HomeMy WebLinkAboutAPA3156JMS w I BROOKS) CXJ1>1ISSIONER
DIYISIOn OF SPORT FISifl
FEDER~l AID IN
FISH RESTORATION
JULY 1, 1973 TO JUNE 30.1974
STUDY G-Ill
LAKE AND STREAM INVESTIGATIONS
JOB G-111-G
A STUDY OF A TYPICAL SPRING
FED STREAM OF INTERIOR ALASKA
GARY A. PEARSE
SUBPORT BUILDING
JUNEAU, AK. 99801 ~ • . , .
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Volume 15
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STATE OF ALASKA
WILLIAM A. EGAN, GOVERNOR
Annual Performance Report
For
LAKE AND STREAM INVESTIGATIONS
A Study of a Typical Spring
Fed Stream of Interior Alaska
by
Gary A. Pearse
ALASKA DEPARTMENT OF FISH AND GAME
James W. Brooks, Commissioner
DIVISION OF ·SPORT FISH
Rupert E. Andrews. Director
Study G-Ill
Job No. G-III-G
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, $ 8'
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11\,-o. Z I~
Howard E. Metsker, Chief, Sport Fish Research
ARLIS
Alaska Resources
Library & Information Services
Anchorage.A1aska
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Volume 15
TABLE OF CONTENTS
ABSTRACT
RECOMMENDATIONS
OBJECTIVES
BACKGROUND
TECHNIQUES USED
FINDINGS
Water Quality
Species Present and Distribution
Standing Crop
Grayling Life History
Round Whitefish Life History
Silver Salmon Life History
Creel Census
LITERATURE CITED
Study G-III
Page No.
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Volume 15 Study No. G-1 I I
RESEARCH PROJECT SEGMENT
State: ALASKA
Project No.: F - 9 - 6
Study No . : G -III
Job No.: G -III - G
Name: Sport Fish Investigations
of Al a ska.
Stud y Titl e : LAKE AND STREAM INVES TIGATIONS
Job Titl e : A Study of a Typical Spring
Fed Stream of Interior Alaska.
Period Covered: July 1, 1973 to June 30, 1974.
ABSTRACT
Data collected during 1972 and 1973 as part of renewed studies of Interior
Alaska spring -fed streams is presented. The study area, principally the
Delta Clearwater River, includes several popular sport fisheries for Arc-
tic grayling, Thymallus arcticus.
Water temperatures in the spring-fed systems ranged from 0 .5°C to 8.5°C .
High levels of hardness and alkalinity were recorded.
Main fish species present were Arctic grayling, round whitefish, Prosopium
cylindraceum, and silver salmon, Oncorhynchus kisutch.
Estimates of standing crop for the Delta Clearwater River showed 6.7 kg per
hectare for grayling and 56.9 for round whitefish. Standing crop estimates
of round whitefish in two sections of the Tanana River averaged 84 kg per km.
Data are presented on interstream .and intrastream migration patterns. Abund-
ance estimates were determined by both the Schnabel and Schumacher-Eschemeyer
methods, the latter showing an estimated 2,267 grayling and 13,611 round
whitefish in the Delta Clearwater River.
Life history information regarding length frequencies and distribution,
length-weight relationship, condition factors, age and sex composition,
and maturity for Arctic grayling and round whitefish is presented.
Limited data on food habits and a faunal list are presented.
An estimated 3,322 silver salmon spawned in the Delta Clearwater River
during 1973. Salmon escapement estimates for surrounding systems are also
presented. Certain aspects of silver salmon life history are discussed.
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RECOMMENDATIONS
It is recommended that this job be terminated with the exception of the
following phases which should be incoroorated into other existing jobs
in the area:
1. Introduce young-of-the-year Arctic grayling in certain
sections of the Delta Clearwater system.
2. Develop methods for increasing the sport harvest of round
whitefish in the Tanana River drainage waters.
3.
OBJECTIVES
1.
2.
3.
4.
5.
Complete a short-term food competition study between round
whitefish and Arctic grayling.
To determine fish species present, distribution, inter-
stream and intrastream migration, and abundance in the
Delta Clearwater system.
To ~etermine life history information such as length,
weight, condition, age, growth rate, sex, and maturity
composition in the Delta Clearwater system.
To determine production of fish species within various
sections of the Delta Clearwater system.
To determine spawning locations, timing and fecundity
of fish species in the Delta Clearwater system.
Food habits studies will be conducted to determine dis-
tribution and species diversity of aquatic insects and the
relationship to fish food preferences in the Delta Clear-
water system.
6. To obtain information on effort, catch success, and sport
fish harvest from anglers fishing the Delta Clearwater system.
BACKGROUND
Studies of typ1cal Interior Alaska spring-fed streams were initiated in
1952 by the U.S.F.&W.S. as part of the Arctic grayling life history study.
From 1952 to 1958 studies were conducted. on age and growth, migration,
food and spawning habits of grayling. The study emphasized migration
habits of grayling within the Tanana River watershed and developed
various tagging techniques. Results of these studies were presented
as Quarterly Progress Reports of Federal Aid in Fish Restoration, F-I-R-I,
to F-I-R-8.
3
In 1959, studies on the Delta Clearwater and nearby river systems were
divided into the determination of stocks, migration (intrastream and
interstream), and angler success. The above studies have been continued
intermittently until the present and results published in the annual
Department of Fish and Game Federal Aid in Fish Restoration Reports.
Angler demand for stream fishing continues to be substantial, although
some fishing pressure has been diverted toward the managed lakes in
the area.
The present program was designed to bring to date information on the
status of fish species present in the Delta and Richardson Clearwater
rivers, and other spring-fed systems in the Tanana drainage (Figure 1).
The Delta Clearwater River, the main study area, is situated approximately
8 miles northeast of Delta Junction (Figure 2). Access is either through
two roads which branch off the Alaska or Richardson highways, or up
the Tanana River from Big Delta. The Delta Clearwater River drains an
area of approximately 350 square miles, drawing heavily on groundwater
as its source. Fairly constant levels, flows, and water temperatures
characterize this and other Interior Alaskan spring-fed systems. The
other study area, the Richardson Clearwater River, drains an area of
approximately 48 square miles and possesses similiar qualities. It enters
the Tanana River from the west approximately 40 miles below the confluence
of the Delta and Tanana rivers.
TECHNIQUES USED
Fish species studied for population, migration, and life history data were
captured either by an alternating current shocker boat described by Van
Hulle (1968) and Roguski and Winslow (1969), or by using a 50' seine.
Rearing species were captured with a back-pack mounted, pulsed DC electro-
shocker.
Number FD-67 (Floy Tag Company) internal anchor tags were inserted in the
dorsal musculature on fish over 150 mm.
Migration was determined from tagged fish recaptures. Population estimates
were accomplished by both the Schnabel and Schumacher-Eschmeyer mark and
recapture methods (Ricker, 1958). (The estimates of standing crop were
calculated by separating the population estimate for an area into the
number of fish in each 10 mm length group present. The average weight
for. each 10 mm length group multiplied by the estimated number summed
for all length groups gave the standing crop estimate.)
A random subsample was autopsied for life history information. Fork lengths
in millimeters, weights in grams, stomach, and gonad samples were obtained.
The Delta Clearwater River was divided into uniform sections to facilitate
sampling and habitat studies.
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Fairbanks
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Richardson Clearwater
River
Scale 1=250,000
Miles
F3 F3 F3 Kilometers
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Tanana
River
Delta
River
r--,
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Distance Key
Delta Clearwater to Clearwater Lake
Delta CIE!arwater to Goodpaster River
Delta Cl•~arwater to Shaw Creek
Delta Cl·earwater to Richardson Clearwater
Delta Clearwater to Section 80
Delta Clearwater to Section 81
' ' Clearwater
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'D Delta: Clearwater ~ • ~Lta River
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FIGURE I. TANANA-CLEARWATER STUDY AREA --
mi
2
8
31
40
14
3
km
3
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49
64
22
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REMINGTON ROAD
NISTLER ROAD
FIGURE 2. DELTA CLEARWATER RIVER AND SAMPLE SECTIONS
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Spawning locations and timing were determined visually. Aquatic insects
were collected by Surber sampler and manual methods.
Angler interviews were conducted to determine catch and effort.
Water chemistry determinations were made with a Hach AL-36 B drop titration
kit.
Water velocities were determined by the velocity head rod method.
Scales from captured fish were taken for age determination. The scales
were cleaned, mounted on gummed cards, and heat pressed onto acetate sheets.
An Eberbach console microprojector was used for determining the age of
sampled fish species. Grayling scales were aged along the dorsal radius,
while round whitefish and silver salmon were aged along the anterior field.
Measurements of total scale radius and focus to annuli values were taken
from randomly sampled grayling and round whitefish scales to determine
back-calculated lengths. The linear formula used was that of Rounsefell,
1953, p. 324, and employed the formula: L1 = C + sl (L -C)
where L1 Length at annulus formation -unknown
S 1 = Scale radius from focus to annulus
L Length at capture
S = Total scale radius
C Length at scale ·formation
s
Tack (1971) reports grayling first form scales at a length close to 35 mm.
From a sample of rearing round whitefish taken on the Goodpaster River in
mid-July of 1973, it was shown that the largest size at which scale forma-
tion occurred was also 35 mm. Therefore, this length at scale formation
(C) was taken for both species. Back calculations were carried out
on a Friden 1155 computer.
FINDINGS
Water Quality
The yearly water quality and temperature values for the Delta Clearwater
River are shown in Table 1. Temperatures ranged from a winter low of
0.5°C to a summer high of 8.5°C. Daily warming fluctuations induced by
cloud cover and stream section were common, with the warmer water found
further downstream. Winter icing occurs only in slow stretches below
section 14, and in some lower sections of the left fork. Dissolved
oxygen, pH, and C02 values remain fairly stable and always acceptable.
Hardness and alkalinity average 157 ppm and 140 ppm respectively in the
main river. The average hardness and alkalinity in the left fork (188
and 165 ppm) are higher than in the right fork (137 and 143 ppm). The
springs that feed the headwaters of the right fork maintain a constant
2°C temperature with dissolved oxygen at 8 ppm, hardness and alkalinity
at 188 and 171 ppm, and C02 at 25 ppm year round. The main water source
is the Granite Mountains to the south.
7
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TABLE 1. Water Quality and Flows From the Delta Clearwater River,
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1972-1973.
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H2 0 CC) DO Hardness Alkalinity C0 2 Flows
Year Month Temp. (ppm) pH (ppm) (ppm) (ppm) (cfs) L
1972 Oct.* 2.0 17 8.0 188 171 20 [ 1972 Oct.** 1.0
1972 Dec.*** 1.0 r 1973 Jan.*** 1.0 20 8.5 137 120 15
1973 Feb .. *** 0.5 19 8.0 154 137 15
L 1973 Mar.** 2.0 12 7.7 171 137 10
1973 Mar.*** 1.5 21 8.0 171 154 15 r--
1973 Mar.**** 3.0 L
1973 Apr.* 3.7 18 8.0 188 154 80 [ 1973 Apr.** 4.1 20 8.0 102 137 336
1973 Apr.*** 3.6 r 1973 Apr.**** 5.7 c.
1973 May** 5.3
1973 May*** 5.4 [
1973 June* 6.5 11 8.5 188 171 15 101
1973 June*** 8.5 13 8.7 171 137 10 710 [
1973 June**** 14.0
1973 July** 7.0 [
1973 July*** 8.5 12 8.4 154 154 15
1973 Aug.** 4.5 L
1973 Sept.*** 3.5
1973 Oct.* 1.5 r
1973 Oct.** 2.0 L
1973 Oct.*** 2.0 [ 1973 Nov.** 2.0
*Left Fork L **Right Fork
***Main River L **~*Mile 1 Slough
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Table 2. shows similar water conditions found in the Richardson Clearwater
River.
The high values for hardness and alkalinity, constant temperatures and
generally year round ice-free conditions make the Delta Clearwater and
similar stream potentially excellent fish producers.
TABLE 2. Water Quality and Flows From the Richardson Clearwater River,
1973.
H2 0 DO Hardness Alkalinity C0 2 Flows
Month Temp. (ppm) pH (ppm) (ppm) (ppm) (cfs)
(oC)
August 6.0 12 8.5 137 137 5 340
October 3.5 11 8.0 171 137 5
Species Present and Distribution
Fish species either observed or captured in the Delta Clearwater River
consist of Arctic grayling, Thymallus arcticus; round whitefish, Prosopium
cylindraceum; humpback whitefish, Coregonus pidschian; least cisco, C.
sardinella; longnose sucker, Catostomus catostomus; slimy sculpin, Cottus
cognatus; and silver salmon, Oncorhynchus kisutch. Northern pike, Esox
lucius and chum salmon, 0. keta have been reported in the lower sections,
however none were observed.----
In 1973, round whitefish were first observed in Section 1 and in Mile 1
Slough on April 10. Small numbers of grayling were also present. None of
these species were observed upstream prior to that date. These fish entered
from the Tanana River, a possible overwintering habitat. The water tempera-
ture had by that time risen to 3.6°C from a February low of 0.5°C. Both
of these species were present in mid-December the previous year, and ap-
parently left the stream in the interim period.
Round whitefish in the Delta Clearwater River were either captured or ob-
served in Section 1 through 14 of the main river, 15 through 17 of the
left fork and 15 through 20 of the right fork. Grayling were also present
in these sections. The numbers in the left fork were minimal compared with
the right fork for both species.
·Silver salmon rear in the Delta Clearwater River for up to two years, at
which time they smolt and leave. Adults return to spawn the following year
in early September.
9
Silver salmon occupied rearing habitat in spring areas and stream margins
throughout the entire Delta Clearwater River system. They were captured
as far up as the springs which feed the headwaters of the river, approximately
20 miles from the mouth. Adult salmon use the entire system as a spawning
area.
Chum salmon utilize Section 1 and Mile 1 Slough as a spawning area.
Least cisco and humpback whitefish appeared as incidental captures in mid-
May. They were absent in future sampling e.fforts and were never captured
above Section 2.
During a two week period beginning July 23, approximately 500 suckers were
observed in the lower three stream sections. Water temper~ture was 8.5°C.
There is no information on the duration of sculpin presence or distribution
in the Delta Clearwater River.
Round whitefish, grayling, silver salmon, and chum salmon were either observed
or captured in the Richardson Clearwater River.
Round whitefish and grayling were found only in the lower 4 miles of the
Richardson Clearwater River. Silver and chum salmon were observed to range
3 miles further upstream.
Standing Crop
Estimates of standing crop were derived for Arctic grayling and round white-
fish in the Delta Clearwater River and for round whitefish in Sections 80
and 81 of the Tanana River.
Table 3 presents the standing crop for grayling in the Delta Clearwater
River. The date of the population estimate (8/16/73) removes the effect
of previous angler induced mortality.
Table 4 presents a similar estimate for round whitefish in the same system.
Round whitefish are six times as abundant and represent 8.46 times the
biomass of grayling in the Delta Clearwater River. The total biomass of
round whitefish and grayling in this river equals 7,569 kg or 16,690 pounds.
This equals 63.6 kg per hectare or 56.6 pounds per surface acre.
Estimates of round whitefish standing crop in Sections 80 and 81 of the
Tanana River are presented in Table 5. No data are available on river
surface area.
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TABLE 3. Standing Crop Estimate, Arctic Grayling, Sections 2-17, Delta
Clearwater River, August 16, 1973.
Surface
Area
Hectares
119
Acres
295
Population
Estimate*
2,267
*Schumacher-Eschmeyer estimate
**800 kg or 1,764 pounds.
Number/Surface
Area
Hectares Acres
19 8
Standing
Crop**
kg/hectare lb/acre
6.7 5.9
kg/km. lb/mile
32.0 110.3
TABLE 4. Standing Crop Estimate, Round Whitefish, Sections 2-17, Delta
Clearwater River, August 15, 1973.
Surface Population Number/Surface Standing
Area Estimate* Area Crop**
Hectares Acres Hectares Acres kg/hectare lb/acre
119 295 13,611 114 46 56.9 48.5
kg/km lb/mile
270.8 932.8
*Schumacher-Eschmeyer estimate
**6769 kg or 14,926 pounds
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TABLE 5. Standing Crop Estimates, Round Whitefish, in Certain Sections
of the Tanana River, April, 1973.
River Population Section Length Standing Crop Total
Section Estimate* km mi. kg/km lb/mi. (kg)
80 3,378 3.2 2 306.1 1,079. 5 979.4
81 14,662 6.0 4 1,128. 2 3,731. 3 6,768. 9
*Schumacher-Eschmeyer estimate
Grayling Life History
Intrastream Migration:
The summary of grayling interstream migrations based on 1973 tagged fish
recaptures are shown in Table 6. The trend of grayling to migrate within
the study area with certain specific interchanges follows a pattern simi-
lar to that summarized by Shallock and Roguski (1967).
TABLE 6. Interstream Grayling Migration Summary, Tanana Drainage, 1973.
Location Date Location Date Movement
Tagged Tagged Recaptured Recaptured mi. km.
Delta Clearwater R. 5/16i73 Clearwater Lake 7/7 . 12 19
Delta Clearwater R. 5/18/73 Clearwater Lake 7/16 4 6
Delta Clearwater R. 6/26/73 Goodpaster River 9/15 33 53
Goodpaster River 8/21/70 Clearwater Lake 7/8 6 10
Goodpaster River 8/23/72 Richardson Clear. R. 7/15 30 48
Goodpaster River 5/9/73 Delta Clearwater R. 6/29 19 30
Goodpaster River 5/9/73 Delta Clearwater R. 7/15 19 30
Chen a River 7/29/68 Richardson Clear. R. 8/1 90 144
Lower Tangle Lake 6/28/69 Delta Clearwater R. 7/3 111 178
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The Goodpaster River and Shaw Creek are spawning areas, whereas few grayling
reproduce in either of the Clearwater River systems. Hence, rearing grayling
emigrate from these spawning rivers and enter the Tanana River, whereupon
a migration to summer feeding areas, such as the Delta and Richardson Clear-
water rivers, takes place.
It has been previously shown that fish migrating to another system after
tagging are most likely to be recovered the following year.
Of interest is the recapture of a grayling in the Richardson Clearwater
River that had been tagged five years previously in the Chena River, near
Fairbanks. This amounted to a movement up the Tanana River of 144 km
(90 mi.). The recapture in the Delta Clearwater River of a grayling
tagged in 1969 in Lower Tangle Lake, that moved down the Delta River,
then up the Tanana River, emphasized long range movements.
A single grayling tagged in the Delta Clearwater River in June 1973 was
later recaptured up the Goodpaster River the following September.
Intrastream Migration:
Table 7 summarizes the mark and recapture efforts on Arctic grayling in
the Delta Clearwater River during 1973. Of the 411 fish tagged, 65 (16%)
were later recaptured. ~~glers caught a minimum of 23 (6%). The number
tagged amounts to approximately 20% of the estimated number of grayling
in the stream (2,267).
TABLE 7. Mark and Recapture Summary of Grayling Tagged jn the Delta
Clearwater River, 1973.
Total Number Tagged 411
RecaEture Summary
Method Number (%) Location
Electroshocker boat 39 9 Delta Clearwater River
Returned Angler Catch 23 6
62 15
Electroshocker Boat 2 0.5 Clearwater Lake
Returned Angler Catch 1 0.2 Goodpaster River
3
Total 65 16
General movement trends are shown in Figure 3. As mentioned above, grayling
entered the Delta Clearwater along with the round whitefish in early April.
These fish were all less than 290 mm in fork length. Of those tagged in
April (15), only one was later recaptured upstream. There were few re-
coveries of grayling tagged in May. However, those grayling tagged in
June showed a major downstream movement when recaptured in July, August,
and October. Whether this movement was normal or induced by capture
and handling shock is not known. The small number of recaptures precludes
a statement of conclusive trends, especially with the possibility of upset
from sampling.
Visual observations tend to show that the smaller grayling entered the
river in April. Larger (greater than 300 mm) grayling entered in mid-May
and June and migrated upstream to establish themselves in prime feeding
habitat in Sections 9 through 17. Observations in late August or Septem-
ber failed to show the abundance of these fish in the upper stream sec-
tions, suggesting a downstream trend of movement in the fall. Some grayling
lingered through mid-winter (1972), however all were absent in March of
the following spring (1973).
A total of 71 grayling was tagged in the Richardson Clearwater River the
first two days in August, but no effort was made to assess intrastream
movement.
Abundance:
Estimates of grayling abundance in the Delta Clearwater River by the
Schnabel and Schumacher-Eschmeyer methods are shown in Table 8. Low
recapture success, i.e., 12 recaptures for the June and 15 for the August
estimates, necessitated the two separate estimates. The June estimate,
which focused on the relative concentration of grayling in the upper stream
sections, totaled 1,451 for the Schnabel method and 1,454 for the Schumacher-
Eschrneyer method.
TABLE 8. Estimates of Grayling Abundance in the Delta Clearwater River,
1973.
Sample River Schnabel 95% GR per Schumacher-95% GR per
Dates Sections Estimate CI ml. km. Eschemeyer CI mi. km.
Estimate
6/20-29 10-17 1,451 961-4,311 181 132 1,454 1,189-1,871 182 121
8/13-16 2-17 2,169 1,489-5,188 136 87 2,267 1,405-5,865 142 91
14
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UP DNNM
MAY
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UP ON NM UP ON NM
JUNE JULY
UP DNNM
AUGUST
UP ON NM UP ON NM
SEPTEBER OCTOBER
MONTH RECAPTURED
~igurc 3. The Restricted* Number of Grayling Recaptured that Moved
llp (UP), Down ( DN), or Showed No Movement (Nl\1) in the
Delta Clearwatet· River, 1973.
*Excludes Recaptured withjn a Week of Previous Captun·
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Delta Clearwater River ~
n=422
x=355mm ~
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1--
,..-----n·, -l I 1-
100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440
109 !29 149 169 189 209 229 249 269 289 309 329 349 369 389 409 429 449
Fork Length (mm)
.... 7
1-6
~ 5
-4
3
-2
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FIGURE 4. LENGTH FREQUENCY OF ELECTRO-FISHED ARCTIC GRAYLING FROM
THE DELTA CLEARWATER RIVER, 1973.
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t--0 -c
Cll
(,) ... • a.
The population estimate (2,267) for the majority of the Delta Clearwater
system barely exceeds the total number of grayling tagged (2,160) in 1960
(Reed, 1964).
Length Frequencies:
The length frequency distribution of 422 grayling captured during 1973 in
the Delta Clearwater River is shown in Figure 4. The mean length is 355 mm.
Except for peaks at 230 -250 mm, the distribution of fish lengths is smooth
to the peak at 330-339 mm (7% of total). After this group, the numbers
of larger fish decrease rapidly. This may be due to angler pressure and
selectively, or natural mortality. However, the steepness of the decline
would not favor the latter.
Table 9 presents comparative length frequencies of grayling sampled in
the Delta Clearwater River from 1960 to 1973. Fish sampled in 1973 dif-
fered in length group abundance from those,captured in previous years.
Length groups from 165 -264 mm were at a lower percentage, length group
percentage for 265 -314 mm fish was normal, and fish above 315 mm fork
length comprised a higher percentage than recorded before.
The reason for the change in length frequencies is not readily apparent.
The sampling method used in 1973 (Electroshocker boat) may have been selec-
tive for larger sizes as opposed to hook and line or seines used in earlier
years.
The length frequency distribution shown in Figure 5 for fish captured in
the Richardson Clearwater River displays marked gaps in the length groups
and a general absence of fish greater than 319 mm in fork length. The
sample size (85) may not reflect the actual condition as would one with
more samples. However, large fish (greater than 319 mm) were absent, as
were fish with a fork length less than 220 mm.
Length -Weight Relationships:
The length-weight relationship of Arctic grayling captured in the Delta
Clearwater River during two sample periods is shown in Figure 6. The
standard formula of weight = a x (fork length)n was used; values for a
n being determined empirically. The concept of weight versus length
being a cube function is followed closely. Grayling captured in May
(N = 27) weighted less at a given length than grayling captured later in
the summer (N = 48). The weight increase was due to good food availability
and gonad development.
Condition Factors:
The condition factors were determined by the formula K = weight divided
by fork length3 x 105 and are shown for grayling from the Delta Clear-
water River in Table 10. The weights used were those estimated by the
17
TABLE 9. Length Frequency of Grayling, Captured in the Delta Clearwater River. 1960-1973.
·----------·-----
Length
Class 1960 1961 1962 1963 1964 1965 1966 1973
(mm) No. (%) No. (%) No. (%) No. (%) No. (%) No. (%) No. (%) No. (%)
165-214 418(20.1) 61(19.1) 371(43.2) 51(10.4) 106(29.3) 58(20.6) 69(17.9) 30(7.4)
215-264 923(44.1) 105(32.8) 544(50.1) 155(31.6) 93(26.7) 96(43.2) 224(58~0) 89(21.6)
265-314 564(26.9) 75(23.4) 116(10.7) 193(39.3) 96(26.5) 90(32.0) 77(20.0) 80(19.4)
315-364 165(7.9) 68 (21. 3) 45(4.1) 69(14.1) 48(13.3) 25(8.9) 14(3.6) 138(33.4) .......
00
365-414 23(1.1) 10(3.1) 10(0.9) 22(4.5) 17(4.7) 12(4.3) 2(0.5) 67(16.2)
415-464 _1 (0. OS) _1 (0. 3) ---_1 (0. 2) _?_(0.6) ------------_9 (2. 0) ---
2,094 320 1,086 491 362 281 386 413
;
r--'1 r--; r--J r--1 r! rJ l'i rJ r-l r---,
' J rl r-1 r-; l'i r----1 ~
Mean
Percent
1960-66
21.6
39.5
25.5
10.5
2.7
0.2
..---,
J
...----,
) ~
IO-Richardson Clearwater River
9-
8-
:::r::
CJ)
1.1.. 7-
1.1..
0 6-
0::
LLJ
Ill 5-~ z 4-
-t--
(n=s5)
(i=2SO)
-
-
r--
-
-
-
I I I I I I I I I I I I I I I I I I I I I I .1 I I I .1 I I I ().1 ().1
<D 1\) N N ~ N ~ ().1
0 ~ g -.J CD 0 ().1 g ~ 0 ~ c3 0 0 0 0 0
I I I I I I ~ I I I I I I I I <D -01 Ul -.J ~ ~ ~ $ w ~ t/3 -.J
<D <D <D <D <D <D CD
FORK LENGTH ( mm)
r ! , 1 rr r ' ., ',
0
'J,
~
•_, --~
H2 ~
Of;
~
!-II :;....,
:1l
~ . --
(.;
+-' u
h .....
--::;
Q
~
·.r.
+
0
h
+-' u (J)
Q ,.!
,..., 1'1')
WJ ['-..
(J) + -0
~
;:.., h
'_) Q
:: :--c.. ·-:::; -~
~2
:;;-
Q h ::-. G)
+-'
C"j ..c 3:
+-' h
ct, r. :: 8
I I I
~ ~
0
I I
Q ,...,
l_;
Lr.
$ <D 8
~~
length-weight relationship described in Figure 6; fork lengths were taken
at the mid-point of 20 mm groups. Hence, the K values describe calculated,
average condition values. The higher the K value the greater the calculated
weight at a given length.
TABLE 10. Relative Condition Factors (K = W/FL 3 x 10 5 ) for Arctic Grayling
Samples in the Delta Clearwater River, 1973.
Sampled Period
Length Group (mm) 4/11-16 5/14-10/10
100-119 0.954 1. 091
120-139 0.947 1.095
140-159 0.943 1.099
160-179 0.938 1.103
180-199 0.934 1.107
200-219 0.929 1.110
220-239 0.926 1.113
240-259 0.923 1.115
260-279 0.920 1.117
280-299 0.916 1.120
300-319 0.915 1.122
320-339 0.913 1.124
340-359 0.911 1.126
360-379 0.909 1.127
380-399 0.907 1.129
400-419 0.905 1.130
420-439 0.903 1.132
440-459 0.901 1.133
20
[
[
I
L
[
r,
L
[
[
[
[
[
[
L
L
L
-,
;
-~
_.
900
800 4/11-16173 W=ll57xi0-5 (FL2.959) N=27 I
' I -·-
5114-10/10/73, W=9.601x 10-6 (fl3.027)N=48
700 I
/
600 I
I
500 I
I -:£ 4J I (!)
1-I :l:
(!)
Lij
3: I
300 I
I
I
200 ~/
'/
100 '/
~
~
0~--~~T---r---~~r-~--~---r---r--~~
0 100 200 300 400 500
FORK LENGTH (MM)
lt"-''l'l' b. Length--Weight l~cL..ttivnshi! of ArctiL· ;_;ra\·ling (Scxc,
LomhincJ )Delta Clean,atcr River. 1~)7:;.
21
In the April grayling sample, condition factors decreased with increasing
fork length. A possible reason is that the larger, potential spawning
sizes (greater than 300 mm) lose more weight proportionally in reproductive
products than smaller fish lose in just a winter feeding. The larger grayling
would have spawned just prior to capture. Grayling captured during the
summer period showed an increase in weight for a given length; the in-
crease being greater for larger fish.
TABLE 11. Age Composition and Observed Length-Age Relationships of 237
Arctic Grayling Electrofished in the Delta Clearwater River,
1973.
Fork Length
(mm)
100-119
120-139
140-159
160-179
180-199
200-219
220-239
240-259
260-279
280-299
300-319
320-339
340-359
360-379
380-399
400-419
420-439
440-459
No. of Fish
I
3
•
3
II
1
4
5
III
2
6
8
14
7
1
38
IV
1
8
12
15
10
5
2
53
v
4
7
13
10
4
38
VI
1
1
2
19
20
12
1
1
57
VII
4
9
10
8
VIII
3
1
2
2
2
IX
1
1
X XI+
1
1
Age Comp. 1.3 2.1 16.5 22.4 16 24.1
31
13. 1
10
3.8 0.4 0.4
(%)
Avg. Length
(mm)
S.D.
115 160 222 268 311 346
6 19 24 26 23 22
22
366 402 456 425
25 29
[
[
I L
[
[
[
[
f'
L
[
[
[
[
[
[
I l~
[
[
[
[
[
[
r
!
[
[
[
[
F
I L~
[
[
"
L
Age Composition and Lengths at Age:
The age compos1t1on and observed length-age relationship of 237 Arctic
grayling from the Delta Clearwater River is shown in Table 11. Sample
sizes of age II and younger grayling are minimal, as are those of age IX
and older. The almost total absence of recruitment within the Delta
Clearwater system means that fish presence is due solely to inmigration.
Therefore, the age III fish represent the first influx of grayling that
have left rearing habitat elsewhere. By age VIII, grayling are reduced
in numbers through fishing and natural mortality.
Table 12 for the Richardson Clearwater grayling depicts the similar composi-
tion and length relationship as shown above. There is an almost complete
absence of age II and younger fish. However fish in the older age classes
decrease in number of age VI fish as opposed to decrease at age VIII in the
Delta Clearwater. This absence of larger fish is also shown in Figure 5.
The average calculated size of Richardson Clearwater grayling at age IV and
older is less than that of similarly aged grayling captured in the Delta
Clearwater River.
Back-Calculated Lengths at Age:
Due to the absence of younger age groups in both grayling and whitefish
sampled, back-calculated lengths were computed to supplement the empirical
data above. The body-scale relationship for both grayling and round
whitefish was plotted and indicated a linear relationship.
Back-calculated lengths
presented in Table 13.
Growth increments begin
Back-calculated lengths
for grayling taken in the Delta Clearwater River are
Average annual growth increments are also pre·sented.
a decline after age III and stabilize by age VI.
agree closely with empirical age data in Table 11.
Richardson Clearwater grayling back calculated lengths are shown in Table 14.
Annual growth increments decrease after.age III.
Figure 8 shows the comparison of back calculated fork lengths and growth
increments by age for grayling in the Delta Clearwater and Richardson
Clearwater rivers. The mean fork length at any age is greater for Delta
Clearwater grayling, as are annual growth increments below age VI.
Length Distribution:
The length distribution of Arctic grayling by stream section for the
Delta Clearwater River is presented in Table 15. Assuming catch rate is
proportional to relative numbers, the sample size per section may index
relative abundance within limits.' Grayling less than 300 mm in fork
length comprised the lower river catch through section 4. The size distri-
bution in Sections 5 through 12 consists of larger fish in the 200 -400 mm
fork length range. Main river Sections 13 and 14, plus 15 through 17 of
the right fork, contained by far the highest percentage of large grayling.
23
[
Table 12. Age Composition and Observed Length-Age Relationships of 75 Arctic [
Grayling Electrofished in the Richardson Clearwater River, 1973.
Fork Length [
(mm) I II III IV v VI VII VIII IX X XI+
[
90-91 1
110-119 1 [
120-139
140-159 1 r
160-179 1 r·
180-199
200-219 3
r,
L
220-239 6 1 1
240-259 2 6 2 [
260-279 1 7 4 [
7 9 280-299
300-319 1 8 2 [
320-339 2 3 1
340-359 1 1 L
360-379 1 1 [
380-399
400-419 1 [
420-439
No. of Fish 3 0 13 22 26 8 2 0 0 1 r
L
Age Comp. 4.0 0 17.3 29.3 34.7 10.7 7.0 0 0 1.3 l (%)
Avg. Length 121 0 226 271 295 321 348 0 0 412
(mm) [
S.D. 33 0 25 20 23 42 44
L
24
L
I ,, l j L I : J " ' i J
Table 14 Back-Calculated Length (mm) at Each Year of Life of 61 Arctic Grayling, Richardson Clearwater
River, 1973.
Age At
Capture n Ll L2 L3 L4 L5. L6 L7 L8 L9 L1o Ln+
I 3 100
II 1 91 153
III 12 92 141 201
IV 20 88 148 198 240
v 19 93 139 190 229 263
N VI 5 93 143 186 226 259 287 0\
VII 1 118 183 234 287 317 332 355
VIII
IX 1 86 135 180 237 276 306 331 367 385
X
XI
Weighted Mean 93 146 199 235 265 296 343 367 . 385
Length
Mean Annual 93 53 53 36 30 31 47 24 18
Growth Increments
~
I ;
,.._...,
' J
DELTA CLEARWATER, 1973
RICHAROSON CLEARWATER,I973
-e
E -
i. 0~----~--~--r-~--~--~~---.--~-.--~
0 I II .11[
r~ N3E CLASS
FIGURE 8. Back Calculated Fork Lengths, Increments, Grayling, Delta
Clearwater and Richardson Clearwater Rivers, 1973.
-c -:I:
t-
(!) z
LaJ
...J
::::.::
0:::
0
LL.
Table 15. Percent Occurrence by Fork
June 20 to July 5, 1973.
Fork
Length (mm) 1 2 3 4 5
50-99
100-149 25 100 17
150-199 25
200-249 49
250-299 50 100 17
N 300-349 17 00
350-399
400-449
Sample Size 4 2 2 6
*Right Fork
Length For Arctic Grayling Sampled
6 7 8
17
56 66 56
24 34 17
15
7 6 6
I~
River
9
20
60
20
5
Section
10
11
56
22
11
9
r-....,
' ' J
11
17
58
25
12
in the Delta Clearwater River,
12 13 14 15* 16* 17*
2
6
14 2
20 23 10 8 2
20 34 42 35 42 so
60 20 38 47 47 43
3 10 6 11 5
5 35 21 51 19 65
~
' 1
These data on distribution were also confirmed by both visual and angler
contact methods.
Sex Compositions:
Of 57 grayling autopsied from the Delta Clearwater River, males comprised
44%, and females 56%, of the sample. The small sample size prevents any direct
analysis of composition by age group.
Data collected for maturity analysis yielded unclear results. This was due
to the small sample size and the fact that there is little evidence to
indicate many mature grayling spawn in these systems.
Spawning Locations and Timing:
Data collected to date fails to indicate a major spring spawning run of
Arctic grayling into the Delta Clearwater River. No ripe pre-spawning
adults were captured during the 1972 -1973 field season. A check of spring
angler catch also failed to turn up any pre-spawners. However, in sampling
a spring area in Section 6 on 7/25/73 with a back-pack DC shocker, nine
young-of-the-year grayling were captured. Their mean length was 62 mm,
with a range of 54 -68 rnrn. Rearing silver salmon were also captured
in this spring.
Grayling that had recently spawned were captured as early as mid-May, with
the influx of larger, mature grayling completed by mid-June.
Obviously, some grayling do indeed successfully spawn in the Delta Clearwater
River. However, no other rearing grayling were captured in all the areas
sampled.
Round Whitefish Life History
Interstream Migration:
A summary of round whitefish tagged and recaptured in 1973 is shown in
Table 16. Of 657 tagged in Section 80 (Figure 1), three (0.4%) moved
upstream to the Delta Clearwater, and two (0.3%) were later recaptured
downstream in the Richardson Clearwater River. This suggests both small
up and downstream summer dispersions. Two were caught by anglers in the
tagging area during the summer. Of the 904 tagged in section 81, 53 (6%)
were later recaptured irnrnedi~tely upstream in the Delta Clearwater, while
only 1 (0.1%) was recaptured downstream in the Richardson Clearwater. Round
whitefish tagged in Sections 80 and 81 probably overwinter in these areas of
the Tanana River.
29
TABLE 16. Tagging Summar.y of Round Whitefish in the Tanana Drainage, 1973.
Round Whitefish Tagging
Location
Tanana River
Section 80
Section 81
Delta Clearwater River
Round Whitefish RP.captured
Location Tagged
Tanana River
Section ~0
Section 80
Section 80
Section 81
Section 81
Section 81
Delta Clearwater River
Dates Number Tagged
3/27-3/30
3/30-4/1
4/10-5/18
657
904
1,086
Total 2,647
Location Recaptured Number (%)
Delta Clea~watPr River 3 (0.4)
Richardson Clearwater River 2 (0.3)
Section 80 2 (0 .. 3)
7 (1. 0)
Delta Clearwater River 53 (6. 0)
Richardson Clearwater River 1 (0.1)
Clearwater Lake 1 (0. 1)
55 (6. 0)
D.elta Clearwater River 123 (11. 0)
Total 185 (7.0)
30
[
r-
L
[
r~
L:
[
[
[
[
[
[
r
L
L
[
L
[
Intrastream Migration:
In 1973, 1,086 round whitefish were tagged in the Delta Clearwater River.
Of these, 123 (11%) were later recaptured in the same stream. General
movement trends are depicted in Figure 9. The majority of fish tagged in
March and April showed a tendency for upstream migration when later re-
captured. This agrees with visual observations. Those whitefish tagged
in May showed mixed tendencies, with more downstream displacement than before.
This also agrees with observations, as many whitefish (excluded by the
week restriction) were recaptured a considerable distance downstream within
a few days following tagging operations. Handling rather than normal
migration is believed to have caused the displacement.
Abundance:
Table 17 presents estimates of round whitefish abundance in the Delta
Clearwater River. As with grayling, the Schumacher-Eschmeyer estimate gives
closer confidence limits. It can be seen that round whitefish outnumber
grayling by six to one.
TABLE 17. Estimates of Round Whitefish Abundance in the Delta Clearwater
River, 1973.
Sample River Schnabel 95% RWF Per Schmacher-95% RWF
Dates Section Estimate CI mi. km. Eschmeyer CI mi
mi km Estimate
Per
km
7/3 17 2 13,664 10,391 854 547 13' 611 10,923 851 544
8/15 27 3 21,819 18,056
Abundance estimates of round whitefish in Sections 80 and 81 of the Tanana
River are shown in Table 18. The number of whitefish (14,662) in Section
81 is close to that in the Delta Clearwater River (13,611) just upstream.
Based on these data and tagged fish recaptures, it is probable that white-
fish in Section 81 move up to the Delta Clearwater River and Clearwater Lake
in the summer to feed.
Length Frequency:
Round whitefish length frequencies are displayed in Figure 10. The distri-
bution of whitefish in the Delta Clearwater River appears normal, with a mean
at 359 mm.
31
m MONTH TA6GED
I..L. 10 ~ June
ffi 5.
CD
~
~ 15
I..L.
~ 10
a::: w
~ 5
:::::> z
25
ffi 20
I..L.
~ 15
ffi
CD
::E 10 ~
5
20
:I:
!!.?
I..L. 15
~
§;j 10
::2:
:::::> z
5
May
April
n -- -
March
r-
.!'!. - -UP ON NM UPoN NM
APRIL MARCH
• • •
r-
n - -.
r
n . . -. --. . --- -
r--
r
ll n n~ n . . . . . . . . . . -.
r-
• • • --------- -
r-
_0 . "" . LPDNNM ----. UP ON NM .. ----UP Q\J NM UP ON NM
JUNE JULY AUGUST SEPTEMBER
MONTH RECAPTURED
Figure 9. The R0stricted* Number of Round Whitefish Recaptured
that Moved Up (Up), Down (DN), or Showed No Movement
(NM) in the Delta Clearwater River, 1973.
*Excludes recaptures within a week of prev.ious capture.
32
-
[
.r·
[
[
r·
L
L
[
[
[
[
[
·r
L
[
[
L
[
--~
~.
---'
~
..c
1/1
LL -0
...
l Cll
~
·-' ~ z
-~
Tanana River -Section 80
40 -3127 -3130173
n= 286
I• 30 i= 300 mm ........
.........
.................
1--,....... 1--
20
1--1--
r--1--1--
l___r-fl r--r--
rfl-l n ~
10
0
Tanana River-Section 81
3 I 30 - 4 I I I 7 3
40 n = 296
'i= 350 mm _ ........
30 .....-~----
1--I--
20 ,.......
.--
.ILJ nr--rr--11 h -
10
0
Delta Clearwater River
Summer D istributlon
40 n= 272
x=359 mm ...--...--...--
30
~
1---.........
20 -
1--
10 ......... r-
_.-n ..r HI
Fork Length (mm)
FIGURE 10. LENGTH FREQUENCIES OF ELECTRO-FISHED
ROUND WHITEFISH FROM NEARBY LOCALES
IN THE TANANA RIVER WATERSHED, 1973.
10
5
0
15
10-c ....
0
t-
5 -0
....
c:
0 Cll
u ...
Cll a..
15
10
5
TABLE 18. Estimates of Round Whitefish Abundance in Sections 80 and 81 of the Tanana River, 1973.
Sample River Section Schnabel 95% RWF Per Schumacher-95% RWF Per
Dates mi km Estimate CI mi km Eschmeyer CI mi km
Estimate
Section 80
3/27-30 2 3.2 3,924 3,004-6,147 1,962 1,226 3,378 2,271-6,589 1,689 1,056
Section 81
3/30 4 6 14,296 9,814-34,179 3,574 2,383 14,662 12,604-17,410 3,666 2,444
VI
.j:::..
--
r-~
I
r--"""
I
L_o
[
L
L
L
The distribution for round whitefish captured below the Delta Clearwater River
in Section 81 of the Tanana River follows a similiar trend, with a mean fork
length of 350 mm, further indicating that some of these fish probably migrate
to feed in the Delta Clearwater system during the summer.
Smaller size classes are represented more frequently in the sample taken in
Section 80. There are fewer with a fork length above 340 mm, than in Section
81 or the Delta Clearwater River. The possibility that round whitefish are
distributed by size, with smaller fish further downstream in the Tanana River
between Sections 80 and 81, is quite good.
Length -Weight Relationship:
The length-weight relationship for round whitefish in the Delta Clearwater
River (Figure 11) shows a trend for weight of fish below 350 mm fork length
to increase with time. At lengths greater than 350 mm, weights initially
increased then decreased. A possible explanation is that the larger, mature
round whitefish tend to reduce feeding as August approaches. Stomachs
of larger fish collected in August were markedly emptier than those collected
in May.
Condition Factors:
Round whitefish condition factors (Table 19) increased with size in the
April and May samples, and decreased with size in the July sample. Those
fish large enough to spawn would have done so the preceding fall. As
opposed to grayling, there was time for a subsequent weight gain during
the winter. A possible explanation for a reduction in weight at a given
length and therefore a lower K factor in the July sample was the feeding
slowdown mentioned above.
TABLE 19. Relative Condition Factors (K = W/FL 3 x 105) For Round Whitefish
Sampled in the Delta Clearwater River, 1973.
Length Group Sam:ele Period
(mm) 4/11-16 5/14-16 7/03-06
190-209 0.851 0.967 1.445
210-229 0.899 0.988 1. 377
230-249 0.921 1.007 1. 318
250-269 0.939 1. 024 1. 265.
270-289 0.957 1.042 1. 218
290-309 0.975 1. 059 1.177
35
TABLE 19. (cont.) Relative Condition Factors (K = W/FL3 x 105) For Round
Whitefish Sampled in the Delta Clearwater River, 1973.
Length Group
(mm)
310-329
330-349
350-369
370-389
390-409
410-429
430-449
450-459
4/11-16
0.990
1.005
1. 019
1.033
1. 047
1.060
1.072
1. 080
Age Composition and Lengths at Age:
Sample Period
5/14-16
1. 074
1. 088
1. 102
1.115
1.129
1.141
1.153
1.-161
7/03-06
1. 139
1.104
1.072
1.044
1. 016
0.992
0.968
0.952
The age composition and length relationship for 120 round whitefish captured
in the Delta Clearwater River is shown in Table 20. Age V through VIII
fish comprise the bulk of the sample. Fish younger than age V and older
than age IX are fewer in number. Determining age of round whitefish
scales above age VIII becomes increasingly difficult, as annuli tend to
be separated by only two or three circuli. Hence, all fish of age XI
and older are grouped. The oldest round whitefish captured was at least
age XVI.
TABLE 20. Age Composition and Observed Length-Age Relationships of 125
Round Whitefish Electrofished in the Delta Clearwater River,
1973.
Fork Length
(mm)
180-199
200-219
I II III
2
IV v VI VII VIII IX X
36
XI
[
[
[
r~
L
[
[
[
r l J
r
[
[
[
r·
L
[
L
[
L
I ,
I
[
[
[
[
r
L
L
L
L
L
5114-16173, W=2.959x I0-6 (FL'3.223) N=60
EK>O 7/03-oG/73, W=2.118xi0-4(FL2.493) N=42
700
300
200
100
0
ligill'l' ]].
100 200 300 400 500
F~K LENGTH (MM)
Length l\<·igh1 l~clntionship of i{otwJ Whitefish (Sexc';
Crot!Jil'<il !'t·om the llclta Clearwater l~ivcr, 1973.
37
[
TABLE 20. (cont.) Age Composition and r
Observed Length-Age Relationships of
125 Round Whitefish Electrofished in the Delta Clearwater r-River, 1973.
l ~
----·---· [ Fork Length
(mm) I II Ill IV v VI VII VIII rx X XI
220-239 1 2
[
240-259 1 2 1 1 [
260-279 7 2
280-299 8 9 2 r~
300-319 6 6 2 ,-
320-339 5 12 4 l
340-359 1 15 3 1 1 [
360-379 1 5 5 2 '") 1
.l L .l
380-399 1 2 [
400-419 1 3 r 420-439 1 1
440-459 2 1 [
No. of Fish 0 0 4 4 16 25 41 16 8 5 6
Age Camp. 0 0 3.3 3.3 13.3 20.8 33.3 15.0 5.8 5.0 0 r-
(%)
Mean Length 0 0 215 242 275 306 336 357 389 395 0 [
(mm)
S.D. 0 0 24 10 15 27 21 31 4'7 39 0 r
L
------
/ Back-Calculated Lengths:
[
Back-calculated lengths and growth increments for round whitefish 1n the [
Delta Clearwater system are shown in Table 21. Growth rates decrease with
age particularly after age IV. The calculated lengths approximate empirical
L data presented in Table 20.
38
[
[
[
[
[
[
[
[
[
[
[
Length Distribution:
Round whitefish distribution by length (Table 21) in the Delta Clearwater
River followed a pattern similar to that of grayling. Again, smaller fish
(less than 300 mm) predominated the lower stream sections. However,
fish greater than 300 mm in fork length were captured throughout the system.
Only in Sections 15 through 20 of the right fork were fish less than 300
mm fork length absent in the sample.
Sex Composition:
Analysis of data collected from 128 autopsied
comprised 46% and females 54% of the sample.
to age IX, after which females predominated.
Maturity:
round whitefish showed males
Sex ratios were balanced up
Fifty-three round whitefish of ages V, VI, and VII from the Delta Clearwater
River were examined for maturity. All age V fish were immature. Sixty-six
percent of both males and females of age VI were mature, as were all fish
age VII and older. Seventy percent of female round whitefish between 290-
309 mm and all larger females were mature. Seventy percent of male round
whitefish between 290 -329 mm and all larger males were mature.
The data collected indicates that round whitefish are consecutive spawners
as all age VII and older fish sampled showed a development of reproductive
products for fall spawning.
During the experimental silver salmon egg take (10/10-11/73), 11 round
whitefish larger than 333 mm in fork length were autopsied. Seven were
females that had recently spawned, one female was still ripe, and three
males captured had also just spawned.
During peak silver salmon spawning counts (10/17-23/73), fewer than 1,000
round whitefish were observed in the Delta Clearwater River.
Egg Counts:
Limited samples of round whitefish were collected for egg count determinations
in the Richardson and Delta Clearwater rivers. A subsample of four fish taken
on August 1 from the Richardson Clearwater River showed a mean of 12,529
eggs per female with a range from 9,145 -17,010. Egg diameters averaged
1.9 mm with a range of 1.8-2.0 mm.
A single female taken October 11 from the Delta Clearwater River contained
6,200 eggs with a mean egg diameter of 2.8 mm. This single ripe female
was captured in Section 10 along with seven other females that had recently
spawned.
39
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0
TABLE 21. Back-Calculated Length (mm) At Each Year of Life of 64 Round Whitefish, Delta Clearwater
River, 1973.
Age At
Capture n Ll L2 L3 L4 Ls L6 L7 La L~ LlO Lll+
I 0
II 0
III 2 97 155 195
IV 4 80 156 202 242
v 5 85 147 197 240 279
VI 9 78 150 193 238 271 297
VII 19 80 138 190 237 272-299 322
VIII 9 80 136 187 236 270 301 335 341
IX 5 88 147 190 235 264 296 326 348 373
X 4 77 121 168 209 247 275 305 323 351 371
XI+ 7 77 131 175 213 251 283 311 336 355 368 395
64
Weighted Mean 81 141 188 233 267 295 322 338 360 369 395
Length (mm)
Mean Annual (mm) 81 60 47 45 34 28 27 16 22 9 26
Growth Increments
I -.•
.j:>.
~
C~1 L r-' t' ' )
r ---,
c J
:·-;
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j
TABLE 22. Percent Occurrence by Fork Length for Round Whitefish Sampled in the Delta Clearwater
River, 1973.
Sample Fork River Section
Dates Length (mm) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15* 16* 17* 18*
5/14-5/18 50-99
100-149
150-199
200-249 8 10 3 3 2 15 2 3 2
250-299 25 10 10 13 9 16 13 6 7 3
300-349 42 52 40 37 50 35 25 34 25 27 7 34 50 52 19 21
350-399 25 28 40 37 35 38 49 23 40 so 50 79 51 30 41 54 47
400-449 7 10 6 9 13 23 18 25 13 14 10 20 7 27 32
Sample Size 12 21 30 30 32 43 24 13 50 12 30 14 59 20 27 48 19
*Right Fork
19* 20*
10
38 52
62 38
8 21
The possibility that round whitefish spawn in the Delta Clearwater River,
although slim, still exists. No rearing round whitefish were captured.
The smallest fish captured was 191 rnrn fork length and age III. On August
30, numerous ripe round whitefish were captured in Section 81 of the Tanana
River. By early September visual observations showed a comparative absence
of round whitefish in the Delta Clearwater River. On a trip to the Good-
paster River on the 17th, 18th, and 19th·of September, 1973, concentrations
of pre-spawning round whitefish were observed 50 -60 miles upstream. Two
round whitefish tagged in the Delta Clearwater River were seen in a large
school.
Food Habits:
Aquatic invertebrates were collected throughout the Delta Clearwater River
system and a faunal list is shown as Table 23.
TABLE 23. Delta Clearwater Faunal List (tentative)
Turbellaria (Flatworm)
Oligochaeta (Segmented worms)
Acarina (Water mites)
Arnphipoda (Gammarus sp.)
Insecta
Emphemeroptera
Baetidae
Baetis bicaudatus
Heptageniidae
Cinygmula sp.
Emphemerell idae
Ephemerella (Drunella) doddsi Needham
Plecoptera
Nemouridae
Nemoura sp.
Capnia sp.
Chloroperlidae
Alloperla sp.
Perlodidae
Isoperla sp.
Hemiptera
Corixidae
Trichoptera
Rhyacophilidae
Rhyacophila sp.
Limnephilidae
Discosmoecus sp.
Pycnopsyche sp.
Caborius sp.?
Diptera
Tipulidae
Dicranota sp.
42
(species to be determined)
(species to be determined)
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TABLE 23. (cont.) Delta Clearwater Faunal List (tentative)
Chironomidae (Genera to be determined)
Tanypodinae
Diamesinae
Diamesa sp. A.
Diamesa sp. B.
Orthocladiinae
Orthocladius sp.
Simuliidae
Prosimulium sp.
Stephen L. Elliott of the Alaska Department of Fish and Game, Sport Fish
Division, Juneau identified the invertebrates and compiled the faunal list.
A Provisional Key to the Aquatic Invertebrates of Delta Clearwater River
is on file in the Fairbank$ office.
Table 24 presents a limited picture of food preferences versus availability
based on two benthic and two stom,ach samples. Both grayling and round
whitefish prefer and possibly compete for the same food items.
TABLE 24. Some Food Preferences of Round Whitefish and Arctic Grayling,
Delta Clearwater River, July 5, 1973.
Stomach Samples (2)
Benthic Samples (2) Grayling Whitefish
Faunal List n % n % n %
Turbellaria 3 3
Oligochaeta 13 8
Acarina 1 0.05
Arnphipoda
Gammarus sp.
Ephemeroptera
Batidae 37 23 1,092 57 703 72
Heptageniidae 58 35 273 14 228 23
Ephemerellidae 1 0.1
Plecoptera
Nemouridae 3 2 3 0.2
43
.•
TABLE 24. (cont.) Some Food Preferences of Round Whitefish and Arctic
Grayling, Delta Clearwater River, July 5, 1973.
Stomach Samples (2)
Benthic Samples (2) Grayling Whitefish.
Faunal List n % n % n
Chloroperlidae 3 2 2 0. 1 3
Perlodidae 20 1 1
Hemiptera
Corixidae
Trichoptera
Rhyacophilidae
Limnephilidae 203 10.5 15
Diptera
Tipulidae
Chironomidae 23 14 326 17 24
Simuliidae 1 1 5 0.2
Exuviae 20 12
Silver Salmon Life History
The silver salmon investigations in the study area consisted of spawning
and outmigrant enumeration, an experimental egg take, and rearing fish
sampling. Life history data are presented here.
Two smolt or outmigrant traps were fished continuously from May 25 until
June 27 in Section 2 of the Deita Clearwater River. A total of 16 silver
salmon was captured, with a fork length range of 78 -101 mm. Weights
ranged from 4.9 -10.6 mm. These fish were age II. However, their size
and capture rate indicate the majority of larger smolt had outmigrated
prior to establishing traps. Silver salmon smolts were captured while
marking round whitefish in Section 80 of the Tanana River the week in
March.
9,: . 0
0.3
0. 1
2
2.5
A sample of 24 fry from a spring area in Section 2 showed that they had
obtained a mean length of 37 mm and a weight of 0.5 gm by June 14. Another
44
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sample taken
salmon had a
age I fish.
length of 35
from a spring area in Section 6 on July 25 showed that 15 age I
mean fork length of 71 mm. Weights averaged 4.8 gm for these
Fourteen age 0 salmon were also captured and had a mean fork
mm. Weights ranged from 0.4-0.7 gm.
It appears that the size composition of thes~ rearing silver salmon is
dependent on time of hatching and rearing habitat conditions, i.e., those
salmon hatching earlier and occupying ideal rearing areas tend to be
larger than those that do not.
Young-of-the-year and age I silver salmon were observed and captured along
the stream margins in cover areas during the summer. Some were also cap-
tured in spring areas. Fall sampling showed an almost total absence of
these rearing fish along the stream margins. They were, however, captured
in spring areas in greater numbers than during the summer. The springs
tend to maintain higher temperature than the main river throughout the year,
and are the preferred overwintering habitat.
Age analysis of 58 adult silver salmon captured in September and October
showed all fish sampled to be age 2.1. The mean mid-eye to fork length
for males was 560 mm. The mid-eye to fork length multiplied by 1.15 gave
the estimated fork length for males. Females weighed an average of 3.4 kg
and males averaged 2.9 kg prior to spawning.
Escapement Counts:
In 1973, pre-spawning silver salmon were first observed on September 24 in
the Delta Clearwater River. Peak spawning occurred around mid-October and
salmon were still present on November 27.
Table 25 summarizes minimum silver salmon escapements in the Delta Clear-
water River during 1972 and 1973. The estimated number in 1972 (632) is
equal to 19% of those counted in 1973 (3,322). However, the counts in
1972 were made at a later date under poorer conditions. The counts in 1973
were made under peak spawning conditions from an elevated platform mounted
on a riverboat, which gave excellent results. Individual fish were easily
counted in the clear water.
The relative number of spawners by stream section was similar during both
survey years. River Sections 2 of the main river, plus 15 and 16 of the
right fork were preferred. Spawning density in 1973 per unit surface area
was 25 per hectare or 10 per acre surveyed. No attempts were made to survey
salmon abov~ section 18 in the right fork or in any section of the left
fork due to impassable conditions for riverboats. The salmon utilize
these areas, but to a lesser degree.
An estimated 551 silver salmon spawned in the outlet of Clearwater Lake
during the fall of 1973. Young salmon utilize Clearwater Lake as a rearing
area. Approximately 350 to 400 silver salmon were also observed in the
Richardson Clearwater River.
45
TABLE 25. Minimum Estimated Silver Salmon Escapements in the Delta
Clearwater, 1972 and 1973.
River Salmon Counts
Section 11/9/72 10/17-24/73
1 22 132
2 73 532
3 23 43
4 52 227
5 69 151
6 48 79
7 19 22
8 22 222
9 17 52
10 31 154
11 5 170
12 13 131
13 13 215
14 15 217
15* 144 387
16* 26 364
17* 218
18* 6
Totals 632 3,322 ""
*Right Fork
Over 1,000 churn salmon utilized Mile 1 Slough as a spawning area during
the fall of 1973. They entered around the middle of September and peak
spawning occurred shortly thereafter. Approximately 40 churn salmon utilized
Section 1 and 2 of the Delta Clearwater River for spawning. Four churn salmon
were observed in the Richardson Clearwater River with the silver salmon.
46
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--_,
Experimental Egg Take -Egg Counts:
An experimental egg take for silver salmon was conducted on October 10 and 11,
1973 in the Delta Clearwater River. Sixty-five females and 32 males wer
captured by electroshocker boat. Approximately 15 females were green. The
egg yield, as estimated by the Fire Lake Hatchery in Anchorage, was 173,700
an average of 3,474 eggs per female, for SO females. Egg count determinations
from ovaries preserved by freezing 4,367 per female, with a range of
3,865 -5,082 eggs per female; egg diameter averaged 5.5 mm.
Creel Census
The results of non-statistically based angler interviews are summarized
in Table 26. Of 315 anglers contacted, total censused effort was 664
angler hours, yielding 436 grayling (0.65 fish per hour). The average
catch size was 302 mm (11.9 in.).
TABLE 26. Censused Angler Catch and Effort in the Delta Clearwater
River, 1973.
Month
May
June
July
August
Totals
No. of
Anglers
Contacted
147
104
51
13
315
Anglers*
Hours
253
246
137
28
664
Angler
Catch
203
158
49
26
435
*Includes only data from Anglers who responded.
Catch Per**
Hour
0.78
0.64
0.36
0.93
-
X 0.65 X
**Includes only data when both catch and effort were given.
-
X
Fork Length
(mm)
Range
290 180-370
336 220-440
282 210-390
301 250-380
302 180-440
The total censused catch (436), if added to the population estimate of
2,267, would equal a 16% angler catch, barring any outmigration or
natural mortality. Few anglers censused caught their limits.
Table 27 presents a comparison of censused catch and effort for the years
1953 -1958 and 1973. The censused catch was higher in 1973 than any pre-
viously determined. However, the 12 inch minimum size limit in effect
from 1955 -1958 prevented the legal catch of younger, smaller, yet avail-
able grayling.
TABLE 27. Comparison of Censused Catch From the Delta Clearwater River, 1953
to 1973.
Year Anglers Contacted Angler Hours Catch Catch/Hour
1953 300 1, 057 307 0.29
1954 48 113 52 0.46
1955* 52 172 126 0.73
1956* 172 680 211 0.31
1957* 102 514 211 0.41
1958* 115 835 259 0.31
1973 315 664 436 0.65
*12 inch size limit ~n effect from 1955 through 1958.
48
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LITERATURE CITED
Reed, R. J. Life History and Migration Patterns of Arctic Grayling, Thymallus
arcticus, (Pallas), in the Tanana River Drainage of Alaska. Alaska Depart-
ment of Fish and Game. Research Report No. 2. 30 pp.
Ricker, W. E. 1958. Handbook of computations for biological statistics
of fish populations. Bull. Fish. Re~. Bd. Can. No. 119, pp. 81-110.
Roguski, E. A. and P. C. Winslow. 1969. Investigations of the Tanana River
and Tangle Lake Grayling Fisheries: Migratory and Population Study.
Alaska Department of Fish and Game. Federal Aid in Fish Restoration,
Annual Report of Progress, 1968-1969, Project F-9-1, 10: 333-351.
Schallock, E. W. and E. A. Roguski. 1967. Investigations of the Tanana
River and Tangle Lakes Fisheries: Migratory and Population Study.
Alaska Department of Fish and Game. Federal Aid in Fish Restoration,
Annual Report of Progress, 1966-1967, Project F-5-R-8, 8: 247-255.
Tack, S. L. 1971 .. Distribution, Abundance, and Natural History of the
Arctic Grayling in the Tanana River Drainage. Alaska Department of
Fish and Game. Federal Aid in Fish Restoration, Annual Report of
Progress, 1970-1971, Project F-9-3, 12: p.22.
Van Huile, F. D. 1968. Investigation of the Fish Populations in the Chena
River. Alaska Department of Fish and Game. Federal Aid in Fish Restoration,
Annual Report of Progress, 1967-1968, Project F-5-R-9, 9: 287-304.
Prepared By:
Gary A. Pearse
Fishery Biologist
49
Approved By:
s/Howard E. Metsker
Chief, Sport Fish Research
s/Rupert E. Andrews, Director
Division of Sport Fish