study area and
the influence of mainstem discharge on the availability of
these habitats.
Spec ifi c ana 1yt i ca 1 components a re presented in the append ix of th is
report to complement the major findings discussed in this report.
1.3 Utility of the report in impact analysis and mitigation
planning
The mitigation of adverse impacts of the project by appropriate flow
management can be analyzed by use of the same types of data that are
used to determine potential impacts of the project.The response of the
2
.'
fish populations to a particular flow regime can be estimated by
determining the response of their habitat to natural variations in
discharge under pre-project conditions.Adverse flow related impacts of
the project have the potential to be avoided or minimized by developing
downstream flow release schedules that provide hydraulic and \"at{~r
quality conditions suitable for the fish species present.
This report and associated data analysis provides information to assist
with:
1.Preparation of the impact statement necessary for application
of the Federal Energy Regulatory Commission (FERC)license.
-2.Description of the existing environment and the magnitude of
the resource that will potentially be impacted.
3.Determination of the effects of natural flow alteraUons on
adult anadromous species,important resident fish species,
rearing anadromous fish species,and the habitat necessary to
sustain populations of those species.
This report is also useful in evaluating other potential effects of the
project such as thermal alteration,geomorphological changes,icing
conditions,and alterations of water quality.
3
-----------
c.RESULTS AND DISCUSSION OF THE FISH AND HABITAT STUDIES ON THE,
SUSITNA RIVER BELOW DEVIL CANYON
The current state of knowl edge concerni ng the 1 i fe hi story of each of
the major species of resident and anadromous fish that have been found
in the Susitna River below Devil Canyon is discussed in the following
sections.
2.1 Chinook salmon
Chinook salmon,more commonly cal1ed king salmon in Alaska,are an
important sport fishing species in the Cook Inlet area with use by
subsistence fisheries and "incidental harvest by the commercial
fisheries.Figure 2-1 depicts the periodicity of the various life
stages of chinook salmon in macro-habitat areas that have been
identified in the Susitna River above the Chulitna River conf1uence.
This section of the report discusses the fresh water phases of the
chinook salmon 1 ife cycle that occur in the portion of the Susitna basin
that may be affected by the proposed Susitna Hydroelectric project.
2.1.1 Adult phase of life cycle
The Susitna River escapement of chinook salmon peaks in late June and
is essentially completed by mid July (ADF&G 1983a).During this
migration,very little commercial harvest occurs.This species is a
major sport fish in the Cook Inlet area and is sought after extensively
4
1S·M•••SpeculotlonbOledonInferenceefro,"e.lttinOdatoM.Moinate",aSldechon".I.S"SideSioughaSUaU9londSIOUGhaT".Tributor",andTributoryMouth•T'"SuS·MT'".:..~~:r~~~~1~11a';::~';ic....,c,.s.Su~·..II•!i..15!::~i~:-~.tMT'"SuS·M~..'"~·..III~·..II~~~~~~~I~~'?a..;Q.~il.ei.ik';&....,~..,"'~.J..,c..,~NoUs.CHINOOKITolollyOtpenel..,•()c:0Hea,y-UnL-0a.e-•>Moel.al.-UI.0(Jl'iiIX:-0Ror.orJCLittIIlJItII)'Qc:AdultMigrotionSpawningaIncubationRearingJuveniles0+Reari~Juveniles1+Figure2-1.Secsonaluseofmacro-habitatbychinooksalmonabovetheChulitnaRiverconfluence(RM98.5).DatasummaryfromADF&G(1983a,1983b).
in portions of the Susitna River basin and elsewhere in the Cook Inlet
area.There is also a small subsistence fishery at Tyonek.Histori-
cally,chinook were an important commercial species;during the 1950's,
large numbers were harvested.
2.1.1.1 Adult harvest by sport,commercial,and subsistence
fi sheri es
The harvest estimate is illustrated in Figure 2-2.Although none of the
clear water tributaries above the Chulitna River confluence are
currently open to sport fishing for chinook greater than 20 inches in
length,some fish migrating to spawning grounds in these tributaries are
probably harvested when they hold at the mouth of lower river
tributaries such as the Deshka River,Willow Creek,Sheep Creek,dnd
Montana Creek.This holding behavior was commonly observed by the radio
telemetry studies in both the 1981 and 1982,(ADF&G 1981a,1983a).
A commercial harvest of Cook Inlet chinook occurs incidentally to the
sockeye salmon harvest.Most of these chinook salmon are harvested fron!
the stocks destined for the Kasilof and Kenai Rivers.Susitna River
chinook do not contribute significantly to this fishery.The village of
Tyonek,on the west side of Cook Inlet,is currently authorized a
harvest of chinook salmon for subsistence purposes.Up to 4,200 fish
are allotted annually for this purpose and a harvest of 1,500 fish was
recorded in 1981.The take of chinook salmon in sport fisheries in the
Susitna River was estimated to be 7,250 fish in 1981 (Mills 1982).This
estimate includes lIimmature ll fish (less than 20 inches in length).
6
I/'."r···-···-//...,---.....;;....."/'.....,,"""/I.",I....,..t~----UPPERCOOKINLETHARVEST(INCLUDESNON·SUSITN...STOCKS)- - -SUBSISTENCE-TYONEKEASTSIDESPORTFISH.-------WESTSUSITNASPORTFISH._•••_•••-TOTALSPORTFISH.53025101520'-JotfJI i [litiiiIiiIiif ,Iii1960616263646566676869707172 73747576 77787980811982.-TOTALCHINOOKALLSIZECLASSESYEARFiqure2-2.HarvestSl;mrnaryofCockInletaroSusitnaRiverchinooksc"imonstocks.HarvestdatafromADF&G(198lf)andk.Florey(Personalcommunication,ADF&G,Anchorage),subsistencecatchdatafromFoster(1982)andsportfishcatchdatafromMills(1982).Datafrom1982arepre1im;nary .
2.1.1.2 Adult escapement
A complete estimate of escapement of adult chinook salmon into the
Susitna y'iver drainage is not available.The annual sport fish aer'ial
survey counts in clear water tributaries have provided escapement
i ndi ces (Fi gure 2-3).'These surveys were conducted duri ng the peak of
chinook salmon spawning from 1977 to 1982.Aerial survey chinook counts
in the last years of these surveys have been very low due to limited
visibility caused by high water conditions present during the peak
spawning period.
Aerial survey data can be compared with the escapement estimates that
were made using Petersen estimates at the ADF&G Sunshine,Talkeetna,and
Curry field stations during the 1982 season (Figure 2-3).The numbers
of chinook salmon indicate the number of fish passing the fishwheel
tagging stations but not necessarily the total number of chinook that
spawn above these sites because significant numbers of tagged chinook
were observed in lower river tributaries downstream of the tagging
operation.
Differences between the aerial survey population estimates and the
Petersen estimates can be explained by two sources of error.First,the
aerial counts miss some of the fish that have not yet entered the clear
water drainage or have spawned and died,thus providing an underestimate
of the total numbers of spawners.Second,mark-recapture estimates are
probably overestimates because some of the fish initially migrating past
these sites later spawn below the Sunshine,Curry or Talkeetrw
8
r 40U)
lL.
lL
0
U)
<:)
z,...<l:
U)30~
0r
~-
20-
-
-
-
-
,...
-
-
-
80
70
60
50
10
CH I NOOK
E,tlmated Total Sportfl,h
Hornlt of the SUIltna River
Toto I S ulltna Aeria I Escapemenl
Index
Eleapement 'nd eJ.of Tributor ies
of Portage Creek and 1nd I an R jve r
Peterson Population Esl ima'es
at Talkeetna Station
Peterlon Populntion Estimates
at Sunshine Station
YEARS
X No dolo collec.ed because of hillh water
••Indel(tolola incomplete becauae ot POOl"
somp1inll conditions
Blank columns indicate no dolo collec!ed
-
-
Fiqure 2-3.Summary of the population estimate and sportfish
harvest for adult chinook salmon within the Susitna
River.Sportfish harvest data fl~orJl Mills (19S;n ('fld
escapement and population estimates from ADF&G (1983a).
9
fishwheel sites.Some of the biases of the fishwheel capture and sonar
apportionment methods used and suggestions of the possible reasons for
differences in est imates made by the two methods are di scussed in
Appendix A and in ADF&G (1983a).
2.1.1.3 Habitat and environmental parameters associated with
the adult phase of the life cycle (up~;tream
migration,passage and spawniny)
During the upstream miyration adult chinook encounter environmenta-j
conditions that may reduce spawning success.The most obyious
influences are the discharge and temperature of the mainstem Susitna and
of the natal tributaries.By monitoring the behavior of chinook during
natural variations in discharge and temperature,and by examining the
hydraulic conditions at the mouths of the clear water tributaries,
insight can be obtained into the effects of flow alteration on the
Susitna chinook salmon.
2_1.1.3.1 Discharge,water quality,and temperature
relationships with the adult chinook salmon
migration
The U.S.Geological Survey (USGS)monitors the discharge of the mainstem
Susitna above and below the Chulitna River confluence.The gages are
located at the Gold Creek Bridge and at the Parks Highway bridge near
Sunshine Creek (called the Sunshine station).These flow data are used
as the primary basis to compare responses of the fish and other
10
-
physical habitat parameters to changes in mainstem flow.Temperature
data are also collected at several mainstem locations.The effects of
mainstem temperature on adult salmon behavior is examined in Appendix B.
There are two sources of biological information that are used to
correlate the effects of these environmental variables on fish migratory
behavior.The movement of the fish upstream has been monitored by use
of fishwheels,sonar and ground surveys,and the movement of individuals
has been monitored by radio telemetry.Within the natural variations in
temperature,no effect of temperature on fish migration was observed
during the 1982 migration.The influence of discharge on the behavior
of the fish was detectable at the higher discharge levels.At higher
discharge levels,an inverse correlation exists.Upstream movement of
adult chinook was slowed when peak flows occurred during the migration.
Although chinook salmon movement also correlates with a decr'ease in
temperature,the discharge variation was greater and is believed to he
the dominant factor causing the decreased rate of movement.This
behavior was also observed during the 1981 chinook migration.Similar
effects have been observed with the other species of salmon.Variation
in discharge in the lower flow regimes were not observed to influence
the behavior of adult chinook salmon.
Passage of chinook salmon through lower Devil Canyon was documented for
the first time by the Alaska Department of Fish and Game during 1982.
Chinook salmon were observed spawning at the confluence of two small
clear water tributaries within the Devil Canyon impoundment zone and
11
spawning chinooks were also observed in the same two tributaries.These
sites were not examined prior to 1982 during the peak of the chinook
migration.The relatively low flows that occurTed during the chinook
run of 1982 may have allowed these fish to move into these areas.
Hydraulic conditions supporting passage of fish into the mouths of the
clear water tributaries,Indian River and Portage Creek,has been
examined in detail (Trihey 1983).The influence of mainstern flow on the
passage of chinook salmon into these tributaries was analyzed by
examination of the stream mouth gradient and associated water velocities
and the distance that such velocities are likely to occur under
alternative flows of the mainstem Susitna.This analysis concludes that
passage into these two tributaries is not likely to be affected by lower
flows.
When encountering high concentrations of supersaturated dissolved gas at
the base of hydroelectric projects,adult salmon are known to suffer
from gas bubble disease (Weitkamp and Katz 1982).Measurements of total
dissolved gas concentration below the Devil Canyon rapids gave readings
up to 116%of saturation.Level s of over 120%of saturation are
predicted for discharges over 50,000 cubic feet per second (cfs)at Gold
Creek (ADF&G 1983c).The relatively low flow period of August and
September-,1982,produced levels of 113 percent total dissolved gas,
when the gas levels were being continuously monitored.These levels
could create serious problems for juvenile fish in hatcheries if they
could not escape the gas concentrations by sounding to deeper areas.
The levels are below the threshold that would be expected to adversely
12
affect adult or juvenile chinook salmon below the rapids where
sufficient depth is available (Weitkamp and Katz,1982).The relatively
low rates of dissipation of the naturally entrained dissolved gas in the
reach of river below the rapids suggests that higher levels rf
supersaturation that may be created by water spillage at either of the
proposed dams would not dissipate sufficiently to reduce the hazard to
either adult or juvenile chinook salmon as well as other species of
salmon.
Habitat requirements for chinook salmon spawning in the Susitna River
have not been established because this species spawns primarily in the
tributaries.However,such information would be useful in assessing if
adverse effects of the project can be mitigated through flow regulation
to support spawning populations in the mainstem under post-project
conditions.The lack of a data base on this aspect of the life history
of Susitna chinook stocks forces the analysis to be limited to
literature values for the species at this time.
One limiting factor to chinook salmon spawning in the mainstem Susitnd
and side channels is probably the amount of suitable substrate
available.High velocities during the spawning period and the
associ ated probabil ity of redd scouri ng may 1 imit spawn i ng habita t.
Because of the early timing of the chinook runs,the August floods that
commonly occur in the system could destroy mainstem redds.The
substrate is very unstable during these periods,with major shifts and
movements of spawnab 1e gravel s occurri ng frequently.Because of the
high velocities in the mainstem,much of the channel of the reach
13
of river above the Chulitna confluence is armored cobble,unsuitable for
spawning.The stability of the substrate and velocities that occur in
selected side channel areas of the mainstem under various discharges has
not yet been quantified.Themal,substrate,velocity,and depth data
collected at areas currently used by spawning chinook salmon in Portage
Creek and Indian River could be used to provide an estimate of the
post-project potential for these side channels areas to support chinook
salmon redds.
2.1.1.3.2 Other factors that influence the spawning success of
chinook salmon
The limitations to spawning by chinook salmon in the Susitna River are
largely unknown.The influence of turbidity on the selection of redds,
insufficient dissolved oxygen for incubating eggs resulting from
the settling of suspended sediment,and the cover or depth requirements
to provide cover from predators,may all limit the ability of the
mainstem Susitna to support chinook salmon spawning.
Ice processes may be a major factor.During the ice formation process,
channels can become dewatered,and bed scouring may occur in isolated
areas.Intragravel temperatures may vary greatly in a short period of
time,and may adversely effect embryo or alevin survival.An
understanding of the effects that ice processes have on flow patterns in
potential spawning sites and the effects on winter thermal
characteristics are essential to define limits to spawning under current
flow conditions or under regulated conditions.
14
2.1.2 Juvenile rearing and migration phases
Unlike the spawning,incubation,and emergence phases of the life cycle,
the chinook rearing phase occurs in habitats that are directly affected
by mainstem Susitna discharge,turbidity,and temperature.
The focus of the 1981 and 1982 Juvenile Anadromous Studies was on
determining the relative abundance of each species and the genera 1
habitat types associated with their rearing.The general distribution
data has been used to select specific sites for more detailed
investigations regarding the suitability of selected habitat areas for
juvenile chinook salmon,and for measuring the response of these habitat
areas to changes in mainstem discharge.This has provided the first
step in assessing the response of juvenile salmon to incremental
alterations in flow.
2.1.2.1 Relative abundance of juvenile chinook salmon
Lluvenile chinook salmon emerge from the gravel of their natal clea,'
water tributaries in March or April.From this time until they
outmigrate into Cook Inlet,usually the following summer,they an:
actively feeding and are dependent upon suitable habitat for rear'ing.
Young of the year chinook (Age 0+)apparently spend the first two
months in the vi ci nity of thei r nata 1 areas after emergence (Morrow
1980).They begin redistributing downstream shortly afterward and have
been collected in small numbers at habitat sites associated with the
15
mainstem Susitna (Figure 2-4).Some rearing by young of the year
chinook salmon also occurs within clear water tributaries where
significant numbers of fish are present until fall.After the second
week in August,most of the population apparently outmigrates into the
mainstem Susitna to overwinter.Most of the juveniles that compose the
populations of chinook salmon from Portage Creek and Indian River~are
dependent upon habitat condition')in the mainstem Susitna during this
period (late August to May of the next year).
An outmigrant trap was operated from June 18 to October 12,1982 at
river mile 103.0.Age 0+chinook were collected throughout the su~ner
with peaks in July and September.This probably reflects a general
redistribution into rearing sloughs and tributary mouths or small
backwater areas throughout the system.The Age 1+fish made up 40
percent of the fish collected during the period that the trap was in
place.Because it is suspected that larger numbers outmigrated before
the smo1t trap became operational~those juvenile chinook salmon which
\<Jere spawned in the reach of the Susitna River above the Chu1 itna
confluence may use this reach for most of thE'ir fresh water rearing
cycle.
The trapping efforts that occurred at sloughs and tributaries above the
Chulitna River during the 1981 and 1982 open water seasons indicated a
substantial difference in catch rates between the years,when the same
locations were compared.Three hypotheses that could account for these
differences are:
16
SEPT.
I 11
00,,0
00
00
00
00
00
00
00
00
00
CANYON
JULY AUG.
I n I ][
00 0-o 0 ~.,
00 0 ~
00 00
00 0 ~
00 00o00.,
00 00o00"
00 00
00 00
Relative Abundance Key
o Absent aoTrace1to 10
ij Present 11 to 71
•Abundant 72 +over
-.:flo samp 1e
15--"ij 0 0 0 0
18--0 0 0 0 COO
~-------17-0 0 .""0 0 0
_-------13-C"0"0 0 0 0
~-------14-""0",,0 0 0
JUNE
I ][
1-0
2-0 0
3-0 0
4-0 0
5-0 0
a-O 0
7-0 "8-0 0
9-0 0
~--------iO-0 0
1+-,,...----------11-0 0
ri!----------12-0 ~0 0 0 0 ,,0
·1.Portage Creek
2.Slough 21
3.Slough 20
4.Slough 19
5.Indian River
6.Slough 11
7.Fourth of July Creek
8.Slough 9
9.Slough BA
10.·Lane Creek
11.Slough 6A
12.Whiskers Creek
13.B1 rch Creek
14.Sunshine Creek
15.Rabideux Slough
16.Whitefish Slough
17.Goose Creek
Figure 2-4.The seasonal variation in distribution and relative
abundance of chinook salmon juveniles at DFH sites or:
the Susitna River,June through September,1982.Taken
from ADF&G (1983b).
17
(1)The 1981 spawning was less successful than 1980 spawning
and/or the incubation portion of the 1981 brood year 1He
cycle had a lower survival than the 1980 brood year which
caused a decrease in number of fi sh at the sites exami ned
above the Chulitna River.
The only data that directly support this hypothesis are the low numbers
or non-existent catches dut'ing the 1imited sampl ing effort that was
undertaken in Portage Creek and Indian River.Numbers collected during
the 198]open water season were also quite low although large increases
in the catch from these tributaries occurred during the 1981 fall
outmigration.
(2)The low flow conditions of the mainstem Susitna River during
the 1982 open water season reduced the capability of juveniles
to pass into the sloughs and tributary mouth areas,and
therefore decreased the utilization of these habitat types in
the upper river.
This hypothesis is inferred from the examination of distributional data
between 1981 and 1982.At sloughs and other sites sampled both years,
the catch per unit effort was substantially lower.The catch of
outmigrants of Age 0+and 1+at the outmigrant trap suggests that
movement of chinook occurs in the mainstem during the course of the
summer and may reflect a continual downstream displacement into suitable
rearing habitat.Since data were not collected on outmigration rates
during the 1981 open water season,we have no comparable data to
18
determine what factors may have affected the catch rates at the
outmigrant trap.
(3)The decreased catch rates at the designated habitat sites may
refl ect a loss of usable habi tat at these sites because of
decreased stage related to lower mainstem Susitna flows.
Qualitative data on the availability of cover at the sloughs and tribu-
tary mouths influenced by mainstem back up suggests cover may decrease
substantially with decreasing mainstem discharge.Areas of brush,
undercut banks,logs,and other types of overhead cover were often
dewatered under the 1982 low flow conditions.These conditions may have
contributed to the lower numbers of juveniles at these sites because of
a behavioral response to the lack of cover.
The change in abundance of juvenile chinook salmon observed in the major
habitat types may be explained by any or a combination of the above
three hypotheses.The 1983 open water study design should provide
information that will help establish the importance of these factors ir
influencing the relative abundance of chinook juveniles in the system.
Vuriations in the distribution of chinook fry within the specific
habitat sites and possible causes are addressed in the following
section.
19
2.1.2.2 Habitat and environmental factors associated
with the juvenile phase of thp.life cycle
The habitat utilized by juvenile chinook was investigated during ]981
and 1982.During the 1981 field season,habitat data collection
demonstrated the range of conditions that were associ ated with mi nnow
trap catches of juvenile chinook.This habitat data was collected to
obtain distributional information over the general habitat types that
occur in the system (ADF&G 1982).
The 1982 sampling program was designed to provide additional dis-
tributional data on chinook salmon juveniles and to specifically test
factors that may affect their distribution.During the 1981
investigations,it had been noted that the slough habitats and tributary
mouths consistently provide a higher catch per unit of effort (CPUE)
than other habitats.It was also observed that the CPUE varied
considerably with the time of year and the location.It was
hypothesized that these influences reflected the migratory behavior of
this species so that the CPUE data often reflected these conditions
rather than micro-habitat conditions.
Influences of the mainstem discharge caused two major effects on many of
these habitat sites.The high water flows that overtopped the head of
many of the sloughs during the open water season created sudden and
substantial increases in discharge within these areas and altered
habitat significantly.The mainstem also created a backwater effect,
dependent on stage of the mainstem,that extended up into the sloughs
20
and tributary mouths.This area extended for over a mile in some of the
low gradient sites,or less than 50 feet where the mouth of the
tributary or slough had a relatively steep gradient.The surface.areas
of the backwater regions are dependent upon tributary flow,flow
overtopping the head of some of the sites,and the extent of backup at
the mouth.The juvenile study program was designed to determine the
response of the surface area of these backwater IIzones"to changes in
mainstem discharge and to test if the CPUE was different between these
zones and other adjacent sites at any given point in time.By combining
these two components,an estimate of the influence of mainstem discharge.
on juvenile salmon habitat can be made.The analysis of this data is
presented 'in Appendix F and is used as the basis·for the following
discussion.
2.1.2.2.1 Physical habitat conditions of rearing
juveniles
Discharge (velocity and depth)relationships and their effects on
indices of available habitat
Investigations examining the effects of discharge on rearing habitat of
juvenile fish frequently have employed hydraulic models to simulate
reaches of streams under variable discharges.The resultant model
predictions of depth and velocity have been compared with the velocities
and depths associated with the natural distribution of fish.Ey
incorporating the natural selectivity of fish for particular depths and
21
velocities into a habitat simulation model,the available habitat ~t any
particular discharge has been estimated (Bovee 1982).
The ADF&G Susitna studies employed a similar concept but used a more
general approach to addressing the response of juvenile chinook to
mainstem discharge changes.Sevt~nteen designated habitat locations at
the mouths of tributaries and sloughs,which had relatively high CPUE
rates during the 1981 investigations,were selected.There were twelve
sites above the Chulitna River confluence and five below.All of these
sites were selected primarily because of importance to juvenile fish
during the previous season,the logistical convenience of sampling,and
because they provided a good representation of the various habitat types
present.The response of the phys i ca 1 habi tat component was based on
the Gold Creek gaging station of the USGS for the upper reach of river
and the Sunshine station for the lower.
The effects of mainstem discharge on chinook salmon juvenile rearing
habitat at representative sites are presented in Appendix F (Appendix
Figures F-3 to F-6).The habitat response to discharge is limited to
the study area defined in the appendix at each of the designated habitat
locations.Because these locations were selected due to their
comparative importance to rearing juveniles,responses to mainstem
discharge of the habitat at these sites probably reflects habitat
conditions for many of the fish within the reach of river examined.
22
There was little difference in distribution of chinook salmon in
backwater zones and the areas not backed up by the mainstem.Therefore,
the projected changes in habitat,as reflected by these lones,
paralleled the surface area of all zones.This information reflects
only the minimum decreases or increases in habitat with changes ';r
mainstem Susitna discharge.
Water quality and thermal relationships
The water quality parameters investigated with respect to juvenile
chinook distribution included dissolved oxygen,conductivity,pH,
and turbidity.During the open water season,temperature and turbidity
are probably the main factors that influence the distribution of juve-
nile chinook.
Temperature affects the basic metabolism of fish and the warmer areas of
a cold water river system such as the Susitna often attract juvenile
fish (Appendix F).Where there were significant thermal differences at
the mouth of clear water tributaries,juveniles were frequently found in
the warmer water.This may also explain why some sloughs thc1t have
warmer temperatures during the winter also have higher densities of
juvenile chinook during the winter.
Turbidity affects the distribution of juvenile salmon in several ways.
It provides cover from predation but also limits primary production,
food availability,and probably feeding efficiency.However,the 1982
23
-----------_....-'"'-'~
studies did not demonstrate any effects of turbidity on chinook
distribution (Appendices F and G).
2.1.2.2.2 Timing of outmigration from the tributaries,
sloughs and mainstem and its relationship
to environmental changes.
The timing of outmigration and the factors that influence outmigration
of fish in the Susitna system have been investigated.The following
factors probably play some role in determining outmigrant timing.
(1)Photoperiod.The response to the length of day is probably an
inherited behavioral stimulus for outmigration.The out-
migration timing probably corresponds with optimal survival
conditions in the estuary or ocean environment and may
correspond to plankton blooms.
(2)Size of juvenile.There are some data available that indicate
that juveniles salmon that grow faster may outmigrate earl iey'.
Studies on the Deshka (Delaney et al.1981),indicate that
during even year pink salmon runs when juvenile chinook feed
heavily on pink salmon eggs the young of the year juvenile
chinook outmigrated into the mainstem Susitna and do not
overwinter in the Deshka River system.Juveniles in other'
tributaries have been observed to remain until the next
spring.These fish are generally smaller than the earlier
outmigrants.
24
(3)Physical habitat conditions.Water temperature can influence
the rate of development,and therefore alter the olJtmigration
timing of juvenile chinook.Other factors that will affect
their available food supply,such as changes in turbidity and
flow stability,will also affect their growth rate and ITIay
cause alterations in the outmigration timing as discussed in
(2)above.Other effects that are more likely to be observed
include the response of juveniles to the discharge
fluctuations of the mainstem Susitna.The rates of
outmigration of juvenile chinook have been positively
corre 1ated with the daily rna i nstem di scharge measurements at
Gold Creek (Appendix H).
Reasons for this correlation include the influence on access in and out
of slough rearing habitats by the stage of the mainstem.Increased
depths and velocities during outmigration probably provide a behavioral
stimulus to move out into the mainstem.
In summary,observed timing of outmigration can be influenced by several
factors,but has probably evolved to maximize survival of the juveniles.
Mainstem discharge probably influences the short term movements of fish
into the system but the size of the individual and behavioral response
to photoperiods may be the dominant factors controlling outmigration.
25
2.1.2.2.3 Food supply for rearing juveniles and its
relationship to other parameters and
preference dependency of species in the
system.
The 1982 studies initiated an investigation of the selectivity of
chinook juveniles for aquatic invertebrates at slough and tributary
mouth sites.Comparisons were also made between the invertebrate
community composition of the different types of sites.These studies
were designed to provide some initial insight as to whether or not the
use of different types of habitat associated with the Susitna River can
be explained in terms of food type availability and selectivity.
The speci es compos iti on of the invertebrate community was di ss imil ar at
all sites examined with chironomid larvae the dominant form present.
The larvae of the chironomid was also consumed in greater numbers and
frequency by juvenile chinook and thus appeared to be a preferred food
item.However,food item selectivity data did not suggest that
invertebrate community composition had a major influence on the
distribution of juvenile chinook which points to invertebrate density as
a major factor.However,no attempt was made to quantify the
invertebrate communities present.The relationship between invertebrate
densities and the density or growth rates of juvenile chinook awaits
further study.
Terrestrial insects also comprise a significant portion of the juvenile
chinook diet,suggesting the presence of overhanging vegetation or
comparatively large amounts of stream bank per unit of wetted surface
26
area,may provide important sources of food for rearing juveniles.This
hypothesis is supported by the observation that juvenile chinook rearing
at Fourth of July Creek mouth which has the largest amount of bank and
overhanging vegetation of the seven food habitat study sites had the
highest percentage use by chinook juveniles of terrestrial insects.
The qualitative investigation conducted has established the primary taxa
utilized by juvenile chinook salmon but has not provided any
quantitative comparisons of habitat and invertebrate communities.To
establish the potential of the mainstem to rear juvenile chinook,and to
determine the possible response of the invertebrate communities to
rnainstem flow alterations,further studies would be required.This data
base would also provide information as to the possible effects that
mainstem flow alterations may have on aquatic invertebrate communities
in the slough environments.
2.1.2.2.4 Other physical and biological constraints
The distribution and abundance of juvenile chinook salmon is undoubtedly
influenced by many other parameters,both physical and biological,
Predation by other fish,such as Dolly Varden and burbQt,may
effectively restrict their distribution into areas of heavy cover
because of behaviroal avoidance of these predators.They may also
compete for food resources with other species,such as sculpin or coho
juveniles.Preference for overhead cover,may be related to predation
by terrestrial predators,such as Arctic terns,gulls,or king fishers.
27
2.2 Coho salmon
Coho salmon,also known as silver salmon,support a substantial sport
fishery in the Susitna River and contribute to the upper Cook Inlet
commercial fisheries.Each of the freshwater phases of the life cycle
of this species that occurs in a portion of the Susitna basin that may
be affected by the proposed hydroelectric project is discussed in the
following narrative.Figure 2-5 depicts the periodicity of the various
life stages in macro-habitat areas that have been identified in the
system.
2.2.1 Adult phase of life cycle
Migration of adult coho salmon into the Susitna begins in the middle of
July and continues through September.
2.2.1.1 Adult harvest by sport and commercial fisheries
Before entering the Susitna River,coho salmon are harvested by the Cook
Inlet commercial fisheries.They are also harvested by a sport fishery
within the Susitna River drainage.The adult coho may be the most
sought after of the anadromous sport fish,with the exception of chinook
salmon.The harvest estimate of coho is illustrated in Figure 2-6.
This figure indicates substantial increases in the commercial harvest in
recent years.
28
~fCOHO·"I~..·l!!~.·II~~J~~~J~~~~~..~~..~-~.~a.-.Ik';:-~~~C~0~C,~...SpeculationbaaedonInfwenc..fromexl.tingdataM·Main.temaSidechanne'.S"SideSlough.SUaUplandSICUQh.-rM-Tributarie.andTributaryMouth.TilSUS'M•TilSUS'M•Til•SUS'MTilsuS'MNoUseTotallyDependentGl0CCHeavy-Us•....00-E-•»Mod.ate-U..cCIa:::-0Rar.()(N>CLillI.Uee•.0~.=AdultMigrotionSpawningaIncubationRearingJuveniles0+ReorinoJUY8niles1+andOlderFigure2-5.Seasonaluseofmacro-habitatbycohosalmonabovetheChulitnaRiverconfluerce(RM98.5).DatasunmaryfromADF&G(1983a,1983b).
500
450
400
~o
aw
I-en 300w>
It:
oot:r
:ren
......250......
0
enaz
ooten
~
~20
I-
150
100
UPPER COOK INLET HARVEST
(Include.non-Suaitno atockal
---SU8SISTENCE·TYONEK
EAST SIDE SPORT FISH
---.----WEST SUSITNA SPOftT FISH
-_.•-•.•-TOTAL SPORT FISH
~
Ol+--r-...--r--.-...,.----,r---r--r-...,.-"'T'"".....,r--""'T"-~__r-"'T'""__..__...,....-......_r-,....._T-~-.__
1%0 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 90 81 82 1983
YEAI'
Figure 2-6.Harvest summary of Cook Inlet and Susitna River coho
sa lmon stocks.Harvest data from ADF&G (198lf)and
K.Florey (Personal communication,ADF&G,Anchorage),
subsistence catch data from Foster (1982)and sportfish
catch data from Mills (1982).Data from 1982 are
prel iminary.
30
2.2.1.2 Adult escapement
The escapement of adult coho salmon into the Susitna is probably the
lowest of any of the Pacific salmon species,but a complete estimate is
not available.The escapement estimate that was made with Peterson
popul ati on estimates at the Sunshi ne,Talkeetna,and Curry stati ons
during the 1982 season is shown in Figure 2-7.The numbers depicted
indicate the number of fish passing the capture site fishwheels,but not
necessarily the total spawners that escape above these sites.An
estimate of 36,800 coho in 1981 and 79,800 in 1982 in the Susitna River
was made by combining the Yentna sonar counts with the Sunshine Station
Peterson estimate.This estimate excludes the tributaries between river
mile 6 and river mile 77 with the exception of the Yentna River.
2.2.1.3 Habitat and environmenta·1 parameters associated with the
adult phase of the life cycle
The most obvious factors which influence the success of coho spawning
are the discharge and temperature of the mainstem Susitna and of the
natal tributaries.As with chinook salmon,the behavior of coho during
natural vat'iations in discharge and temperature of the mainstem may
provide insight lnto what may occur if ihe dam were constructed.
31
COHO
5
~
•
[[llJ
Bj.."......
~.:.:.
•
Estimated Total Sportflah
Harvest of the SUlltna River
Escapement Ettimatfon by Sonar
Counts at the Ventna Station
Petersen Population Estimates
at Sunsh lne Station
Petersen Popu lotion Estl mate,
at Ta Ikeetna Stat Ion
Petersen Population Est Imates
at Cu rry Stat Ion
40-
:I:en-lL.
lL.30
0
en
0 20Z
<!en
::>
0 10:I:....
0
Figure '1.-7.
YEARS
Summary of the population estimate and sportfish
harvest for adult coho salmon within the Susitna River.
Sportfish harvest data from Mills (1982)and escapement
and population estimates from ADF&G (1983a).
32
2.2.1.3.1 Discharge,water quality,and temperature relationships
with adult salmon migration
The discharge and temperature data collection was described previously
for chinooks.The plots of mean daily discharge and temperature arc
plotted against the movement of coho salmon in Appendix Figure B-2.
Within the natural variations in temp~rature,no effect on coho
migrations was observed during 1982.The influence of discharge on fish
behavior is apparent at the higher discharge levels.An inverse
correlation exists when peak flows occurred during migration.Peak
flows also caused a decrease in temperature.This relationship was
observed during the 1981 coho migration as well and similar effects have
been observed with the other species.Within the range of flows that
occurred during the migration,no influence on the behavior of the fish
at the lower end of the flow regime was observed.
Coho salmon have not been observed during 1981 and 1982 passing through
lower Devil Canyon.Passage of fish into the mouths of clear \'Iater
tributaries,Indian River and Portage Creek,has been examined in more
detail (Trihey 1983).By examination of the stream mouth gradient and
associated water velocities and the distance that such velocities are
likely to occur under alternative flows of the mainstem Susitna,pre-
dictions of the influence of mainstem flow on tributary passage of coho
salmon can be made.Trihey concluded that salmon passage into the
tributaries is not likely to be affected,regardless of the flow of the
mainstem Susitna.
33
Coho often use the smaller tributaries for spawning in addition to the
major tributaries.Gash Creek,a small tributary near river mile 111.6,
has had significant numbers of spawning coho during 1981 and 1982.This
creek flows through a culvert under the Alaska Railroad.Dewatering of
the side-channel during very low flow periods could potentially block
access.This poteY1tial has not been quantatively examined yet.Lower
McKenzie Creek and Whiskers Creek also have substantial numbers of coho.
Substrate stability at the mouth of these streams has been addressed by
studies by Rand M Consultants (1982).
Possible influences of dissolved gas supersaturation on salmon adults
migrating into Devil Canyon has been discussed previously under chinook
salmon and is not repeated here.
Habitat requirements associated with spawning have not been established
for this species because minimal spawning is associated with areas
influenced by the Susitna mainstem.This observation suggests there are
1 imitations to spawning cohos in sloughs and the Susitna mainstem.
Temperature,substrate,velocity,and depth at areas used by spawning
coho in some of the clear water tributaries can be incorporated into an
analysis that will provide an estimate of the potential for side channel
areas of the Susitna to support post-project coho spawning and
incubation.
34
-
-
2.2.1.3.2 Other factors that influence the spawning success of
coho salmon
The limitations to spawning of coho salmon in the Susitna basin Clbove
the Chulitna River confluence are not totally known.The influence of
turbidity on the selection of redds,the suffocation of redds by
suspended sediment,and the cover or depth requirements to provide cover'
from predators,may all limit the ability of the mainstem Susitna to
support coho salmon spawning.Ice processes must be a major concern.
During the ice formation process,channels can become dewatered and bed
scouring may occur in isolated areas.Intragravel temperatures may vClry
greatly in a short period of time and may adversely affect egg or alevin
survival.An understanding of the effects that ice processes have on
flow patterns in potential spawning sites and on winter thermal
characteristics is essential to define limits to spawning under current
flow conditions or under regulated conditions.
2.2.2 Juvenile rearing and migration phases
Coho rearing is often associated with habitats that are affected by
mai nstem Sus itna di scha rge,turbi di ty,and temperature.The focus c+
the 1981 and 1982 juvenile anadromous studies has been on determ"ining
the relative abundance and general habitat types associated with the
rearing of this and other anadromous species.The general distribution
data have been used to select specific sites for more detailed
investigations regarding habitat suitability for juvenile salmon and
for measuring the response of these habitat areas to changes in mainstem
35
discharge.This has provided the first step in assessing the response
of juvenile salmon to incremental alterations in flow.
2.2.2.1 Relative abundance of juvenile coho salmon
Juvenile coho salmon probably emerge from the gravel in their natal
clear water tributaries in March or April.From this time until they
outmigrate into Cook Inlet,they are actively feeding and are dependent
upon suitable habitat for rearing.Age (0+)coho apparently spend the
first two months after emergence in the vicinity of their natal areas
(Morrow 1980).They apparently begin redistributing downstream shortly
after this initial period and are collected in small numbers at habitat
sites associated with the mainstem Susitna (Figure 2-8).Rearing by the
young of the year also occurs within the clear water tributaries with
significant numbers present until late fall.At this time,apparently a
substantial portion of the populations outmigrates into the mainstem
Susitna.From this period until May of the next year,some of the
juveniles that originate in Portage Creek and Indian River and other
clear water tributaries are dependent upon habitat conditions in the
mainstem Susitna.
Age 0+fish were collected at the outmigrant trap throughout the summer
with a larger portion captured in the fall,when compared with the other
species.This probably reflects a general redistribution into rearing
areas in sloughs and tributary mouths or small backwater areas
throughout the system.The Age 1+and 2+fish made up 15.2 percent of
the popul ation outmi grati ng duri ng the peri od that the trap was in
36
'---------17-0 0 0 0 0 CJ 0 0
.,."
.1.Portage Creek
2.Slough 21
3.Slough 20
4.Slough 19
5.Indian River
6.Slough 11
7.Fourth of July Creek
8.Slough 9
9.Slough SA
10.Lane Creek
11..Slough 6A
12.Whiskers Creek
13.Birch Creek
14.Sunshine Creek
15.Rabldeux Slough
16.Whitefish Slough
17.Goose Creek
I
OEVIL CANYON
,jUNE,,jULY AUG.SEPT.
I 1I I "II I n:I II
1-0 -00 0-00
Z-O 0 00 00 003-0 0 00 00 00
4-0 0 00 00 005-0 0 00 00 00
a-O 0 00 00 00
T-0 0 00 00 fjO
8-0 0 00 00 00
9-00 00 00 00
10-0 0 00 00 fjfj
11-0 ..Ofj 00 fjfj
IZ-O 0 00 00 ~O
Relative Abundance Key
o Absent 0oTrace1to 10
..Present 11 to 71
•Abundant 72 +over
-No sample
13-fj •.~~O ~O
14-."••fjO 00
15-- •••fj It 0
16--0 0 0 0 0 0 0
Figure 2-8.
----------_.---',.•..
The seasonal variation in distribution and relativE
abundance of coho salmon juveniles at DFH sites on the
Susitna River,lJune through September,1982."Taken
from ADF&G (1983b).
37
place.The outmigration of these older fish was considerably more
regular throughout the summer than other species of salmon (Appendix H).
The trapping efforts that occurred at sloughs and tributaries during the
1981 and 1982 open water seasons indicated a substantial difference in
catch rates between the years.Thi s fa 11 owed a simi 1ar pattern for
chinook juveniles;possible hypotheses as to the cause were discussed in
the chinook salmon section.
Variations in the distribution of coho fry within the specific habitat
sites and possible causes dre addressed in the following section.
2.2.2.2 Habitat and environmental factors associated with the
juvenile phase of the life cycle
The juvenile coho habitat utilization was investigated during 1981 and
1982.During the 1981 field season,habitat data collection was coupled
with the collection of distributional information identical to that
described for chinook (ADF&G 1982).
The analysis of this data is presented in Appendix F for all juvenile
salmon and is used as the basis for the following discussion on coho
salmon.
38
-
-
-
2.2.2.2.1 Physical habitat conditions of rearing juveniles
Discharge (velocity and depth)relationships and their effects on
indices of available habitat.
The studies addressing the response of juvenile coho to mainstern dis-
charge changes were similar to those for chinook juvenile studies.The
reach of river above the Chul itna confluence was investigated using
designated habitat locations at the mouths of tributaries and sloughs
that had relatively high catch per unit effort rates during the 1981
investigations.Five other sites were selected in the reach of river
below the Chul itna confl uence.These were primar"ily based on hi gh catch
rates during the previous season and the logistical convenience of
sampling.The response of the physical habitat component has been based
on the Gold Creek gaging station of the U.S.G.S.for the upper reach of
river and the Sunshine station for the lower.
The effects of mainstem discharge on coho salmon juvenile rearing
habitat at Sunshine Creek and Side Channel,Birch Creek and Slough,and
Lane Creek and Slough B are illustrated in Appendix Figures F-7,F-8,
and F-9.The habitat response to discharge is limited to the study area
defined in Appendix E at each of these study sites.
The definition of habitat used in the ~bove example limits the literal
interpretation of the figure as actually representing lost habitat.
With coho salmon,we observed that the distribution of the fish within
the backwater zones i nfl uenced by the ma i nstem was si gnificantly lower
39
than areas not backed up by the mainstem.Therefore,the projected
changes in habitat as reflected by Appendix Figures F-7, F-8,and F-9.
increase with the decreasing backwater zone.
This has provided (\very general method of estimating the loss or gain
of habitat used by juvenile coho.The advantages of this method include
requiring a relatively low level of resources so a relatively large
number of sites can be sampled.The evaluation of habitat value at a
particular site is estimated based on the actual observed distribution
of fish at the sites.This el iminates the problems associated with
distribution being influenced by other factors such as migration,
proximity to natd 1 areas,etc.The biggest di sadvantage of thi s ap-
proach for coho is that micro-habitat changes within the zones that
occur with flow will not provide any effect on the habitat availability
indices calculated.Observations of the effects of discharge on avail-
able cover and the apparent dependence of coho salmon on this cover
suggest that this component of habitat may be an important factor that
affects the distribution of juvenile salmon.
Water quality and thermal relationships
The water qua 1ity parameters studied,with respect to juveni 1e coho
distribution,included dissolved oxygen,conductivity,pH,and
turbidity.During the open water season,temperature and turbidity are
probably the main factors that influence the distr"ibution of juvenile
coho.
40
-
Temperature affects the basic metabolism of these species;warmer water
frequently acts as an attractant to these fish.This may also be d
factor in the densities of juvenile coho observed in sloughs that have
warmer temperatures during the winter months because of groundwater
influences.
Turbidity may also affect the distribution of the species,providing
cover from predation,but also limiting primary production,food
availability and probably feeding efficiency.Coho salmon juveniles
appear to be found in clear water as opposed to turbid areas and were
most abundant in clear water tributaries.The tributary mouth habitat
with low velocities created by morphological pools or by backed up water
from the mainstem,often had substantial numbers of coho juveniles when
there was available cover in the form of emergent vegetation.If cover
was low in the lower pools,concentrations were often found in the
faster water of the tributary upstream of the mainstem influences.
Since cover was not taken into account in the analysis of the habitat
indices,the preference for the portions of the study sites that did not
have water backed up from the mainstem was the dominant influence on the
habitat values projected (Appendices F and G).
2.2.2.2.2 Timing of outmigration from the tributaries,sloughs and
mainstern and its relationship to environmental changes.
The timing of outmigration and the factors that influence outrnigration
have been of much interest in the Susitna system.Factors influencing
41
----------_..-.--_._....
coho salmon outmigration are probably similar to those listed for
chinook salmon.
There are some data available that indicate that juvenile coho salmon
may outmigrate earlier if densities are higher and if winter development
rates are higher (Hartman et al.1982).The Y'ate of outmigration of
juvenile coho in 1982 had statisticany significant but modest
correlations with the daily mainstem discharge measurements at Gold
Creek (Appendix H).Juvenile coho salmon outmigration was more evenly
distributed than other species throughout the period the outmigrant trap
was operating.The response of this species to short term peak
discharge before sufficient fresh water growth occurs has suggested to
other investigators possible value in regulating flow (Hartman et a 'I •
1982).The size of the individual and behavioral response to
photoperiods may be less important in controlling outmigration than for
the other species of salmon (Hartman et al.1982).
2.2.2.2.3 Food supply for rearing juveniles and its relationship
to other parameiers and preference dependency of species
in the system.
The 1982 studies initiated an investigation of the selectivity of
rearing coho juveniles for aquatic invertebrates at slough and tributary
mouths as was described for chinook.
The food habits of the coho were similar to the chinook salmon described
earlier with minor differences observed between the species.The
42
-
general level of resolution of this study did not a"'low association of
invertebrate communities with micro-habitat.The invertebrate com-
munities \'Jere different among the sites studied but did not follow a
consistent pattern.
The qualitative investigation conducted has established the primary taxa
utilized by juvenile salmon but further studies would be required
to provi de any quantitative compari sons of habitat and i nvertebra~e
communities to mainstem flow alterations.Relating food availability to
juvenile coho requirements would also require additional investigation.
2.2.2.2.4 Other physical and biological constraints
As with the other salmon juveniles,the distribution and abundance of
juvenile coho salmon are undoubtedly influenced by many other
parameters,both physical and biological.Predation by other fish,SLch
as Dolly Varden and burbot,may effectively restrict their distribution
to areas of heavy cover.They may also compete for food resources with
other species,such as chinook juveniles,which may in turn affect to
their micro-habitat preference (Hall and Knight 1981).
Preference for overhead cover may be related to predation by avian
predators,such as Arctic terns,gulls,and kingfishers.
43
2.3 Sockeye sa 1man
The sockeye salmon,also referred to as red salmon in Alaska,is the
most important commercial salmon species in the Cook Inlet area.It
also contributes to an important sport fishery.The distribution of the
fish species by life history stage in macro-habitat areas that have been
identified in the Susitna River drainage is depicted in Figure 2-9.
This report discusses the fresh water phases of the sockeye salmon's
1 ife cycle that occur in the portion of the Susitna basin that may be
affected by the proposed hydroelectric project.
2.3.1 Adult phase of life cycle
In Cook Inlet,two distinct migrations of sockeye salmon can be
observed.An early migration that begins in June is followed by a ,July
migration.The early migration was thought to be primarily associated
with the Kenai River,but 1982 studies on the Susitna River identified a
small early migration into the Talkeetna River drainage.The commercial
harvest of the Susitna stock is primarily directed at the late run which
is the larger of the two.
2.3.1.1 Adult harvest by sport and commercial fisheries
A summa ry of the sport and commercial harvests is presented in Fi gure
2-10.Overall commercial harvests have increased in recent years,
suggesting improved escapement of parent stock or improved environmental
conditions.Sport fishing on the Susitna River for sockeye does occur
44
SOCKEYETotollyDependent••SOlculationbaudonInt.lnee,frOlll1.',tinQdataM·Main,tlmaSid.chonnll,S··SidlSlouQh'SUaUplondSlouQh,r-.Tributori.,andTributaryMouth,NoUseRaftorLittleUteQl>llIad.ateUnQlUCoHeoyytUseoQ.E...oCIn::-o+:>:fJ1"OcAdultMiqrotionSpawningaIncubationRearingJuveniles0+Reorill9Juveniles1+Figurp2-9.Seasonaluseofmacro-habitatbysockeyesalmonabovetheChulitnaRiverconfluence(RM98.5).Datasummaryfrom~DF&G(1983a,1983b
----UPPER COOK INLET HARVEST
(Includ.,non-Su,ilna .Iock,)
----SUBSISTENCE-TYONEK
----EAST SIDE SPORT FISH
--------WEST SUS/TNA SPORT FISH
--••-•.•-TOTAL SPORT FISH
400
800
1200
2000
2400
o
LU
~1600
(I)
LU
~
<
:I:
:I:
(I)
i:i:
LLo
(I)az
oct
(I)
::>o
:I:
~
6
4
2
\
!
\
\/
\./I'-~/"'..,J,-,\..,"""""...,'
,I
\._---,I,'"....."".,,'
........
........_-
O+---,.-...,...........,..-.,.----r-.,.----r-.,.---r-r--r-,...-"""T'"-r-"""T'"-r--"""T'"--,r-.....,---,r-.........,~
1960 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 1982
YEARS
Figure 2-10.Harvest summary of Cook Inlet nnd Susitna River sockeye
sa lmon stocks.Harvest data from ADF&G (1981f)and
K.Florey (Personal communication,ADF&G,Anchorage),
subsistence catch data from Foster (1982)and sportfish
catch data from Mills (1982).Data from 1982 are
preliminary.
46
-
-
but the catches are not large when cOl:npared with those of the other
species.
2.3.1.2 Adult escapement
An estimate of the adult sockeye salmon escapement into the Susitna
River is not available.An escapement estimate has been produced from
the 1981 and 1982 Su-Hydro surveys by combining the sonar counts of the
Yentna River with the Petersen estimates of Sunshine sampling station.
This estimate of 265,000 sockeye in 1982 and 273,000 in 1981 excludes
the tributaries,except the Yentna River,below Susitna river mile 77
and above river mile 6.Petersen estimates of the escapement for the
other sampling stations are depicted in Figure 2-11.This demonstrates
a marked reduction in sockeye salmon numbers in the Susitna above the
Chulitna River confluence.
2.3.1.3 Habitat and environmental parameters associated with the
adult phase of the life cycle (upstream migration,
passage and spawning).
During the upstream spawning migration,sockeye salmon are influenced by
environmental variables that m~y ultimately affect their spawning
success.The sockeye escapement in the upper Susitna above the Chulitna
confluence is primarily into sloughs with perhaps a small number running
into the Chase Creek drainage.As with other salmon species.sockeye
may be influenced behaviorally by discharge and water temperature
conditions of the mainstem Susitna.
47
E.timated Total Sportfish
Harve.t of the SUIltna River
Escapement Eltlmation by Sonar
Counts at the Ventna Station
Petersen Population E.timates
at Sunshine Station
Petersen Population Estimatn
at Talkeetna Station
Petersen Population Estimates
at Cu rry Stat Ion
SOCKEYE
~•
[[]]
r.:B~
•300
400
10
0-+--------.................
::I:.100
(f)
LL
l.Lo
(f)
oz«
(f)
::lo
::I:
t-
YEARS
Fi ~ure 2-11.Summary of the population estimate ond sportfish
harvest for adult sockeye salmon withi n the Sus i tna
River.Sportfish harvest data from Mills (1982)and
escapement and population estimates from AOF&G (1983a).
48
2.3.1.3.1 Discharge,water quality,and temperature
relationships with adult sockeye salmon migration
-
-
The timing of sockeye salmon migrations in the Susitna River have been
compared with temperature and mainstem discharge,similar to that
presented earlier for chinook and coho.These movements are illustrated
in Appendix Figure B-5 and the analysis is described in Appendix B.lhe
peak of the sockeye migration in 1982 was inversely correlated with
di scha rge.The movements appea r to decrease as di scharge increases and
increased movement occurs as discharge decreases.
Access to tri butari es is not a major factor for sockeye salmon with
perhaps the exception of Chase Creek.Although escapement was not
documented in Chase Creek in 1982,earlier studies (ADF&G 1974)
documented sockeye salmon spawning in this drainage.The problems of
access into the smaller tributaries at lower mainstem flows is addressed
by a report by R&M Consultants (R&M 1982).
Since the spawning of this species occurs almost exclusively in slough
habitats in the Susitna River above Talkeetna,most of the analysis has
concentrated on the effects of discharge on passage and the availability
of spawning habitat in these sloughs.
Passage into the sloughs of the upper Susitna is addressed in Appendix
B,which also outlines the methodology used to develop passage
estimates.For sockeye salmon adults,passage into Sloughs 11,8A,and
49
-----_._.._.----
21 appears most critical because they had the highest observed counts of
sockeye during the spawning period.Sockeye were also found in Moose
Slough,Slough B,Slough 8B,Slough 9,Slough 8C,Slough 9B,and Slough
9A.The effect of discharge on salmon passage into sloughs is described
in Appendix B and is summarized in Appendix Table B-2.
In addition to passage into sloughs,the availability of suitable
spawning conditions has been evaluated for Sloughs 8A,21 and 9.By the
use of IFG-IV models,an analysis of the physical habitat under variable
flow conditions has been produced in Appendix D.
Although information is available on the physical habitat,the analysis
has not yet included usage by sockeye salmon because of limited data.
Suitable discharge and temperature conditions during other phases of the
life cycle must also be considered in addition to adequate passage and
spawning conditions.Optimal passage and spawning conditions may
provide very little benefit to the freshwater production of sockeye
smolts if incubation and rearing are the major limits on production.
These other factors are addressed in the following discussion.
2.3.1.3.2 Substrate type associated with spawning
Substrate qual ity and quantity may be critical factors for successful
spawning and incubation (Cooper 1965 as cited in Bell 1980).The
stability of the substrate after spawning also has to be considered.
Because of the possible critical nature of the substrate for successful
reproduction,adult sockeye probably have behavioral instincts to select
50
substrate suitable for successful reproducti on.Appendi x C addresses
the substrate preferences by chum and sockeye salmon at selected
sloughs and their tendency to key on areas of upwelling.
These data can be used in future analysis of the potential of other
non-slough habitats for enhanced production of sockeye and can be also
used in further analysis of the effects of high water on substrate
stability in these sloughs.
An important factor whi ch is not addressed in these studi es is the
effect of suspended sediment on the substrate.The deposition of
suspended sediment on the gravels used by the spawning sockeye has been
documented to adversely affect survival of incubating embryos,generally
by suffocation (Iwamoto et a1.1978).Substrate used by the spawners,
needs to be periodically cleansed by highwater velocities to remove the
deposited sediments.However,if the velocities become excessive,the
gravel can be completely washed out,and suitable spawning substrate
will be replaced with a larger bed material which is unsuitable for
spawning.
-2.3.1.3.3 Other physical and biological constraints on
spawning success
During spawning,other factors can become significant in reducing
spawning success.The lower end of the discharge that provides
sufficient passage and adequate habitat conditions for spawning,may not
51
---------_._-"--_._-"""
be sufficient for protection from predation by bears or predatory birds.
Although not possible to quantify under the constraints of this study,
low flows could potentially reduce spawning success.
2.3.2 Incubation and emergence phase of life cycle
The incubation of sockeye salmon eggs after spawning and the subsequent
emet"gence of juvenile sockeye from the gravel encompasses the period of
time from early September until lJune of the following year.Ongoing
investigations will provide more data on timing of egg incubation and
emergence and will be included in a winter report summary.An
additional controlled study of the effects of temperature on sockeye egg
incubation is being undertaken by the U.S.Fish and Wildlife Service.
Important effects of ma i nstem di scharge on incubati on and emergence
include the possible disruption of redds by fall floods.Scouring flows
after sockeye eggs are depos ited in the gravel can be expected to
severe ly decrease survi va 1 of the redds.The effects of ice processes
during the fall and winter can also be quite adverse.Initial
observations of winter mainstem flow through Slough 8A,indicates that a
sudden and prolonged decrease in temperature occurred and the
developmental rates of juveniles were delayed.An apparent increase in
egg mortality may also be related to this event.A more complete
analysis of egg incubation processes will be included in the 1982-1983
winter report.
52
2.3.3 Juvenile rearing and migration phases
The reari ng phase of sockeye juveni 1es in the Sus itna Ri ver above the
Chulitna River confluence has been puzzling.Although substantial
numbers of sockeye adults consistently return to selected sloughs above
the Chulitna River confluence,juvenile rearing above the confluence has
been difficult to document.Since sockeye are plankton feeders and most
frequently rear in lake environments,similar types of habitat were
thought to be required for successful rearing of this species.Analysis
of the adult sockeye scales and the operation of an outmigrant trap has
provided the bu"1 k of the evidence as to the nature of the juvenil e
sockeye rearing but major questions still remain.
2.3.3.1 Relative abundance of juvenile sockeye salmon
During 1982,the use of beach seines and electrofishing gear provided
some information on the distribution of sockeye juveniles.Sockeye were
collected at all of the sixteen sampling sites between Goose Creek and
Slough 21 during the summer (Figure 2-12).With the exception of a
small number of Age 1+juveniles collected at Slough 6A,these sockeye
were all young of the year (Age 0+).The outmigrant trap,which began
operation on June 18,provided more specific results.The Age 0+
juveniles were collected during the surr~~r period with peak catch/hour
occurring during the second week in July.Less than 3 percent of the
juvenile sockeye collected at the smolt trap were Age 1+.
53
-----------,-----
-----17--()0 -.G __(if (if 0
-G fi 00__(if ..
-.J
-8
u
16--
CANYON
JUNE JULY AUG.SEPT.
1:II r II I II r II
1---
2--•__0 ..0 __0
3--0 fifi fiO 00
-4--il -fi __0 00e--0 00 fiO o -
e--fi Ofi 00 fiO
7--0 Ofi 00 00
8-0 fi fifi 00 fiO
9-fi fi --.fi __fiO
JO-0 fi 00 00 "fi11-."••"fi __
12-0 fi-00 00
Relative Abundance Key
o Absent 0
fi Trace 1 to 100
•Present 100 +over
-No sample
13-fi fi __fi 0-00
14-0 0 o -0 __o -
1.Portage Creek
2.Slough 21
3.Slough 20
4.Slough 19
5.Indian River
6.Slough 11
7.Fourth of July Creek
8.Slough g
9.Slough 8A
10.Lane Creek
11.Slough 6A
12.Whiskers Creek
13.Birch Creek
14.Sunshine Creek
15.Rabideux Slough
16.Whitefish Slough
17.Goose Creek
Figure 2-12.The seasonal variation in distribution and relAtive
abundance of sockeye salmon juveniles at DFH sites on
the Susitna River,June through September,1982.Taken
from ADF&G (1983b).
54
The analysis of adult sockeye scale patterns suggests that they are
rearing in freshwater during their juvenile life phase.The majority of
the returning adult sockeye salmon outmigrated at Age 1+,thus
indicating two summers of growth in freshwater.In addition,scale
pattern analysis of upper Susitna sockeye did not find that these stocks
were significantly distinguishable from stocks of the Chul itna or the
Talkeetna drainage (Bernard et al.,1983).Based on the assumption that
no fry rear above Curry Station,the authors suggested that these fry
most likely die or move to areas in the Susitna River below the Chulitna
confluence to rear.
The movement of Age 0+sockeye monitored by the outmigrant trap and the
limited numbers of juveniles collected at first appears to support this
hypothesis.However,substantial numbers of rearing juveniles may have
outmigrated by the time the outmigrant trap was installed (June 18).
Further,the collection of Age 0+juveniles in the outmigrant trap
indicated continual growth during the summer.The food habits
investigation indicated active feeding of juvenile sockeye in the
sloughs during the summer with planktonic forms in addition to larger
insects being used.
Finally.initial observations of outmigration during the spring of 1983
at Slough 11 suggests a significant number of Age 1+sockeye are
present.The viability of this stock will best be resolved through
monitori ng the returns of the coded wi re taggi ng program currently in
progress.Because the monitored populations of Age 1+sockeye are small.
it is questionable that studies of sockeye r'earing in the lower river
55
would provide any definitive results,but the analysis of scale patterns
and the frequency of the coded wire tagged returning adults should
resolve this issue.
2.3.3.2 Habitat and environmental factors associated with the
juvenile phase of the life cycle
Assuming that the juvenile sockeye are rearing successfully in the upper
Susitna drainage,it is important to determine how this population
responds to changes in their physical environment.The following
di scussi on addy'esses primarily the di stributi on and associ ated habitat
of the Age 0+sockeye in the study areas investigated during the 1982
field season.
2.3.3.2.1 Physical habitat conditions of rearing juveniles
The 1982 sampling program was designed to provide distributional data on
sockeye juveniles and to identify factors that affect their
distribution.The rationale for the development of the study design has
been described earlier for chinook salmon.The sampling program for
juvenile sockeye was also designed to determine the areas where this
species reared.Previous years studies provided little distributional
information,primarily because of the limitations of the collecting gear
used.The analysis of juvenile sockeye habitat data presented in
Appendix F is used as the basis for the following discussion.
56
Discharge (velocity and depth)relationships and their effects on
indices of available habitat
The effects of mainstem discharge on juvenile sockeye salmon rearing
habitat in Slough 8A,Birch Creek and Slough,and Slough 19 is outlinea
in Appendix F,and illustrated in Appendix Figure F-10,F-11,and F-l?
The habitat response to discharge is limited to the study areas defined
in Appendix E at these sites.
The pattern of catches observed indicates that the juvenile sockeye
preferred low velocity areas and were most often associated with the
backed up area of the mainstem Susitna.Frequently,the concentrations
of juvenile sockeye were near their natal sloughs.An important
exception was Slough 6A which did not have any sockeye spawning and
consistently provided habitat for rearing juveniles.This slough has
relatively clear water,is heavily vegetated around its perimeter,and
has no limitations on access.The presence of high concentrations of
juvenile sockeye in this slough suggests that access into sloughs by
rearing juveniles may be an important factor affecting their survival.
The Appendix F analysis has provided a very general method of est-irnating
the loss or 9a in of habitat used by juvenile sockeye.The advantages
and disadvantages of this method have been previously described for coho
and chinook salmon and will not be repeated.
57
Water quality and thermal relationships
The factors which dominate the distribution of sockeye salmon are
probably temperature and turbidity within the sloughs,-in addition to
the hydraul ic parameters discussed earl ier.Slough 6A,where the head
is rarely,if ever,breached,had large concentrations of juvenile
sockeye.Slough II,where the head rarely breaches,also had
significant numbers of rearing sockeye.Assuming slough rearing sockeye
have similar requirements to their lake rearing relatives,the low
velocities and low turbidity levels of sloughs where the heads are not
open to the passage of mainstem water may be important prerequisites for
successful rearing.
The water quality parameters studied,with respect to juvenile sockeye
distribution,include dissolved oxygen,conductivity,pH,and turbidity.
Turbi dity provi des cover from predati on and 1 imi ts primary production,
food availability,and probably feeding efficiency.Areas with low
velocities created by morphological pools or by backed up water from the
mainstem,often had significant numbers of juvenile sockeye.Since
cover was not taken into account in the analysis of the habitat indices,
the preference for the portions of the study sites that had water backed
up from the mainstem was the dominant influence on the habitat values
projected.
58
2.3.3.2.2 Timins of outmigratiorl from tilt'frH",utdrlt::s"s101.jh:,dt;J
mainstem and its relationship to environmental changes
Factors affecting the outmigration of sockeye salmon juveniles can be
quite complex.Immediately after emerging,sockeye juveniles generally
redistribute into rearing habitat.This redistribution behavior is
apparently genetically controlled (Brannon 1972).Juvenile sockeye
apparently also pass through a period of time when they are able to
successfully smolt.If retained in freshwater past their migration
time,their response to the presence of salt water may again resemble
that of freshwater fish and they can remain land locked (Foerster 1968).
Outmigration of juvenile sockeye from lakes is also affected by
temperature (Foerster 1968).
Outmigrant data did not demonstrate any dramatic response of sockeye
juveniles to mainstem environmental variables tested but a positive
correlation with discharge changes was apparent (Appendix H).The
temperature changes that occur in the mainstem Susitna in the sprinq
were largely completed when the monitoring of outmigrants began in 1982.
Other factors which may influence the smolting and outmigration process
have been previously discussed for chinook and coho and w6uld generally
apply to sockeye as well.
59
----_..,-----"-_._..._--_.......•__.__._----------
2.3.3.2.3 Food supply for rearing juveniles
Rearing areas and food supply is probably the limiting factor in
production of sockeye salmon in slough environments of the Susitna
River above the Chul itna confluence.Sockeye are generally considered
lake rearing species although slough populations are not uncommon
(Foerster 1968;McCart et al.1979).Recent studies (McBride 1983)on
the East River near Yakutat indicate large returning runs can occur in
rivers where major returns are from 0+Age outmigrants.This suggests
limited fresh water rearing.Our limited investigation of food habits
i ndi cated that sockeye were feedi ng on an assortment of aquatic and
terrestrial invertebrates but also had significant slough zooplankton in
their diet.The downstream migrant distribution noted by the outmigrant
trap catch rates may reflect displacement into lower river areas in
search of more favorable food suppl ies.The size and growth measured
for the few Age 1+sockeye that were collected was within the range of
growth associated with lake populations in south central Alaska.
2.3.3.2.4 Predation and cover relationships
As with the other juvenile salmon,cover appears to be important for
sockeye salmon.However,schools of Age 0+juvenile sockeye appeared to
be much more visible and their general behavior was not as evasive as
that associated with chinook or coho juveniles.Further study is needed
to quantify effects of cover on the juvenile sockeye distribution.
60
2.4 Churn salmon
The chum salmon.also referred to as dog salmon.is an important
commercial species ·in Cook Inlet with limited use by sport fishermen.
This species makes substantial use of slough habitats for spawning.
Chum salmon also spawn in the mainstem and side channels of the Susitna
River reach above the Chulitna confluence.With the exception of the
even year run pink salmon.it is the most abundant species using this
reach of river.Figure 2-13 depicts the distribution of the various
life stages of chum salmon in macro-habitat areas that have b~en
identified in the Susitna River drainage above the Chulitna confluence.
2.4.1 Adult phase of life cycle
2.4.1.1 Sport and commercial fisheries harvest
The chum salmon adults provide a major component of the Cook Inlet
commercial harvest in addition to a limited sport fishery.A summat'y (1f
the sport and commercial harvests is presented in Figure 2-14.
Commercial harvests have ranged from less than 300,000 to over 1.4
million chum salmon over the past twenty years.The 1982 hat'Vest was
the largest on record for this species in Cook Inlet 1 .The long tern:
average is approximately 700,000 fish.The sport fish harvest is quite
modest,reflecting the rapid decrease in the quality of this species
after it enters fresh water.
I p 1'·dre,m,na ry a ta •ADF&G Region 2 Commercial Fish Division.
61
•·"l1~~""~!"O~!""c"'6"J:>&~,","&a.,"&~~~~":,~;.~~~.:..~"?~.;....~Q.C...~Q.c....?Goc...~Q,~2•0~~•aa~•G~••c:(,rn..,c",cn,cr:..,.,-,c..,cn••Sp.culationbaudonInfwe~sfrom.xlstingdatoM·Mainst.m8Sld.chann.lsS··SideSloughsSUaUplandSloughs~.TributariesandTributarvMouthsTillSuSIMsuITill:rI~f"~~~~2~~I'~i.~~:Ioo~1..·OA3eC-,.,...,C..,(I)CHUM·OlO...··I...·Oltt~:3c!lc:lc5Di':i5I;er-.I~"!-I~~~.;..C:5.?li.C:k?li.li~-'"~oc(~.x~c~rll..,~~.xMS.SuITillNoUseTotallyDependent«)0CCHeavy-U..L-0Q.E-ell>Mod_ate--UseCell0'\a:::N-0RareOf')(LittleUseell"0CAdultMigrationSpawningaIncubationRearingJuveniles0+Fiqure2-13.Seasonaluseofmacro-habitatbychumsalmonabovetheChulitnaRiverconfluence(RM98.5).DatasummaryfromADF&G(1983a,1983b).
Q
LLI
I-
(I)
LLI>0::
et:x:
:x:
(I)
u..
IL
o
(I)
Q
Z
et
(I)
::>o
:t:
I-
1400
10
---UPPER COOK INLET HARVEST
(Illcludn llon-SulilllO Ilockl)
.----SUBSISTENCE-TYONEK
EAST SlOE SPORT FISH
------~-WEST SUSITNA SPORT FISH
-•.•-•••-TOTAL SPORT FISH
,-,°1~96::0~61~~6:-2;6~3;64~-=6r:~-=6!:6-=6:r::7-=6:r.::8-6:r-9-7"'0-"71-""--'I'..,..-r-..-F"~~-:;:-,:,-",-""-=I-=:l:i~-r-
72 73 74 7~76 77 76 79 60 81 82 83
YEAR
Figurt~?-14.Harvest summary of Cook Inlet and Susitna River chum
salmon stocks.Harvest data from ADF&G (198lf)and
K.Florey (Personal communication,ADF&G,Anchorage),
subsistence catch data from Foster (1982)and sportfish
catch data from Mills (1982).Data from 1982 are
pre 1 i mi na ry .
63
2.4.1.2 Adult escapement
An estimate of the escapement of chum salmon into the Susitna River is
not available.An escapement estimate was produced from the 1981 and
1982 Su-Hydro studies by combining the sonar counts at the Yentna River
station with the Petersen estimates at Sunshine station.This provided
an estimate of 458.500 chum for 1982 and 283.000 chum for 1981.This
estimate excludes the tributaries between river mile 6 and river mile 77
with the exception of the Yentna River.
Petersen estimates for each of the sampling sites and the escapement
estimate from the Yentna sonar site are depicted in Figure 2-15.The
numbers of chum passing the Sunshine station are very large,with
approximately 50.000 chum salmon escaping up the Susitna River and its
tributaries above the Chulitna confluence.
64
As with the other species,chum salmon upstream migratory movements can
be influenced by the effects of mainstem discharge.Because this
species spawns in clear water tributaries.sloughs,and some of the
turbid water side channels of the mainstem.a broad array of chum
habitat conditi ons may be affected by ma i nstem di scha rge changes.
2.4.1.3 Habitat and environmental parameters associated with the
adult phase of the life cycle (upstream migration.
passage and spawning)
Estimated Total Sportfish
Harvest of the SUlltna River
Escapement Eltlmation by Sonar
Counts at the Yentno Stat Ion
Petersen Populatian Estimates
at SunshIne Station
Petersen Population Estimates
at To Ikeetna Stat Ion
Petersen Population Estimates
at Cu rry Stat Ion
CHUM
~
iii
[]]
r.p
L:iJ
•400
500
-
300
200
I
(/)
lL.100
lL.tV
0-(/)
0 50
Z
<{
CJ)
:::>
0 40
I
t-
30-
-
-
-
20
10
0-+---_
YEARS
Figure 2-15.Summary of the population estimate and sportfish
harvest for adult chum salmon w~thin the Susitna River.
Sportfish harvest data from Mills (1982)and escapement
and population estimates from ADF&G (1983a).
65
2.4.1.3.1 Discharge,water quality,and temperature relationships
with the adult chum salmon migration
The chum migrations in the Susitna have a minor correlation with dis-
charge;apparently,short duration high water periods cause a decreasE'
in migration rates.This observation is based on both the 1981 and the
1982 data (ADF&G 1982;Appendix B).
Because the mainstem temperature during the chum migration varied
inversely with discharge,the effect of cold water,as well as the
discharge,may be a factor in decreasing upstream migration.
Access into the tributaries for chums is similar to other species and
has been evaluated by Trihey (1983).No access problems at Indian River
and Portage Creek are anticipated under a wide range of flow conditions.
Chum were observed at eight streams above the Chulitna River confluence
in 1982.Portage Creek,Indian River,Lane Creek and Fourth of July
Creek had the largest chum salmon survey index counts.Little Portage
Creek,Skull Creek,Fifth of July Creek,and Jack Long Creek also had
chums present during the surveys.The tributary and the slough index
counts provide only relative abundance of the fish during peak spawning
periods.Absolute numbers or percentage of the escapement using the
different habitat types have not been determined.
Because of the use of sloughs by this species,much of the analysis has
concentrated on passage by adul t chums into these areas (Appendi x B).
66
Chums were observed in 17 of 34 sloughs surveyed in 1982.The greatest
numbers were recorded at Sloughs 21 t lIt 8A,and 9,with over 80 percent
of the slough index counts occurri ng in these areas.The effects of
discharge on access into the sloughs are portrayed in Appendix Table
B-2.
The low water year of 1982 compared with the relatively high water year
of 1981 provides an opportunity to compare the effects of discharge
during the spawning season on index counts in the representative sloughs
and over the remainder of the river in general (Appendix B),The
estimated chum escapement in 1982 was 2.4 times greater past Talkeetna
Station than the 1981 escapement counts.Three-hundred-thirty-four
fewer salmon were counted in the sloughs in 1982 than in 1981,despite
the much larger"total escapement estimate.Tributary streams,not
affected by the low mainstem discharge t had much higher counts in 1982
than in 1981 in the index areas surveyed.
The numbers observed spawning in the sloughs versus the escapement,the
distribution of fish within the sloughs,and their response to the short
term changes in discharge (fish remaining in the sloughs during the
September high water period were able to move further upstream)provide
abundant evidence that some habitat was unavailable and the flows of
1982 had an adverse affect on the success of slough spawning chums.
The effects of discharge on slough-spawning chum salmon have also been
evaluated using the IFG-IV model for three sloughs that were studied
intensively (Appendix D).
67
.....__.._.--_._---------
2.4.1.3.2 Substrate type associated with spawning
Because of the limited range of calibration of the hydraulic modeling,
the analysis is limited to only those conditions that were present when
the data were collected.An examination of substrate availability
versus utilization,in the intensively studied sloughs,is described in
Appendix C.Substrate quality and quantity ultimately affect spawning
success and is probably a major factor in the behavi ora 1 se 1ecti on of
redd sites by spawning chums.The modeling results described in
Appendix 0 suggest a decided preference for certain types of substrate.
As with sockeye,this analysis can be used for determining the effects
of short term flood events on the substrate.Because of accumul ated
sediment,occasional flushing flows may be required to clean spawning
gravels.However,such floods occurring after the eggs are deposited.
may decrease survival.In the case of high flood flows.the substrate
may be removed completely,leaving only armored cobble,unsuitable for
spawning.This information,combined with the other environmental
parameters,should provide an indication as to the conditions that will
be necessary to develop possible mitigation for salmon losses associated
with the project as well as determining potential uses of other segments
of the mainstem Susitna or its side channels under alternative project
flow regimes.
68
2.4.1.3.3 Other physical and biological constraints on spawning
success
Other factors may also 1imit the success of spawni ng chum.As YJith
sockeye,predation by bears,gulls,and eagles will probably increase as
the discharge decreases,because of 1imited cover.Ice processes and
summer floods strongly affect the morphology of the sloughs and side
channels,in addition to affecting substrate stability.These processes
probably remove beaver dams from the sloughs and side channels and help
maintain the spawning conditions at these sites.Virtually all sloughs
that have no upper berm that is occasionally overtopped (upland sloughs)
have very limited or no spawning by chum salmon or other salmon species.
Beaver dams probably create passage problems in addition to causing
local sedimentation and decay in the quality of spawning gravels.The
beaver dams on Slough 8A appeared to create access problems during the
1982 chum migration.
2.4.2 Incubation and emergence phase of life cycle
The incubation of chum salmon embryos extends from deposition of the
eggs 'j n September'to a 1evin emergence from the gravel in mi d-April to
June.The studies of the effects of environmental variables are
currently ongoing and the results will be presented in the upcom'lng
wi nter report.
Initial observations have indicated that winter overtopping of sloughs
may adversely affect i ntragrave 1 temperatures and subsequently retar'd
69
--------_.__._-----
development rates and increase embryo mortality.A parallel laboratory
study on the effects of temperature on development rates is being
conducted by the U.S.Fish and Wildlife Service.
2.4.3 Juvenile rearing and migration phases
The rearing of juvenile chums was first observed in the upper Susitna
slough habitats during the summer of 1982.Our field collection program
provided information on the distribution and relative abundance of this
species which had previously had limited sampling.The first two or
three months after emergence may be spent in freshwater and significant
growth may occur.The amount of fresh water growth may influence long
term ocean survi va 1 and subsequent run returns.The j uveni 1e chum
studies attempted to establish the distribution and outmigration timing
of this species and to determine the influence of mainstem discharge on
habitat quality.
2.4.3.1 Relative abundance of juvenile chum salmon
During 1982,the use of beach seines and electrofishing gear,in addi-
tion to the minnow traps,provided much more information than in 1981 as
to the distribution and relative abundance of juvenile chum salmon.
Chum juveniles were collected at all sampling sites above the Chulitna
River confluence except for Portage Creek.All sites sampled before the
first of July in the reach of river below the Chulitna confluence also
70
had chums present except for Rabideux Creek and Whitefish Slough which
were not sampled until after July 1 (Figure 2-16).
The outmigrant trap provided information on the relative timing of the
outmigration.However,the data suggests that the peak outmigration may
have occurred prior to the installation of the trap on June 18th
(Appendix H,Appendix Figure H-4).Numbers of outmigrants peaked about
the time of installation and rapidly decreased after this time.Compar-
ison of the length of the juveniles collected at the onset of the traps
operation with the juveniles collected toward the end of the obsflned
outmigration,suggests that significant fresh water growth is occurring
above the Chulitna confluence reach of the Susitna.
2.4.3.2 Habitat and environmental factors associated with the
juvenile phase of the life cycle
Juvenile chum spend as much as three months in freshwater,prior to
outmigrating.The rearing opportunities in the Susitna River estuary
may be quite limited because of the high turbidity,thus suggesting that
fresh water rearing in the mainstem Susitna and its sloughs could be
important for this species.These habitats may act as a substitute for
rearing habitat associated with estuaries usually utilized by chum
during their initial growth phases before migration into the deeper
water ocean environments.Although we have limited data which support
this hypothesis,observations of juvenile chums within the slough
environments in the upper and lower portions of the river suggest this
rearing habitat may be very important for the population.
71
----------_..__.-_.,
'---------17-~~0 0 0 0 0 0
a
1 to 100
100 +over
CANYON
o 0 00o0000
.JU\..Y AUG.SEPT.
III in III
Q 0 0 0 0 0
~O 00 00
00 00 00
00000-o -0 0 0 0
00 00 00~O 00 00
00 00 00
00 00 00
00 -0 00
~-oooo
Relative Abundance Key
o Abs£>nt__Trace
•Present
-No sample
le--0
tlS--
-------13-.-~~~~0 0 0
o'l--------14-~0 0 - 0 0 0-
.JUNE
:r l[
1--
z--w
~::=i
6--~
7--~
.-~~
9-~0-----------10-0 "H-:----------tl-•.-
rt------------IZ-~
1.Portage Creek
2.Slough 21
3.Slough 20
4.Slough 19
5.Indian River
6.Slough 11
7.Fourth of July Creek
8.Slough 9
9.Slough 8A
10.Lane Creek
11.Slough 6A
12.Whiskers Creek
13.Birch Creek
14.Sunshine Creek
15.Rabideux Slough
16.Whitefi~h Slough
17.Goose Creek
Figure 2-16.The seasonal variation in distribution an~relative
abundance of chum salmon juveniles at DFH sites on the
Susitna River,June through September,1982.Taken
from ADF&G (1983b).
72
-
2.4.3.2.1 Physical habitat conditions of rearing juveniles
The 1982 sampling program was designed to provide distributional data on
the chum juveniles and to test specific hypotheses as to what factors
influence their distribution.The rationale for development of the
study design has been described earlier for chinook juveniles and
applies equally to the evaluation of the habitat for chum rearing.
Discharge (velocity and depth)relationships and their effects on
indices of available habitat
An analysis of the effects of discharge on the usable wetted surface
areas of selected sloughs and tributary mouths is described in
Appendices E and F.The response of habitat to discharge is limited to
the confines of the study design and the study sites described.These
study locations were selected because of logistical convenience,in
addition to being important for juvenile rearing.
The response of the habitat index to mainstem discharge for chums at
these sites is illustrated in Appendix Figures F-13 to F-15.The
pattern observed at these sites suggests that juvenile chums prefer
lower velocity areas.and are most often associated with the backed up
regions near the mouths of the sloughs and clear water tributaries.The
distribution of chums.during the June and early July samplings,
paralleled that of sockeye salmon so that much of the discussion on
sockeye rearing applies to this species as well.Passage into the
downstream sloughs and backwater areas after the juveniles leave this
73
natal area may be influenced by the discharge and associated stage of
the mainstem.Slough 6A had high concentrations of juvenile chums,even
though minima"1 chum spawning occurred there.As with sockeye juveniles,
this nldY Y'eflect the combination of quality rearing habitat and
efficient passage into these areas.
This analysis has provided a general method of estimating chum juvenile
habitat availability under a limited range of mainstem flows.The
advantages and disadvantages of this method for describing the changes
in habitat availability have been described in the ch-inook juvenile
section.
Water quality and thermal relationships
Water quality may have important effects on the rearing habitat used by
juvenile chum salmon (Appendices F and G).Chum were found in both
clear and turbid water.The concentrations of chum usually followed the
numbers of spawning adults.Slough 6A,which had significant
concentrations of rearing juveniles during June,also has vey'y high
cover,easy access,and non-glacial water,although the tannin staining
provides some cover.Although not quantified,the juvenile chum
appeared to be found in schools in clear water whereas in turbid area
they appeared to be much more broadly distributed as individuals.This
type of behavioral influence has been described for pink salmon in the
Fraser River Estuary in British Columbia (Vernon 1966).
74
Temperature is another habitat component that may ;nfl uence reari n9
habitat.In areas where a thermal contrast occurred,no obvious
influence on distribution was apparent (Appendix F).
2.4.3.2.2 Timing of outmigration from the tributaries,sloughs
and mainstem and its relationship to environmentdl
changes
......
The timing of outmigration for juvenile chum salmon is apparently much
more keyed to the time of year or associ ated dayl ength than with the
other species (Appendix H).The species must migrate to the ocean
within a limited period after its emergence for successful development.
Changes in growth and development may affect this process and the
tolerance of the fish to salt water is affected (Iwata 1982).Access to
the mainstem Susitna may be affected by very low water levels in the
spri ng.Fi sh have occas i ona lly been observed to be trapped in 1and
locked pools.
Data currently available have indicated that at least a portion of the
populations rear in the sloughs of the Susitna and outmigrate during the
first two weeks of June.Insufficient data were obtained to correlate
environmental conditions with the cutmigration of this species.
75
2.4.3.2.3 Food supply for rearing juveniles and its relationship
to other parameters and preference dependency of species
in the system
Only limited observations on the food habits of rearing chum were made.
The few stomachs analyzed from juveniles collected during the 1982 field
season,suggest that the fish are actively feeding and that Chironomids
may be the primary food item (ADF&G/Su Hydro unpublished data).Because
the survival of this species in the Cook Inlet area may be keyed to
fresh water growth.further study of the availability of food sources
and the dependency of chum on these food sources would be desirable.
2.4.3.2.4 Predation and cover relationships
As discussed for the other rearing species of salmon,cover appears to
be an important factor for juvenile chums.This may affect the pre-
dation on juvenile chums.
76
2.5 Pink salmon
Pink salmon,otherwise known as humpback salmon or "humpies",have a two
year life cycles which results in distinct odd and even year runs.In
the Susitna River,the even year run is the strong run;thus,the 1982
season provided an opportunity to monitor various components of the
adult life history.During even years,pink salmon are the most abun-
dant species of salmon in the Susitna River.Figure 2-17 depicts the
distribution of pink salmon in the Susitna by life history stages
associated with macro-habitat areas in the Susitna River basin.
2.5.1 Adult phase of life cycle
2.5.1.1 Adult harvest by sport and commercial fisheries
The pink salmon of the Susitna River contribute to substantial harvests
by both sport and commercial fishermen.A summat'y of the sport and
commercial harvests is presented in Figure 2-18.Harvests of the even
year commercial catch have averaged about 1.6 million with odd year
averaging less than 10 percent of that number.The commercial harvest
fluctuates greatly,even within comparisons of strong and weak year
harvests.Even year harvests have varied from over 3,000,000 to fewer
than 500,000 fish while the odd year has varied from over 500,000 to a
low of 23,000 fish.
The sport catch of pink salmon exceeds that of all other species of
salmon combined.
77
-----------,-_._--
TotallyDependlll1!PINK.;:t'"••Speculn'ionbaudonInfennuefromuletin~dataMeMginetemaSidechonne'lShSideSlough'SUeUplandSlough,Til.Tributofi..andTfibutafyMouth.,7/'<",:;f!Til!..."~~~..-..-.........,.,SU....."c •..~..0..,..~?0.'"......,...•Til!...~!.........,li':,;:~II~~'7..-~~:su..."\':..."~c!~~~~~l~~~iMI551010U,eHeOyyUseRor.OfLlttl.UseMod.oleUseIV<.>CO0...0D-E-«>>0..a::........,-CO0J(..'0CAdultMIgratianSpawningaIncubationOutmigrotingJuvenilesFigure2-17.Seasonaluseofmacro-habitatbypinksalmonabovetheChulitnaRiverconfluence(RM98.5).DatasummaryfromADF&G(1983a,1983b).
____UPPER COOK INLET HARVEST
(Includ••non-SUlilna ItOCk.)
----SUBSISTENCE-TYONEK
----EAST SIDE SPORT FISH
--------WEST SUSITNA SPORT FISH
_•••_•••-TOTAL SPORT FISH
3
2100
2400
0
LIJ
t;2100
LIJ
~
c(
%:
1800
%:
(I)-IL.-IL.
0 1500
(I)
0
Z
c(
(I)
::>IZOO0
%:
t-
900
600
300
O+-.....:;r-......-;....-~-:.---r-...;.---r--r---,r--r----,r---r-r---r-.,.----T==r=~=.:::,.:..:.a;;;c::::=r--r
1960 61 62 63 64 6:1 66 61 lIB 69 10 11 12 13 74 n\16 17 78 19 80 81 1982
YEARS
riqure 2-18.Ha rvest summary of Cook In 1et and Sus itna Ri vcr pi nk
salmon stocks.Harvest data from ADF&G (198lf)and
K.Florey (Personal communication,ADF&G.AnchoraCle),
subsistence catch data from Foster (1982)and sportfish
catch data from Mills (1982).Data from 1982 are
preliminary.
79
2.5.1.2 Adult escapement
An accurate estimate of pink salmon escapement into the Susitna River is
not available.Sonar counts at Susitna Station have provided an escape-
ment index that has been used for management purposes in recent years.
An escapement estimate for the Susitna River drainage,that exclude'S
tributary streams below river mile 77 and above river mile 6 with the
exception of the Yentna River drainage,has been calculated.The Yentna
sonar counts were combined with the Sunshine station Petersen estimates
producing a total estimate of 85,600 pink salmon in 1981 and 890,500
pink salmon in 1982 for this portion of the drainage.
Escapement estimates for each of the sampl ing sites conducted by the
Su-Hydro Studies are included in Figure 2-19.These figures use the
sonar sites at Yentna Station and the Petersen population estimates at
Sunshine,Talkeetna and Curry Stations.Total estimates of 73,000 fish
above Talkeetna in 19B?as compared with the 1981 estimate of 2,300
indicate that the even year had a higher proportion of fish using this
reach of river then the odd year when compared with the overall Susitna
River escapement.
Sonar counts were conducted at Sunshine and Talkeetna,in addition to
the estimates obtained by Petersen indices.Differences between the
estimates obtained by the Petersen indices and the sonar counts are
discussed in ADF&G (1983a)and Appendix A.
80
0+--------
YEARS
Eitlmated Total Sportflsh
Harve.'of the SUIltna River
Escapement Eltlmation by Sonar
Countl at the Ventna Station
Peter,sen Population Estimates
at Sunshine Station
Petersen Population Estimates
at Talk.etna Station
Petersen Population Eatlmates
at Cu r;y Stat Ion
PIN K
~•
[J]
till•
10
20
300
200
:I:en-100
IJ..,v
LL
0
en !so0
Z
<ten
::>
0:r::.-
30
-
-
-
-
-
-
riqure 2-19.Summary of the population estimate and sportfis~
harvest for adult pink salmon within the Susitna River.
Sportfish harvest data from Mills (1982)and escapement
and population estimates from ADF&G (1983a).
-81
2.5.1.3 Habitat and environmental parameters associated with the
adult phase of the life cycle
As with the other salmon species during the upstream migration in the
mainstem Susitna,pink salmon encounter varying environmental con-
ditions,including discharge and temperature variations.As they
approach their natal spawning areas,the adult pinks must be able to
gain access into the spawning clear water tributaries and sloughs.
Pinks spawn primarily in tributaries but limited numbers were observed
spawning in sloughs in 1982.Although not as important to the pink
salmon population as for the chum or sockeye population,the effects of
mainstem discharge on slough passage and usable spawning habitat have
some importance to the continued propagation of the species in the
Susitna River.
2.5.1.3.1 Discharge,water quality,and temperature relationships
with the adult salmon migration
The pink salmon upstream migrations exhibit a minor inverse correlation
with discharge as it appears that rapid increases in discharge and
perhaps the associ ated decrease in temperature,decrease the mi grcti on
rate.All of the adult salmon species were similarly affected.
Access requirements into the major tributaries is similar to the other
species and has been evaluated by Trihey (1983).Pink salmon were found
in virtually all of the minor tributaries in the Susitna River above the
82
Chulitna confluence (fourteen in total).Indian River,Fourth of July
Creek,Lane Creek and Portage Creek had the hi ghest ;ndex counts.
Because of the broad distribution of this species,access into the
smaller tributaries is also important.Studies of the mouth of some of
the smaller tributaries under alternative flow regimes has been
conducted by R&M Consultants (R&M 1982).
As previously noted,the clear-water feeder streams support the majority
of the pink salmon spawners with sloughs having a minor role.Passage
into the sloughs at the various stage levels has been evaluated for
those species 1isted in Appendix B and apply to pink salmon as well.
Important sloughs for pink salmon include 11,20,21,6A and 68.Slough
15,although not assessed,had large numbers of pink salmon present.
An analysis of the hydraul ic conditions of Slough 8A,9 and 21 are
presented in Appendix D.Because of the limited use of sloughs by pink
salmon,insufficient data were obtained for this species to develop
reliable criteria for projecting habitat availability under various flow
regimes.
Habitat requirements associated with spawning have not been established
for this species because their spawning habitat is generally not associ-
ated with the Susitna mainstem.However,such information will be
useful to ascertain if adverse effects of the project can be mitigated
by development of spawning populations in the I1ldinstem under post-
project conditions.The limitations of the existing data base may be
partially remedied during the upcoming field season,but the odd year
83
may limit the amount of data collected and not reflect the full spectrum
of habitat used by the stronger even year run.
The thermal differences between the sloughs and the clear water tribu-
taries may provide a partial explanation for their apparent preference
for tributary habitat.Pink salmon spawn somewhat earlier than other
species (except chinook)which accelerates initial development before
the winter cold water temperatures begin to retard development rates.
Other factors,such as substrate stability during the incubation period,
ice processes,and effective cover during spawning may limit the pink
salmon's selection of spawning habitat.The other factors discussed for
limitations on mainstem spawning for the other salmon species,apply
equally to pink salmon and are not repeated here.
2.5.2 Incubation and emergence phase of life cycle
Because most of the population of pink salmon use the clear water
tributaries for spawning and subsequent incubation,little study has
been conducted on these phases of the life cycle of this species.To
evaluate the potential of the mainstem Susitna under post-project
conditions,it is desirable to collect information on the conditions
associated with embryo development in the clear water tributaries.
Studies of thermal requirements and associated developmental rates of
pinks in clear water tributaries are planned for the fall and winter of
1983.
84
2.5.3 Juvenile rearing and migration phases
Pink salmon usually outmigrate immediately upon emergence from the
gravel in the spring and have a very abbreviated freshwater life cyc"le
(Morrow 1980).Most rear"ing probably occurs during the outmigration
through the mainstem and in the lower reaches of the Susitna and its
estuary.
2.5.3.1 Timing of outmigration from the tributaries,sloughs and
mainstem and its relationship to environmental changes
Studies conducted during the spring of 1983 should provide more insight
into the outmigration and emergence of pink salmon.Available data
suggest emergence will occur as early as late March and continue through
the end of May.The outmigrant trap,which began operation on June 18,
collected very few of this species;perhaps outmigration was essentially
complete by this time.
Only limited information is available on environmental factors that
affect pink salmon development rates during embryo development.Again,
ongoing studies should provide more information as to what factors
influence this outmigration.
2.5.3.2 Other physical and biological constraints
The freshwater juvenile life phase of pink salmon is rather brief.The
major factor affecting freshwater survival after emergence is probably
85
predation by resident fish species or birds.We have no data on the
effect of predation on survival of pink salmon juveniles in the Susitna
River.However,if a substantial reduction in turbidity of the Susitna
were to occur following flow regulation,predation may be accelerated.
During the lower flow years on the Fraser River,decreased survival of
pink salmon in the estuary was observed (Vernon 1966).Such factors may
be equally important in the Susitna River.
86
2.6 Rainbow trout
Rainbow trout are one of the more important sport fish in the Susitn&
River drainage.Although not numerous,they are the object of an
intensive fishery at areas of local concentrations.Rainbows are
normally associated with the clear water tributaries but are found
throughout the river.The tributaries of the Susitna River,such as
Portage Creek and Indian River,are near the northern-most point of the
rainbow trout's natural geographical distribution in North America.
Therefore,the species may be very sensitive to environmental changes,
particularly with regard to its reproductive cycle.
2.6.1 Adult phase of life cycle
2.6.1.1 Sport fishery harvest
Sport fishing for rainbow trout occurs throughout the open water season.
Rainbow trout fishermen in the Susitna drainage generally concentrate
their effort at the mouths of clear water tributaries.
The sport fishery fot'rainbow trout in the reach of river above
Ta 1 keetna occurs at Whi skers Creek,Lane Creek,Fourth of July Creek,
Indian River and Portage Creek.Information on the extent of the
harvest is limited to data available fronl Mills (1982)and is pr'esented
in Table 2-1 for rainbow and all other species of sport fish.
87
Table 2-1.Summary of resident sport fishery harvest in the Susitna River,
1977-1982.*
Year
Species 1977 1978 1979 1980 1981 1982
Rainbow Trout 13655 18948 23081 20060 21843 19399
Dolly Varden 5824 9148 9518 5771 5911 6214
Arctic Grayling 11883 13325 19578 20206 17110 16272
Northern Pike 132 316 382 232 125 607
Burbot 734 424 881 1073 431 975
*Sport harvest data from Mills (1982)and preliminary 1982 data.
88
2.6.1.2 Adult population indices
The population information on rainbow trout is derived from relative
abundance data collected by electrofishing and trot 1 ine catches as
recoveries of marked rainbow trout do not provide sufficient information
to estimate their abundance.However,the relative magnitude of the
population can be estimated with this data.During the 1982 season,18
of the 195 fish tagged in 1982 and 11 of 206 fish tagged in 1981 were
recovered.These data suggest the population is small and perhaps
numbers in the thousands.Systematic collection of mark and recapture
information over selected reaches of habitat during the 1983 summer,
after migratory movement has ended,should provide more precise
estimates of local populations.
2.6.1.3 Habitat and environmental parameters associated with the
adult phase of the life cycle.
The distribution patterns of rainbow trout and other resident fish are
presented in Appendix G.The habitat of the Susitna River has been
classified into several major types.These include clear water
tributaries,tributary mouths,upland sloughs,side sloughs without
major tributaries,side sloughs with major tributaries,and mainstem
sites.In addition,the study sites examined most intensively were
further sub-divided into zones.The zone classification grouped the
collected data into areas influenced by backwater of the mainstem
Susitna,areas that had different water sources,and areas that
89
had different water velocities,
Appendix F.
This analysis is included in
The distribution of rainbow trout followed the expected pattern with
tributaries having the highest concentrations and mainstem sites having
the lowest.Sloughs were intermediate.The distribution of fish,as
indicated by catch per unit effort data,demonstrated a preference for
tributary water;the highest concentrations were found in the clear
water areas,followed by mixing zones,and the lowest concentrations
were in mainstem Susitna water during the open water season.
Comparisons of rainbow trout distributions in zones with different
velocities,i.e.zones backed up by the mainstem,and zones not
influenced by the mainstem,only showed minor differences.This
observation agrees with the general distribution of rainbow trout catch
data,and reconfirms the close association of this species with clear
water tributaries.
During the winter months,rainbow trout apparently move into the
mainstem Susitna,as demonstrated by increasing catch rates near the
mouths of the clear water tributaries.Radio-tagged fish demonstrate
little movement in the mainstem although some downstream migration has
occurred during the winter period.The fish appear to concentrate,
since catch rates of rainbow at relocation sites of the radio-tagged
fi sh appear to be hi gher.Further studi es of radio-tagged fi sh are
currently in progress and should provide better information on the
habitat utilized by this species during the critical overwintering
period.Our limited data indicate a possible association with ground
90
water areas which have warmer temperatures and higher levels of
conductivity.
2.6.2 Reproductive phase of life cycle and juvenile dis-
tribution and abundance
Because of the lack of information on rainbow trout spawning areas in
the Susitna drainage,much of this information is inferred from the
distribution of juveniles.During the spring,gravid adults have been
captured at the mouths of clear water tributaries,such as Fourth of
July Creek and Indian River.It is believed that rainbow trout in the
Susitna River drainage spawn in the upper reaches of clear water
tributaries,although limited investigations in these areas have not
documented this event.The numbers of juveniles collected are very few
when compared to other clear water spawning species such as Arctic
grayling.This suggests that spawning success is low or that the
rearing of the juvenile rainbow trout is confined to the tributaries,
and not,to any appreciable extent,associated with the mainstem
Susitna.Spawning may be a critical factor limiting the northern
distribution of this species.
Further investigations of the spawning rainbow trout and of the cleaf
water tributaries are planned during the spring of 1983 and should help
resolve this question.
91
?.7 Burbot
Burbot are corrmon in the mainstem Susitna River and are among the few
species that indicate preference for the turbid glacial water.This
species is considered a sport fish but the harvest rate is low when
compared to its relative abundance in the system.Its apparent prefer-
ence for glacial water and the possible decreases in turbidity of the
upper Susitna River under post-project development has necessitated
research on this species.
2.7.1 Adult phase of life cycle
2.7.1.1 Sport fishery harvest
Burbot harvests in the Susitna have been relatively small when compared
with other,more popular,species such as Arctic grayling and rainbow
trout.A summary of burbot sport fishing harvests is listed in Table
2-1 (Mills 1982).Burbot are primarily harvested by local residents and
its flavorful flesh is considered to be of high table quality.The
apparent abundance of this species in the river suggests that the
current populations could support a higher harvest rate.
2.7.1.2 Adult population indices
Only relative abundance information is available for burbot.Recovery
of marked fish during 1982 were limited to three of 265 tagged fish.
92
Because of their broad distribution,burbot were often caught at
mainstem sites.Populations of specific reaches of river have not been
obtained,but an intensive mark/recapture program is being initiated in
the summer of 1983 to establish reach specific densities.Further
discussion of the relative abundance data with respect to macro-habitat
differences follows.
2.7.1.3 Habitat and environmental parameters associated with the
adult phase of the life cycle
The relative catch per unit effort at the various sampling sites was
compared with the macro-habitat conditions at the sites listed in
Appendix G.In addition to the habitat conditions within different
zones,a further subdivision of the macro-habitat were evaluated for
differential catch rates (Appendix F).
As discussed earlier.burbot are primarily associated with the mainstem
river and although significant numbers of burbot were taken at tributary
mouths by electrofishing methods,this gear type is not as effective in
the mainstem habitat and a complete distribution scenario for burbot in
the Susitna River is not possible.The distribution by zones suggests a
dramatic segregation by habitat with a strong avoidance of clear water.
The distribution demonstrates preference for fast water as well as the
turbid conditions.On the Tanana River,Mecum (1982)observed a similar
avoidance of clear water sloughs and preference for the turbid side
channels.
93
2.7.2 Reproduction phase of the life cycle and juvenile
distribution
Habitat conditions associated with burbot spawning have not been
established because of difficult winter sampling conditions in the
mainstem Susitna.Studies currently under way using radio-telemetry
equipment may provide some insight into spawning requirements.Burbot
are known to spawn in the winter at the mouths of the larger lower
tributaries,such as the Deshka River.This river mouth has relatively
deep water and a silt or sand-laden bottom.
Burbot larvae were observed in the Susitna River at several sites above
Talkeetna indicating some spawning takes place in this reach.The
larvae,collected in June 1982,were associated with the silty,
low-velocity areas near the mouths of several sloughs.This suggests
that the mainstem Susitna in th-is region has limited use by spawning
burbot.Ongoing studies on the river may provide more insight into the
use of the mainstem river and further details on the timing and use of
particular habitat conditions by this species.
Intermediate age class fish were collected by the outmigrant trap
located 4.5 miles above the Chulitna River confluence.This suggests
that rearing burbot as well as the adults use the mainstem.Other than
their association with the mainstem,little is known about the specific
habitat utilized by the younger age class burbot.
94
2.8 The Whitefish -Round,Humpback,and the anadromous
Bering cisco
Two species of whitefi sh (Family Coregoni dae)are broadly di str'j buted in
the Susitna River.The anadromous Bering cisco was found to be present
in the Susitna River for the first time during the 1981 studies.
2.8.1 Adult phase of life cycle
2.8.1.1 Sportfishing and other harvests
Although whitefish species are abundant and broadly distributed in the
Susitna River drainage,statistics collected by the ADF&G Sport Foish
Division indicate that there ;s little use of these species by sport
fishermen.They are,however,utilized by sport and subsistence
fishermen in other parts of the State.
2.8.1.2 Adult populations indices
2.8.1.2.1 Round whitefish
Round whitefish were the most abundant of the whitefish species
collected in the Susitna River during 1981 and 1982.Catch per unit
effort data suggested this species is eight to ten times more abundant
than the humpback species.This species is possibly the most abundant
resident species occurring in the mainstem Susitna.
95
2.8.1.2.2 Humpback whitefish complex
Humpback whitefish were collected throughout the study areas but in
lesser concentrations than the round whitefish.Although taxonomically
complex,the species of humpback whitefish in the Susitna River has been
tentatively identified as Coregonus pidschian based on the number of
gill rakers observed in a significant sub-sample of specimens.Concen-
trations of this species occurred near Sunshine Creek and near Portage
Creek.Significant numbers were also captured,in September by the
fishwheels at Sunshine Station.This indicates a fall upstream spawning
migration.
2.8.1.2.3 Bering cisco
Prior to the discovery and identification of Bering cisco in the Susitna
River during the 1981 studies,only one confirmation of Bering cisco in
Cook Inlet was on record (Morrow 1980).The spawning areas and
associated habitat in the Susitna River have now been described.
Although a population estimate of this species was not attempted,over
500 individuals were observed or caught at the spawning areas sampled.
96
2.8.1.3 Habitat and environmental parameters associated
with the adult phases of the life cycle.
The habitat parameters associated with the whitefish species is poorly
understood.Because of the lack of economic importance of these
species,little research has been conducted on their habitat relation-
ships in northern areas.Even basic life history information is quite
limited.For example,the 1982 recapture of a Bering cisco that had
been tagged while spawning in 1981,is the only known evidence that this
species may be capable of repeated spawning.
Point specific data were recorded for a limited number of spawning sites
for these species and are listed in the data reports for 1981 and 1982.
The data is most complete for Bering cisco,which were concentrated at
the few spawning sites located.
With the exception of burbot and longnose suckers,the whitefish ap-
peared to be more capable of using the mainstem Susitna for rearing
habitat.The data suggests that round whitefish migrate into the larger
clear water tributaries in the early spring while significant numbers
remain in the mainstem Susitna.These mainstem areas are often
associated with tributary mouths or clear water sloughs where turbid and
clear water mixing occurs.
97
The humpback whitefish has similar behavior but may also have some of
their life cycle associated with the estuary.The small numbers of
humpback whitefi sh catches have precl uded obta i ni ng suffi ci ent i nfor-
mation on their habitat requirements.
2.8.2 Reproductive phase of life cycle
The majority of the data on spawning habitat conditions has been col-
lected on Bering cisco in the mainstem river.There is also some
evidence of round whitefish spawning in the mainstem.Humpback
whitefish apparently spawn in the clear water tributaries exclusively,
as we did not collect spawned out individuals associated with the
mainstem.Most of the upstream migration of humpback whitefish was
apparently associated with the Chul itna or Talkeetna drai nages,wi th
some spawning in the mainstem or tributaries of the Susitna above the
Chulitna confluence.
The hydraulic characteristics for spawning areas used by Bering cisco in
1981 and 1982 near the Parks Highway Bridge,have been described.These
data are presented in the basic data reports.Because this species
spawns during early October,changes in discharge of the mainstem during
freeze-up and during the incubation period could subsequently affect
reproduction.Changes in discharge could dewater the incubating eggs
while higher velocities could scour the spawning areas.The relatively
stable discharges under natural conditions during this period may be
indicative of a requirement for successful reproduction of this species.
98
Sufficient spawning location data to evaluate hydraulic conditions and
requirements for the other whitefish species has not been collected.
2.8.3 Juvenile rearing and migration
Substantial numbers of juvenile round whitefish were collected at
mainstem sites or adjacent to the clear water sloughs of the Susitna.
Throughout the summer of 1982,juveniles of this species were collected
by the outmigrant inclined plane trap located 4.5 miles above the
Chulitna River confluence.
In August of 1982,substantial numbers of humpback whitefish were also
collected in the trap.This species may be anadromous and these catches
could be indicative of a juvenile outmigration to the Cook Inlet
estuary.Although evidence of juvenile outmigration exists for the
other whitefish species,we do not have evidence of riverine rearing or
juvenile outmigration for Bering cisco.Instead,it is believed that
the young of this species outmigrate as larvae and rear in the Cook
Inlet estuary.
The habitat requirements for juveniles of all three species are poorly
understood.Although significant numbers have been collected at
mainstem sites,they appear to concentrate near the sloughs and
tributary mouths.
99
2.9 Eulachon
Eulachon are probably the most abundant species of fish that occur "in
the Susitna River drainage.They currently are not significantly
exploited but may be very important in the estuarine and pelagic
environments as a food item for other species of fish and sea mammals
(other investigations are cited by Hart 1973).
2.9.1 Freshwater reproductive phase of life cycle
The Susitna Ri ver has two runs of eul achon.In 1982,the fi rst run
began in mid May and the second run began on June 1st.The runs
progressed rapidly and were essentially over by June 8th.The runs
extended upstream in the mainstem Susitna to river mile 48.5 with most
of the spawning occurring between river mile 8.5 and the Yentna River
confl uence.
2.9.1.1 Sport fishery harvest
Eulachon are not heavily exploited.Observations of the sport fishery
during the spring of 1982 "indicated that the primary effort occurs
between river miles 10 and 30.Field personnel estimated that several
thousand eulachon were harvested during this period.There currently is
no commercial harvest.
100
2.9.1.2 Adult escapement
The populations of eulachon are very large in the Susitna River and are
believed to be composed of millions of fish.Large accumulations of
carcasses several feet deep were observed to extend over hundreds of
feet,after spawning was completed.Although this species is capable of
repeated spawning,mortality rates after the 1981 and 1982 runs observed
by ADF&G biologists were apparently very high.Much of the information
presented in the (ADF&G 1983a)data report is the fi rst inforrnati on
recorded on the distribution,abundance,and habitat used by this
species in the Susitna River.
2.9.1.3 Habitat and environmental parameters associated with
spawning
The runs entered the Susitna River apparently without any obvious
correlation with water temperature or tidal stage.The species appears
to utilize only the mainstem Susitna and the Yentna River before
spawning.This species apparently uses a broad range of habitat
conditi ons with the moderate velocity areas bei ng preferred.Spawn;ng
takes place in water depths of a few inches to greater than four feet.
Substrate varies considerahly,but areas of sand and gravel or silt and
gravel sites are preferred.
The data base for evaluation of habitat requirements for eulachon is
small since this was the first year this species was studied.Further
information will be collected during the 1983 spring investigations.
101
2.9.2 Juvenile emergence,rearing and migration
The juvenile portion of the life cycle and outmigration has not been
studied and all information on this subject must be inferred from the
timing information obtained on the adult spawning run.
Eulachon eggs hatch in 20 to 40 days (Hart 1973),depending upon the
water temperature.Shortly after hatchi ng the young pass ive ly mi grate
as larvae to the Cook Inlet estuary where they rear.The rearing phase
of the life cycle is entirely in the estuarine environment (Morrow 1980)
rhiCh indicates the larvae would be out of Susitna River by mid-July of
each year.
102
2.10 Miscellaneous game species (Arctic grayling and Dolly Varden)
Arctic grayling and Dolly Varden are two common species in the Susitna
drainage which are the target of a sport fishery at clear water
tributary mouths.Grayling are common above the Chulitna confluence and
are frequently caught by sport fishermen.Dolly Varden are common in
the Tal keetna River and the Susitna River downstream of the Tal keetna
River confluence.
2.10.1 Adult phase of the life cycle
2.10.1.1 Sport fisheries harvest
Harvest data for grayling and Dolly Varden have been compiled by r~ills
(1980)using data from the statewide angler surveys (Table 2-1).Obser-
vations of harvest above the Chulitna confluence indicate grayling are
the most commonly caught resident sport fish in this area and rainbow
trout are also frequently caught.The sport fisheries are primarily
restricted to Indian River.Portage Creek,Lane Creek,Fourth of July
Creek and Whiskers Creek,although some harvest occurs at other small
tributaries.Dolly Varden are rarely caught in this area as reflected
in the relative abundance data presented in the data reports.In the
Susitna below the Chulitna confluence,sport fisheries occur at most of
the clear water tributaries for both species.Dolly Varden are much
more common in this lower area.
103
2.10.1.2 Adult population indices
The relative abundance of grayling and Dolly Varden have been described
in the data reports for 1981 and 1982.Electrofishing in the mainstem
and clear water tributary mouths in both reaches indicated migratory
movements of both species during the spring.Grayling were also abun-
dant in the fall.Limited sampling in the lower river in the fall of
1982 was probably the reason a similar trend was not observed for Dolly
Varden.This data infers that the mainstem Susitna is used by these
species from September until the second week in June.
2.10.1.3 Habitat and envi ronmenta 1 parameters associated wi th
the adult phase of the life cycle.
The distribution of grayling in macrohabitat areas associated with the
mainstem Susitna is reported in Appendix G.Adult grayl ing were most
often associated with the mouths of the clear water tributaries.These
areas were essentially,extensions of the tributary during the summer
months.The mainstem Susitna was much more important to the younger age
classes in the open water season.Since few Dolly Varden were collected
above the Chulitna confluence,very little quantitative data was
obtained for this species on this reach.They appear however,to follow
a pattern similar to the distribution of grayling with migratory
movements up the clear water tributaries in the spring and back down in
the fall.As this species is known to be a predator on salmon juveniles
and salmon eggs,their distribution may be more closely associated with
the salmon distribution than the specific environmental conditions.A
104
stunted form of this species resides in the upper areas of the Indian
River,Portage Creek and tributaries of the Susitna above Devil Canyon.
We have very little data for this stunted form of the species but they
appear to be broadly distributed but not abundant.Their habitat
requirements are not known.Details of their observed distribution are
discussed in the impoundment area data reports.
2.10.2 Reproductive phase of the life cycle
Habitat conditi ons associ ated with the spawni ng of these speci es have
not been established because spawning occurs in the clear water tribu-
taries.Apparently mainstem conditions and the habitat in the sloughs
is inadequate for their successful reproduction.The presence of
juveniles of both species in the reach of river above the Chulitna
confluence suggests successful reproduction does occur in the clear
water tributaries in this portion of the Susitna basin.
2.10.3 Juvenile rearing and migration
Juvenile grayling were frequently collected at the mouths of clear water
tributaries in addition to mainstem areas which suggests that during the
summer months suggest the mainstem is used by this species for rearing
of juveniles.The larger fish may occupy the better rearing habitat in
the clear water tributaries while the younger age class fish are dis-
placed into the mainstem Susitna.The distribution of juveniles in the
mainstem areas were generally at areas of lower velocity.
105
I uvenile Dolly Varden were collected in insufficient numbers to suggest
any trends or hypothesis as to habitat relationships.
106
2.11 Other species of the Susitna River drainage
The Su-Hydro Aquati c Studi es have concentrated on speci es with
significant commercial or sport fishery harvests and on other species
that have important biological considerations.The following species to
be discussed often are abundant but existing information indicates they
have broad environmental tolerances or are rare in the Susitna River
habitats that may be affected by the development of the hydroelectric
project.These populations could become more important if conditions
were to develop under post-project operation that benefit these species
to the detriment of the species that are of more economic importance.
We currently lack enough information on these species to predict
responses by their populations to altered environmental conditions.
2.11.1 Threespine stickleback
Threespine stickleback are most common in the Susitna River below the
Chulitna River confluence.Large numbers upstream of the confluence
were collected in the vicinity of Whiskers Creek and associated slough
in 1981;the 1982 catch data for this reach was much less.The reason
for this difference is not known,however the high water during 1981 may
be related to the decreases in population.As threespine stickleback
may be competitive with rainbow trout or sockeye salmon juveniles,
increases in numbers may not be desirable.If the above hypothesis is
true for the Susitna River habitats,stabilization of flows could cause
substantial increases in numbers,particularly above the Chulitna
107
confluence.Migratory movements during the spawning period for this
species suggests they are able to redistribute quite easily.The
outmigrant trap catch rates for threespine stickleback in August and
September indicated that large number migrate into the lower river upon
the onset of winter.Observations in May.1983 of very large upstreanl
migrations of threespine stickleback in the lower Susitna River suggest
that the anadromous variety of this species occurs in the Susitna River
drainage.
Factors which affect the abundance of this species are poorly under-
stood.Monitoring of the threespine stickleback population with corre-
sponding measurements of mainstem discharge and associated habitats
appears to provide the best method for estimating their longterm
responses to discharge variations in the Susitna mainstem.
2.11.2 Longnose suckers
This species is broadly distributed in the mainstem Susitna and utilizes
turbid water environments.They are also associated with clear water
tributaries as are almost all of the species that occur in the system.
Because of their relative abundance.we have collected data associated
with their rearing habitat for both adults and juveniles.The spawning
areas that have been characterized were associated with the mainstem
Susitna.Longnose suckers are broadly distributed and are found in the
mainstem Susitna above Devil Canyon.Juveniles have been collected in
large numbers in the clear water sloughs above the Chulitna confluence.
One unusual finding was the presence of male longnose suckers in spawn-
108
ing condition in the fall.This species is generally considered to be a
spring spawner and the presence of ripe males in the fall was unexpected
(Morrow 1980).Spawning was not observed and whether ripe males
overwinter in this condition or a fall spawning population exists is not
known.
2.11.3 Arctic lamprey
-
Arctic lamprey were not collected in large numbers;however,because the
collection methods used were not effective for this species.The
species is broadly distributed in the Susitna River with the larqest
numbers observed below the Chulitna confluence.There appears to be an
anadromous form as well as a resident form of this species in the river.
Size is used as the primary criterion in distinguishing these foy'ms
(Morrow 1980).We did not obtain any evidence of Arctic lamprey being
parasitic on other freshwater species collected.Spawning is thought to
occur in the clear water tributaries above the Chul itna confluence as
concentrations of ammocoetes were collected at Gash Creek and Whiskers
Creek.Spawni ng was observed and habitat condi ti ons recorded in Bi rch
Creek Slough.Other than the distribution associated with collection of
adults and immature fish,little information has been obtained on the
habitat relationships of Arctic lamprey.Morrow (l980)concludes that
there is little information indicating that this species has significant
importance to man.
109
2.11.4 Slimy Sculpin
The slimy sculpin is broadly distributed in the Susitna River basin.
This species is common in the clear water tributaries and often appears
to be abundant.Lesser numbers are also found in turbid water mainstem
environments.This species is almost entirely insectivorous but its
feeding habits confine it to bottom organisms and it probably does not
compete with salmonids.Morrow (1980)suggests that when large numbers
occur they could compete with salmonids although this has never been
documented.
We have observed what appears to be a displacement of salmonids in micro
habitat areas of the sloughs and clear water tributaries.Riffle areas
of moderate velocity that had high numbers of sculpins,usually had few
or no chinook juveniles.Peripheral areas with more depth and cover had
high concentrations of juvenile chinook.Wangaard (personal communi-
cation)observed in the Kenai river,what appeared to be territorial
defense by slimy sculpin toward juvenile chinook when they would
approach the substrate over which sculpin were feeding.Other than the
general distribution of this species in the macro-habitat areas sampled,
we have not clearly defined habitat relationships.Their broad dis-
tribution suggests that they would not be particularly sensitive to
changes in their environment but that local populations might be
affected.
110
2.11.5 Other species
Northern pike is the only other species collected during the course of
the Su-Hydro investigations.One northern pike was collected in the
lower river in Kroto slough in 1981 and one was captured at the Yentna
fishwheel site in 1982.This species has recently become established in
the Yentna drainage.The distribution of northern pike may be expanding
which is not considered desirable because of the predation potential on
\
salmonids.This was the first record of this species in the mainstem
Susitna.
There are probably several other species,not collected by this program.
which are present in the river near the estuary.These include the
Pacific lamprey,nine-spined stickleback,other species of sculpin,
starry flounder,and other species of smelt (Morrow 1980).
111
3.THE FISHERIES STUDIES WITHIN THE BOUNDARIES OF THE PROPOSED
IMPOUNDMENT ABOVE DEVIL CANYON
Studies conducted during 1981 and 1982 above Devil Canyon have been
directed at estimating the populations of resident species in the clear
water tributaries within this region and of certain portions of the
mainstem Susitna within the impoundment zones.This information has
been used to estimate the exploitation rate that these streams are
capable of sustaining by sport fisheries.
3.1 The fishery resources of the clear water tributaries of the
impoundment zones
The fisheries studies over the 1981 and 1982 period have concentrated on
the Arctic grayling population associated with the clear water tribu-
taries of the impoundment.These streams are essentially unexploited
and offer high quality sport fishing.
The studies included surveys for salmon that have ascended Devil Canyon.
Salmon have been documented above the first rapid in Devil Canyon but
none have been observed above the rapids below Devil Creek,the
uppermost rapids in Devil Canyon.
Other studies included investigations of mainstem habitats and fish
populations in Sally Lake.This small lake lies in the Watana Creek
drainage and will be inundated by the Watana impoundment.
112
3.1.1 Population estimates or indices of species present
within the clear water tributaries.
Grayling population estimates for reaches of clear water tributaries
within the impoundment zone are summarized on Table 3-1.Insufficient
data were obtained on the other resident species for population esti-
mates.Estimates of densities of fish have not been obtained for thE'
mainstem Susitna,although the mouths of the clear water tributaries
were included in the estimate on Table 3-1.
The grayling populations were calculated for the month of July only
based on the August recaptures.Grayl ing are relatively non-migratory
at this time so the estimates provided are indicative of the population
densities that occur within specific reaches during the summer.
3.1.2 Population dynamics and harvest effects on
grayling in the tributaries
-
The primary collection technique used for sampling Arctic grayling was
hook and line.The high velocity and low conductivity of waters in this
area precluded sampling by electrofishing.The catch rates ard
selectivity of the gear provided the opportunity to analyze the
potential effects of incrementally increasing sport fishing on the
Arctic grayling populations.This analysis is presented in Appendix I.
The Arctic grayl ing P?pulation,under the assumptions of this model,
demonstrated a susceptibility to fishing pressure with the larger fish
113
Table 3-1.Arctic grayling population estimates by trigutary habitat evaluation
location,Proposed Impoundment Areas,1982.
Population a
Location Estimate----
Oshetna River 2426
Goose Creek 949
Jay Creek 1592
Kosina Creek 5544
Watana Creek 3925
Deadman Creek c 734
Tsusena Creek d 1000
d 176FogCreek
Totals 16,346
Grayl i ng/Grayling/
Mile Acre
1103 56
791 90
455 101
1232 69
324 44
1835 273
440
664
acorrection factor included.
cIncludes only that part of Deadman Creek below falls.
d1981 estimates.
e From ADF&G (1983d).
114
quickly disappearing from the population under relatively low levels of
fishing pressure.The maximum sustained yield,°in terms of numbers of
fish caught and kept,is approximately four times the level of effort
expended by ADF&G crews during July of 1982.This model also
demonstrates that the initial years of harvest will provide a relatively
high level of catch before the population becomes stabil ized at the
maximum sustained yield harvest level.The catch per unit effort of the
sport fishermen can be expected to decl ine accordingly following the
initial years of harvest.
The onset of construction and the influx of 3,000 or more construction
workers and the opening of the area to the public by the construction of
access roads,will result in substantial increases in fishing pressure
on these streams.Depending on regulations and access control,this
model can be used to evaluate the probable effects of the fishing
pressure change on the grayl ing populations in the system and car
suggest some type of mitigation strategy .
.....
3.1.3 Relationships of growth,population,and production
data to general and site specific habitat variables.
-
The Arctic grayling growth rates in the impoundment do not vary
appreciably between tributaries although the rate of growth of Arctic
grayling varies among individuals.Statewide,the mean rates appear to
decrease as one goes north in latitude (Armstrong 1982).This suggests
that the length of the open water season probably affects growth rates
more than other variables.A more complete description of growth of
115
Arctic grayling is presented in Appendix J.The Arctic grayling in the
impoundment also have significant migrations between tributaries,
suggesting that the populations are not distinctly separate and can be
pooled for analysi~.
An examination of the habitat variables and variations among the tribu-
taries examined is presented in Appendix K.These factors are most
likely affecting the densities observed rather than the growth rates of
the fish.The territorial behavior of this species probably influences
the numbers of fish that can occupy suitable habitat and the
availability of this habitat determines the densities of fish in the
system.
3.2 The fishery resources of the mainstem Susitna within the
impoundment zones.
The mainstem river primarily serves as a migratory corridor for Arctic
grayling but supports populations of burbot,round and humpback
whitefish,longnose suckers,and cottids.This habitat also is
apparently the overwintet'ing area for the impoundment tributary popu-
lations.
Juvenile Arctic grayling were found in sloughs of the mainstem Susitna
but quantitative information as to significance of these findings were
not obtained.The trend of juveniles and younger age class fish being
associated with the mainstem in the lower river below Devil Canyon may
well be true in the impoundment.
116
The mainstem population structure of burbot in the impoundment appears
to resemble that of the lower river.No quantitative information on the
density of the species in the mainstem is currently available.
The overwintering study is currently in progress and will be descr"ibed
in a separate report.Only limited data have been obtained although it
appears that all fish monitored by radio-telementry migrated into the
mainstem Susitna to overwinter.
3.3 The fishery resources of the lakes within the impoundment
zone.
Sally lake lies on a bench above Watana Creek and is entirely within the
impoundment zone.Our studies have indicated a population of Arctic
grayling and lake trout in this lake.The Arctic grayling are the most
abundant although insufficient data were obtained to estimate the
populations.The number of Arctic grayling and lake trout in Sally Lake
are probably small.varying from a few thousand to several hundred
respectively.
Several other small lakes are also found in the impoundment zone.These
lakes have not yet been studied.Investigation of these lakes are
planned in the upcoming summer.
117
4.SUMMARY OF THE INSTREAM FLOW RELATIONSHIPS OF THE FISHERIES
RESOURCES DOWNSTREAM OF DEVIL CANYON
4.1 Introduction
The studies of the major habitat types of the Susitna River below Devil
Canyon are summarized in this section of the report.The habitat
characteristics which are presented in this summarization are only those
which are likely to be influenced by mainstem conditions (namely
di scharge,water temperatu re,and turbi dity)and 1 ike ly to impact upon
fish populations.
The studies downstream of Devil Canyon to the Chulitna confluence
(t'eferred to here as upper river)and the findings below the Chulitna
confluence (referred to here as lower river)are discussed separately.
These reaches differ in physical and biological characteristics,and in
the anticipated impacts of the proposed hydroelectric development.Our
level of understanding is much more refined above the confluence than
below due to the greater level of information available.
4.2 Key findings of fisheries studies downstream of Devil Canyon
to the Chulitna confluence
4.2.1 Principal instream habitat types
The principal instream habitat types occurring in this reach of the
Susitna River drainage are the mainstem,side channel,side slough,
upland slough,tributary,and tributary mouth habitats.Volume 4 of
118
the Basic Data Report describes and defines these general habitat
categories (ADF&G 1983c).
4.2.2 Primary species composition and seasonal availability of
instream habitat types
4.2.2.1 Mainstem and side channel habitats
The mainstern and side channel habitats of this section of the Susitna
River function as a migrational corridor;as rearing/feeding habitat;as
overwi nteri ng habitat;and as spawni ng/i ncubation habi tat for many (,f
the resident and anadromous species.The principal fisheries resources
are most dependent on this area for migration and overwintering.
Spawning migrations by the five Pacific salmon species are a well
establ ished use of this habitat type.Spawning migrations of adult
anadromous Arctic lamprey also occur.
Other fish species which probably use the rnainstern and side channels for
spawning migrations include rainbow trout,burbot,Arctic grayling,
round whitefish,threespine stickleback,and longnose sucker.
-
Outmigration of juvenile salmon primarily occurs during and just
following breakup (late March-early June)for pink and chum salmon and
throughout the open water season for the other species.
119
----------_._-_._-----------,-.-.--.--_._----_....
The use of mainstem and side channels as a migrational corridor for
rearing and overwintering redistribution is another important charac-
teristic of this habitat.Juvenile chinook,coho,and sockeye salmon,
burbot,Arctic grayling,and rainbow trout probably use the rnainstem and
side channels for both overwintering and rearing redistribution.
The mainstem and side channel habitats are heavily used by burbot,round
whitefish,and longnose sucker for rearing and feeding habitat.
Overwintering habitat use of the mainstem and side channels in this
reach of river is probably important to juvenile chinook,coho,and
sockeye salmon,rainbow trout,and other species as well.However,
evidence supporting this use by these species is mostly circumstantial
because of limited winter data.
The mainstem and side channel habitat types are used as
spawning/incubation habitat by adult chum salmon but is pr'obably of
limited importance to the species.Coho salmon were observed spawning
in this habitat type in 1981 but not in 1982.This use is also of
probable importance,although unsubstantiated,to longnose sucker,
burbot,and round whitefish.
4.2.2.2 Side slough habitats
The side slough habitats of the Devil Canyon to Chulitna reach of the
river are important for spawning/incubation of chum and sockeye salmon.
120
-
Coho and pink salmon also utilize this habitat for spawning/incubation,
but it is apparently not as of great importance.
The side slough habitats in this reach of river also function as impor-
tant rearing and feeding areas for juvenile chinook,coho,and sockeye
salmon during the open water season.Since juvenile sockeye catches
have not generally been large,data supporting the importance of this
habitat for rearing of sockeye is not as convincing as is the case for
juvenile chinook and coho.Juvenile chum may also use this habitat for
a short rearing period prior to outmigration.Rainbow trout,burbot,
round whitefish,and Arctic grayling also utilize this habitat type for
rearing/feeding.
The side slough habitat type in this reach of river is also used as
overwintering habitat by juvenile chinook,coho,and sockeye salmon.As
was the case for the mainstem and side channel habitats,winter sampling
conditions have limited data collection.However,in the case of side
sloughs with upwelling water sources,it is highly likely that
significant overwintering does occur.
4.2.2.3 Upland slough habitats
The upland sloughs habitats of the Devil Canyon to Chul itna t'each of
river are apparently most important as rearing/feeding areas for
juvenile chinook,coho,sockeye,and possibly chum salmon during the
open water season.Observations are limited in the cases of sockeye a~d
121
chum.Rainbow trout,round whitefish,and Arctic grayling also utilize
the upland sloughs for rearing/feeding purposes.
The upl and sloughs also function as spawning/i ncubation habitat for
small numbers of coho,sockeye,chum,and pink salmon.This use of this
habitat is probably not of great importance to these species in terms of
overall spawning habitat availability.
In upland sloughs with upwelling or tributary water sources,juvenile
chinook,coho,and sockeye salmon overwinter.Again,data
substantiating winter uses of habitat are minimal.
4.2.2.4 Tributary and tributary mouth habitats
The distl'ibution and abundance studies of the fisheries resources in the
tributaries focused on their confluence with the mainstem river,side
channels and slough habitats.Accordingly,most of the observations on
the seasonal utilization and species composition are associated with the
tributary mouth,with only inferences possible for the tributa~y
habitat.Some data are available on spawning by adult salmon species.
Use of tributary and tributary mouth habitats for spawning/incubation is
important and well substantiated for chinook,coho,chum,and sockeye
salmon.This habitat is the primary spawning habitat for chinook and
pink in this reach of river.Rainbow trout,humpback whitefish,Arctic
grayling,and Arctic lamprey also utilize this habitat for
spawning/incubation.
122
-
.....
-
Rearing/feeding utilization of this habitat by juvenile chinook,coho,
and possibly chum salmon,rainbow trout,burbot,round whitefish,Arctic
grayling,and longnose sucker is probably of importance.
4.2.3 Influence of mainstem discharge and water quality on
instream habitat types
4.2.3.1 Mainstem and side channel habitats
The influence of mainstem discharge and water qual ity conditions in the
ma-instem habitats is obviously a case of complete dependency.The
i nfl uence upon side channel habitats is nearly as dependent.As flow
levels drop,the heads of the side channel are cut off from mainstem
flow.At such low flows the side channels resemble side sloughs in that
they are cut off from the mainstem at the upstream end and have
backwater zones at the downstream end.At most "normal"open wah~r
season flow levels,the side channels convey mainstem flow.
The i nfl uence of rna i nstem di scharge upon the use of the rna i nstem and
side channel habitat types as migrational corridors (for spawning
migrations,redistribution,and outmigration)is basically a question of
mediation.Mainstem conditions probably affect the day to day timing
and degree of these migrations rather than being an "all or none"
relationship .
123
Mainstem discharge is positively correlated with juvenile salmon daily
outmigration rates in the mainstem and side channel habitats although
the correlation is small (Appendix H).
The influence of mainstem conditions upon redistribution of fish for
rearing/feeding and overwintering,and upon spawning migrations,is
currently not well defined.Intuitively,mainstem flow and temperature
1eve 1s affect the seasonal timi ng and success of such mi grations,but
data are lacking to make definitive conclusions.
The use of the mainstem and side channel habitats for rearing/feeding is
most likely affected by mainstem discharge t temperature,and turbidity
effects.Certain fish species exhibit obvious strong correlations with
turbid water.For example,burbot are generally found in turbid water
while juvenile coho occur in clearer water (see Appendices F and G).
AccordinglYt factors which affect the turbidity levels in these habitats
would most likely affect the distribution and abundance of such species.
Overwintering success of fish in the mainstem and side channel habitats
is probably most closely related to ice formation processes and the
distribution and degree of upwell ing areas.These habitats are most
likely the major sites for overwintering in the area between Devil
Canyon and the Chulitna confluence.
The use of the mainstem and side channel habitats in this reach of river
for spawning/incubation is not prevalent.The mainstem flow and
temperature may affect redd selection.Depth and velocity conditions,
124
",~."
-
-
present during spawning,and intragravel conditions,present during
incubatiori,are affected by mainstem discharge and temperature.A
quantification of the available habitat at any given discharge at
mainstem and side channel habitats is not yet available.
4.2.3.2 Side slough habitats
Above certain discharge levels,generally between 20,000 and 25,000 cfs,
the side sloughs of the river between Chulitna and Devil Canyon directl,Y
connect to the mainstem or side channel flow.At these flows,the side
sloughs convey turbid mainstem discharge.At lower flow levels,the
mainstem stage creates backwater areas at the mouths of the sloughs.
The periodic breaching of slough heads by mainstem flows is an important
factor in determining side slough morphology,substrate composition,and
terrestrial vegetation encroachment.
Because of the importance of the side slough habitats to salmon in this
reach of river,a large amount of the sampling efforts of the various
studies have focused upon this habitat type.The critical levels of
flow for head breaching and access through the slough mouths for select
slough habitats have been evaluated.The influence of mainstem
conditions upon the side slough habitats for spawning has been evaluated
for a limited range of side slough discharges because basin wide low
flow conditions in August,1982,precluded observation of spawning at
flow levels which would have been considered "normal"(Appendix D).
125
The relationship between mainstem conditions and the rearing/feeding of
fish in the side sloug~habitats has been evaluated.The dynamic nature
of the side sloughs,in terms of the opening and closing of the slough
heads and the extent of ma;nstem backwater effects,suggest a system
which is highly dependent on mainstem discharge change from day to day
and season to season.As was the case for side channels,mainstem
effects upon side slough turbidity levels would be expected to impact
species which exhibit avoidance of turbid water (or exhibit preference
for turbid water).The relationship of selected juvenile salmon and
resident fish of different species to the hydraulic zones associated
with these side sloughs is presented in detail in Appendix F.These
data i ndi ca te that speci es respond di fferently,with the habitat index
for rearing sockeye and chum decreasing with decreasing discharge,the
habitat index for juvenile chinook changing minimally,and the habitat
index for rearing coho responding positively to flow decreases.
Individual sloughs vary considerably from each other with morphological
differences being a dominant factor in this variability.
Mainstem influence upon the side slough habitats for use by overwinter-
ing fish and incubating salmon embryos is not presently well defined.
Such influences are most likely related to indirect impacts such as
influences on rates of upwelling water sources and winter overflow of
the slough heads caused by ice processes.These effects could increase
mortality by dewaterjng habitat or by creating sudden changes in
temperature.
126
-
4.2.3.3 Upland slough habitats
The predominant effects of mainstem discharge upon the upland slough
habitats between Devil Canyon and the Chulitna confluence dre on
surface area and associated water depths in these sloughs.
Access of fish into the sloughs for spawning and rearing is related to
mainstem discharge levels.A detailed presentation of access into these
habitats and side sloughs by adult salmon is presented in Appendix B.
Low mainstem flows in the Susitna generally have less effect on access
into the upland sloughs than into the side sloughs,but upland sloughs
are not as important as spawning/incubation habitat as are the side
sloughs.The lack of overflow through an upper berm allows sediment
accumulation in these sloughs and also allows beaver dams to become
established.These conditions limit the availability of suitable
spawning substrate.
The influence of mainstem conditions upon rearing and feeding of fish in
the upland slough habitats is similar in nature to the influence in the
side sloughs,but the degree of influence is not as extensive.
Appendices E and F present a discussion of the impact of mainstem flow
upon hydraulic zones and the corresponding relationship with selected
species catch rates at some of the upland sloughs habitats in this reach
of river.These areas may provide a better rearing habitat because of
decreased turbidity,improved cover and stable water velocities.
127
4.2.3.4 Tributary mouth habitats
The predominant influence of mainstem conditions on the tributary mouth
habitats in the Devil Canyon to Chulitna confluence area,similar to the
upland slough habitats,is the local effects of mainstem stage.Mouth
IIperching"can occur on small tributaries if mainstem flow drops to very
low levels.
Access by adult salmon spawners into Portage Creek and Indian River has
been evaluated by Trihey (1982).The study concluded that mainstem flow
variations have little effect on access to these tributaries.Mainstem
flow may affect access of juveniles into tributary mouths,but
quartitative data are not available.
The upstream extent of the backwater zone withi n the tributary is
furthest for those tributaries which have a gradual gradient versus
those whi ch have steep gradient.The backwater area at the mouth of
steep gradient streams is minor.
Data demonstrating these relationship of mainstem stage to tributary
mouth rearing habitats are presented in Appendices E and F for a few of
the tributary mouth habitats in this reach of river.These sites respond
similarly to sloughs but the tributary discharge maintains some of the
habitat at very low flows of the mainstem Susitna.
128
-
4.3 Key findings of fisheries studies downstream of the Chulitna
confl uence
4.3.1 Principal instream habitat types
The general habitat categories which have been described and defined for
the Susitna River drainage downstream of Devil Canyon and upstream of
the Chulitna confluence (ADF&G 1983c)also occur in the area downstream
of the confluence.However,the character and extent of occurrence of
each type below the confluence are different from those areas previously
defined.The following discussion summarizes the primary differences
between the habitat categories in the upper and lower river.
4.3.1.1 Mainstem/side channel
The character of mainstem habitat below the Chulitna confluence differs
substantially from the typical mainstem habitats in the reach of river
upstream from the Chulitna confluence.The main channel of the Susitna
River below the confluence is highly braided with many channels.The
reach of river upstream of the Chulitna confluence has limited braided
channels with an easily distinguishable primary channel.The channels
in the upper t'iver are comparably more stable with minor changes
occurring during high water events.The channels "in the lower reach
often change in morphological character during these high flow events.
The substrate in the lower river mainstem habitats is much less stable
than the more or less armored substrate in the upper river mainstem.
129
In the upper river,side channels are generally easily distinguished
from the main channel that conveys the major portion of the Susitna
River flow.In the lower river,side channels are difficult to separate
from the braided mainstem.Side channel habitat in the lower river is
confined to the smaller channels that are separated from the mainstem
braided area by stable vegetated islands.An example of this type of
habitat is the channel that occurs adjacent to the mouth of Sunshi ne
Creek.This channel generally flows with mainstem Susitna water during
the major portion of the open water season.
4.3.1.2 Side slough
Side sloughs in the lower river are usually much larger than the
equivalent habitat in the upper river.They generally have a more
gradua 1 gradi ent and are often associ ated with tributary confl uences
with the mainstem.Birch Creek Slough is an example of this type of
habitat.Although used by spawning salmon,the percentage of the
surface area within the slough utilized by spawners is much smaller than
in the sloughs upstream of the confluence.This may reflect more
1 imited upwell i ng or substrate 1 imitations associ ated wi th the more
gradual channel gradieht.
4.3.1.3 Upland Slough
Upland sloughs do not appear to be as common in the lower river as
they are in the upper river.The available information in the lower
130
.-
-
river is limited to one site,named Whitefish Slough.This site
dewatered as the mainstem receded in the fall of 1982,suggesting that
mainstem flows may have a much larger influence on these types of
habitat in the lower river.The reason is that,because of a much
broader floodplain in the lower river than in the upper river,the
gradient of upland sloughs is less in the lower river.
4.3.1.4 Tributary
The tributaries are similar to those above the confluence but usually
have lesser gradients.Substantial use by spawning salmon and by
resident species of this habitat type has been documented elsewhere in
the data reports (ADF&G 1983a-d).
4.3.1.5 Tributary mouth
Because of their size,tributary mouth habitats are more important in
the lower river than in the upper river.These habitats are used
extensively by rearing juvenile salmon and are major areas for the
important sport fishing of the salmon species in the system.The mouths
of the Deshka River and of Sunshine Creek are examples of this type of
habitat.
131
4.3.2 Primary species composition and seasonal availability of
instream habitat types
The current level of information on the seasonal distribution and
abundance of fi sh downstream from the confl uence is 1ess well defi ned
than above the confl uence.Generally,the patterns observed upstream
from the confluence are followed downstream.However,the differences
in the composition and extent of the vadous habitat types,and the
differences in the abundance of fish below the confluence suggest
substantial differences from upstream of the confluence.The following
sections highlight the currently known differences.
4.3.2.1 Mainstem/side channel habitats
The primary difference in species composition in the mainstem/side
channel habitats below the confluence is the utilization of the habitat
by Bering cisco and eulachon for migration,spawning,and incubation.
Also,the lower few miles of the river are used by several other species
(for example,Pacific lamprey,other sculpin species,ninespine
stickleback)that do not occur in the upper river.Use of this habitat
for spawning/incubation by chum salmon occurs but is probably of minimal
importance.
Juvenile chum and sockeye salmon possibly utilize the mainstem and side
channels for rearing.The resident fish rearing use in this habitat is
probably similar to that which occurs in the upper river.
132
-
Juvenile coho t chinook t and sockeye and probably most of the resident
fish overwinter in the mainstem/side channel areas.This use is
probably similar to such use in the upper river.However t the number of
fish affected is most likely greater,and includes fish with natal areas
in the upper river as well as from the lower river sloughs and
tributaries.
4.3.2.2 Side slough habitats
The side slough habitats in the lower river are more heavily used by
rearing coho than in the side sloughs of the upper river,probClbly
reflecting population differences.
Spawning/incubation in side sloughs is apparently less prevalent in this
reach of river for chums t but pink salmon spawning appears to be con~on.
4.3.2.3 Upland slough habitats
Very little information is available concerning the characteristics of
the upland sloughs in this area.The data on Whitefish Slough indicate
that these sloughs are less utilized by all fish species as compared to
the upland sloughs in the upper river,with the exception of the
whitefish species and burbot.
133
4.3.2.4 Tributary and tributary mouth habitats
The species composition and availability of the tributary and tributary
mouth habitats is very similar to that which occurs in the upper river.
However,these habitat types are probably of greater importance in this
reach of river due to their greater area.
4.3.3 Influence of mainstem discharge and water quality on
instream habitat types
Our level of understanding of the relationship between mainstem
conditions and instream habitats is much less well defined in the lower
river than in the upper river.Generally,the habitats associated with
the river downstream of the Chulitna confluence more closely resembles
the Chulitna River than the upper Susitna.The overall gradient is
lower in this section of river,which generally leads to greater changes
in wetted area with discharge changes when compared to the upper river.
The following sections highlight the known differences in the influence
of mainstem conditions upon the habitat types in this river section.
4.3.3.1 Mainstem/side channel habitats
The primary flow-influenced habitat effect in this reach of river is the
instability of substrate conditions.The mainstem and side channels in
the lower river change dramatically with high water events.This
instability probably results in the lower availability of this habitat
type for spawning.
134
-
4.3.3.2 Side slough habitats
The general type of impact of mainstem conditions upon this habitat type
is essentially the same as that which occur's in the upper river.
However,the extent of backwater conditions in the sloughs in this reach
of river is generally greater.Bank associated cover for rearing fish
is al so apparently more prevalent in the lower reach.Such cover is
often dewatered with decreases in mainstem flow and the associated
decrease in backwater effects.The use of thi s habi tat by spawni ng
salmon is apparently less common.
4.3.3.3 Upland slough habitats
The limited information from Whitefish Slough indicates that the upland
sloughs in the lower reach of river may be more affected by the mainstem
stage than in the upper river.These sloughs may dewater more
extensively with dropping mainstem flow levels than is the case with the
upper river upland sloughs.
4.3.3.4 Tributary mouth habitats
The effects of changes in mainstem conditions upon tributary mouth
habitats is similar to that observed in side slough mouth habitats in
this lower reach of river.Moderate decreases in mainstem flow levels
often lead to large decreases in backwater areas,which are used
extensively by juvenile salmon and residents for rearing.Adult salmon
often mill in these areas and are subjected to intense sport fisheries.
135
Dewatering of bank associated cover with lower mainstem flows is
probably of greater significance in this lower reach tributary mouths
than in the upper river.
4.4 Limitations of the available data base
This section of the report has summarized the current level of
information as it regards the influence of mainstem conditions upon
habitat availability.Some of the limitations to the available data
base have already been noted above;the following discussion lists some
of the other limitations to this available data base.The general
limitation of little to no information concerning the distribution and
abundance of fish species and the dynamics of habitat conditions during
the winter months is not repeated in the following sections,but does
represent a major limitation.
4.4.1 Habitats in the reach downstream of Devil Canyon to the
Chulitna confluence
Three representative side sloughs have had intensive hydraulic
simulation models developed for predictions of incremental changes on
available spawning habitat for chum salmon.These require additional
discharge and chum salmon utilization data for reliable predictions of
discharge effects on available spawning habitat.To compare these sites
with other sloughs in this reach of river,physical habitat data,such
as discharge and gradient,have been measured at a larger number of
sloughs.Rearing has been evaluated at these sites at representative
136
study areas by monitoring the available surface area of hydraulic zone'>,
such as backwater areas,at different mainstem discharges.These data
have provided a general description of habitat availability as a
function of flow.Micro-habitat availability under variable discharges
and its relationship to rearing fish needs to be determined at a
representative set of sites.
Upland sloughs 6A and 19 have been evaluated for available juvenile
reari ng habi tat.Mi era-habitat ava il abil ity at these type of habi ta ts
as a function of mainstem discharge requires further quantification.
Side channel habitat has been sampled for abundance of spawners and
1imited data has been collected on use by juvenile salmon.Habitat
availability for many of the life stages remains to be completed.
Because of the 1 imited use of the mainstem habitat by spawn'ing or
rearing species,with the exception of selected resident fish,data are
limited to relative abundance information.Quantification of habitat
availability of mainstem areas has not been collected.
Passage of adult salmon into tributaries through the tributary mouth
habitats,as a function of mainstem discharge,has been evaluated for
two of the major tributaries,Indian River and Portage Creek.The
availability of habitat for spawning at these sites has not been
quantified although general availability of juvenile and resident
rearing habitat as a function of mainstem discharge has been examined
for representative sites.
137
....._--------.....-..•_--------------
As the tributaries are not directly affected by mainstem discharge,data
are required only on the distribution and use of micro-habitat by stocks
of resident and anadromous species.This information can be used to
determine the limitations of the mainstem habitats for the particular
life stages of these species.In addition,this information will
suggest if regulated flows of the mainstem have any prospect for
improving available habitat for these species.
4.4.2 Habitats in the reach downstream of the Chulitna confluence
Available data for the lower river are much more 1 imited than in the
upper river.Physical conditions of one side channel area called Chum
Channel and a tributary mouth at Rabideux Creek have been intensively
measured but at a limited range of flows.No attempt has been made to
project available habitat for spawning or rearing fish at these sites.
Juvenile habitat availability has been estimated using the general
hydraulic zone/surface area relationships at five sites.These include
the tributary mouths and associated sloughs at Rabideux Creek,Birch
Creek,and Sunshine Creek.A side slough near the mouth of Goose Creek
and one upland slough,named Whitefish Slough have been evaluated.
Additionally,distributional data and site habitat data have been
collected for spawning eulachon,Bering cisco,and limited chum salmon
spawning areas but availability of this habitat has not been estimated.
The quantification of rearing micro-habitat and of spawning habitat for
eulachon,Bering cisco,and chum salmon has not been completed.Basic
data on the distribution,rearing,and spawning of most of the species
138
in the lower river are quite limited and overall knowledge is probably
an order of magnitude below the 1eve 1 of understandi ng of the upper
river.Virtually nothing is known about the several other species (for
example,ninespine stickleback,Pacific lamprey,pond smelt)which
occupy the lower few miles of river,but which have not been collected
by this program.
Important questions,such as the degree of growth and utilization of
rea ring habitat by outmi grati ng chums,the di stri bution of spawni ng
adults in peripheral areas,and the rearing habitat of other resident
and juvenile salmonids,have not been answered.
139
5.0 CONTRIBUTORS
PRIMARY AUTHORS
(l)TEXT
Sections 1,2,and 3
Section 4
(2)APPENDICES
Appendix A
Appendix B
Appendix C
Appendix 0
Appendix E
Appendix F
Appendix G
Appendix H
Appendix
Appendix J
Appendix K
REPORT COORDINATORS
140
Dana Schmidt
Allen Bingham
Fredrick M.Thompson
Bruce M.Barrett
E.Woody Trihey
Len Vining
Christopher Estes
Sheryl Salasky
Rick Sinnott
Andrew Hoffmann
Rick Sinnott
Kim Sylvester
Andrew Hoffmann
Christopher Estes
Bob Marshall
Stephen Hale
Paul Suchanek
Stephen Hale
Stephen Hale
Dana Schmidt
Paul Suchanek
Stephen Hale
Gene Sandone
Joe Sautner
Dana Schmidt
Drew Crawford
Stephen Hale
Andrew Hoffmann
EDITORS
DATA PROCESSING
DRAFTING
TYPING
141
Bruce M.Barrett
Larry Bartlett
A11 en Bi ngham
Drew Crawford
Christopher Estes
Stephen Hale
Andrew Hoffmann
Bob Marsha 11
Dana Schmidt
Paul Suchanek
Thomas W.Trent
E.Woody Trihey
Allen Bingham
Ga il He"j neman
Donna Buchholz
Kathrin Zosel
Alice Freeman
Sally Donovan
Ann Reilly
Peggy Skeers
Loretta Channell
Joyce Godin
Lynne Watson
6.0 ACKNOWLEDGEMENTS
Funding for this study was provided by the 'State of Alaska,Alaska Power
Authority.
Special appreciation is extended to Nikki Newcome (ADF&G)for providing
technical support to the computer modeling portion of the hydraulic
studies and to Beverly Valdez (Arctic Environmental Information and Data
Center)for computer plotting stage/discharge curves.Appreciation is
150 extended to those individuals not mentioned here who assisted with
this project.
142
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Department of Fish and Game,Habitat Division,
65 pp.
Arctic grayling
USFWS by Alaska
Anchorage,Alaska.
1981.Freshwater habitat relationships.Dolly Varden
(Salvelinus malma).Report prepared for USFWS by Alaska Department
of Fish and Game,Habitat Division,Anchorage,Alaska.38 pp.
Raleigh,R.F.,and T.Hickman.1982.Habitat suitability index models:
Rainbow trout.(unpublished draft).Western Energy and Land Use
Team,U.S.Fish and Wildlife Service,Ft.Collins,Colorado.
Roberts,T.H.,and L.J.H.O'Neil.1983.Status and source of models
and literature reviews (unpublished report).U.S.Army Corps of
Engineers Waterways Experiment Station.9 pp.(Includes
references to literature reviews and/or habitat suitability models
for other species that occur in the Susitna River.These reports
are in various stages of completion and have not been reviewed by
us).
U.S.Fish and Wildlife Service.Coho salmon (Oncorhynchus kisutch).
(Revi ew draft of habitat sui tabil ity report).Western Energy and
Land Use Team,Ft.Collins,Colorado.
150
u.s.Fish and Wildlife Service.Sockeye salmon (incomplete draft of
habitat suitability report).USFWS National Fishery Research
Center.Anchorage,Alaska.
151
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9.GLOSSARY OF COMMON AND SCIENTIFIC NAMES
Scientific Name
Entosphenus tridentatus (Gairdner)
Lampetra japonica (Martens)
Coregonus laurettae (Bean)
Prosopium cylindraceum (Pallas)
Coregonus pidschian (Gmelin)
Salmo gairdneri (Richardson)
Salvelinus malma (Walbaum)
Oncorhynchus gorbuscha (Walbaum)
Oncorhynchus tshawytscha (Wa"lbaum)
Oncorhynchus keta (Walbaum)
Oncorhynchus kisutch (Walbaum)
Oncorhynchus nerka (Walbaum)
Thymallus arcticus (Pallas)
Thaleichthys pacificus (Richardson)
Esox lucius (Linnaeus)
Catostomus catostomus (Forster)
Lota lota (Linnaeus)
Gasterosteus acu1eatus (Linnaeus)
Pungitius pungitius (Linnaeus)
Cottus cognatus (Richardson)
P1atichthys stellatus (Pallas)
152
Common Name
Pacific lamprey
Arctic lamprey
Bering cisco
Round whitefish
Humpback whitefish
Rainbow trout
Do 11y Va rden
Pink sa"lmon
Chinook salmon
Chum salmon
Coho salmon
Sockeye salmon
Arctic gray1 ing
Eulachon
Northern pike
Longnose sucker
Burbot
Threespine stickleback
Ninespine stickleback
Slimy sculpin
Sta rry flounder