Abundance, egg production, and age-sex-size composition of the chinook salmon escapement in the Chena River, 1990, MJ Evenson

Tags: chinook salmon, Chena River, sampling events, Alaska Department of Fish and Game, abundance, sampling event, egg production, Federal Aid, size, Total, estimate, composition, Alaska, harvest estimates, sampling effort, accurate estimate, Alaska Department of Fish and Game, Division of Commercial Fisheries, PP, Anchorage, Fishery Data Series, Alaska Department, estimation of animal abundance, sampling bias, Salcha River, point estimate
Content: Fishery Data Series No. 92-4 Abundance, EGG PRODUCTION, and Age-Sex-Size Composition of the Chinook Salmon Escapement in the Chena River, 1991 bY Matthew J. Evenson
March 1992
Division of Sport Fish
FISHERY DATA SERIES NO. 92-4 ABUNDANCE, EGG PRODUCTION, AND AGE-SEX-SIZE COMPOSITION OF THE CHINOOK SALMONESCAPEMENT IN THE CHENA RIVER, 19911 BY Matthew J. Evenson
Alaska Department of Fish and Game Division of Sport Fish Anchorage, Alaska March 1992
l This investigation
Restoration
Act
S-3-l(a).
was partially
financed by the Federal Aid in Sport Fish
(16 U.S.C. 777-777K) under Project F-10-7, Job No.
The Fishery Data Series was established in 1987 for the publication
of
technically oriented results for a single project or group of closely related
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Fishery Data Series reports are intended for fishery and other
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Distribution
is to state and local publication
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TABLE OF CONTENTS LIST OF TABLES ............................................... LIST OF FIGURES.............................................. LIST OF APPENDICES........................................... ABSTRACT..................................................... INTRODUCTION................................................. MATERIALS AND METHODS........................................ Capture and Marking ..................................... Recovery ................................................ Abundance Estimator ..................................... Tag Loss ................................................ Age, Length, and Sex Compositions ....................... Potential Egg Production ................................ Aerial Survey ........................................... Goodpaster and Chatanika Rivers ......................... RESULTS...................................................... Tests of Assumptions for a Petersen Estimator ........... Sex and Size Selectivity ........................... Closed Population .................................. Abundance Estimate ...................................... Tag Loss ................................................ Age, Length, and Sex Compositions ....................... Potential Egg Production ................................ Aerial Survey ........................................... Goodpaster and Chatanika Rivers ......................... DISCUSSION ................................................... -i-
Pape iii iv V 1 2 4 4 4 4 8 8 9 10 11 11 11 11 11 11 15 15 15 15 21 21
TABLE OF CONTENTS(Continued) ACKNOWLEDGEMEN..T...S........................................ LITERATURE CITED ............................................. APPENDIX A ................................................... APPENDIX B ................................................... APPENDIX C...................................................
Page 23 23 27 32 35
-ii-
LIST OF TABLES
Table
1. Harvests of anadromous chinook salmon by sport, commercial, subsistence, and personal use fisheries, Tanana River drainage, 1978-lggl.......................
2. Description of equipment and control settings used while electrofishing...................................
3. Number of male and female chinook salmon marked
while electrofishing
that were recovered and not
recovered during carcass sampling......................
4. Capture and recapture history of all chinook salmon sampled during the mark-recapture experiment...........
5. Estimates of proportions and abundance of female and male chinook salmon by age class collected during carcass sampling, Chena River, 1991 . . . . . . . . . . . .
6. Estimated length-at-age of Chena River chinook salmon, 1991...................................................
7. Estimated potential egg production of Chena River chinook salmon by length category, lggl................
8. Estimated abundance, maximum aerial counts, and survey conditions for chinook salmon in the Chena River, 1986-lggl.......................................
Page 3 5 12 14 17 18 19 20
-iii-
LIST OF FIGURES
Figure
1. Chena River study area.................................
2. Cumulative length frequency distributions
comparing
lengths of all chinook salmon captured during the
marking event to: A) lengths of all recaptured chinook
salmon; and, B) lengths of all chinook salmon captured
during the recapture event.............................
3. Frequency of 500 estimates of abundance using bootstrap
procedures on the capture histories of all chinook
salmon captured during the mark-recapture experiment
using an unstratified
estimator (top panel) and a
stratified
estimator (bottom panel)....................
Page 6 13 16
-iv-
LIST OF APPENDICES
ADDendix
Al. Statistical
tests for analyzing data from a mark-
recapture experiment for gear bias, and for
evaluating the assumptions of a two-event mark-
recapture experiment...................................
Bl. Estimates of the proportions of female and male chinook salmon by age-class, and mean length-at-age estimates from chinook salmon carcasses sampled in the Goodpaster River, lggl.............................
B2. Length compositions of male and female chinook salmon carcasses sampled in the Goodpaster River, 1991...................................................
Cl. Age, length, and sex data collected from chinook salmon carcasses in the Chatanika River, lggl.................
Page 28 33 34 36
ABSTRACT
In 1991, the number of adult chinook salmon Oncorhynchus
tshawytscha
that
returned to spawn in the Chena River near Fairbanks, Alaska, was estimated
using a mark-recapture experiment.
A riverboat equipped with electrofishing
gear was used to capture 612 chinook salmon in late July. Captured chinook
salmon were marked with jaw tags, fin-clipped,
and released. In early August,
389 chinook salmon carcasses were collected.
Seventy-eight of these carcasses
had been marked. The estimate of abundance was 3,025 (standard error = 282)
chinook salmon. The estimates of the number of females and males were 954
(standard error - 99) and 2,071 chinook salmon (standard error - 198),
respectively.
Estimated egg production for the 1991 escapement was 8.5
million eggs (standard error = 600 thousand eggs).
Mean length-at-age
statistics
and age class composition estimates are presented.
During aerial
surveys, the highest count of live and dead chinook salmon was 1,276, or about
42 percent of the mark-recapture point estimate.
KEY WORDS: chinook salmon, Oncorhynchus tshawytscha,
Chena River, abundance,
age-sex-size composition, aerial survey, egg production, tag loss.
-l-
INTRODUCTION
Management of stocks of Yukon River chinook salmon Oncorhynchus tshawytscha is
complex and requires that accurate estimates of escapement be made in a number
of major spawning streams. During a 1,440 km migration from the ocean to
their spawning grounds in the Chena River, chinook salmon pass through five
different sub-districts
of the Yukon River commercial fishery.
Chinook salmon
returning
to the Chena River contribute
to these down river commercial
fisheries as well as to several subsistence and personal use fisheries.
A
sport fishery takes place in the lower 72 km of the Chena River (Table 1).
To perpetuate the fisheries and stocks of chinook salmon, fishery managers set
commercial, subsistence,
personal use, and sport harvest limits on each
fishery with the goal of allowing an adequate number of chinook salmon to
reach their spawning grounds. Harvest levels for the current year are set
based on estimates of the number of chinook salmon that enter the Yukon River
along with results from prior years of the number of chinook salmon that were
harvested, and the number of chinook salmon that reached their spawning
grounds. The sport fisheries in the Chena and Salcha rivers are managed based
on a guideline harvest range. In the Chena River this annual guideline
harvest range is 300 to 600 chinook salmon, while in the Salcha River it is
300 to 700 chinook salmon.
The Chena River has one of the largest chinook salmon escapements in the Yukon
River drainage.
Estimates of abundance and age-sex-size compositions using
mark-recapture techniques have been obtained since 1986 in the Chena River
(Barton 1987a and 1988; Barton and Conrad 1989; Skaugstad 1990a; and Evenson
1991).
The "in-season"
escapements for various spawning stocks have
historically
been determined by aerial counts of chinook salmon on or near the
spawning grounds.
From 1974 to 1990 the highest annual count of chinook
salmon in the Chena River during aerial surveys has ranged from less than 500
to more than 2,500 fish (Barton pers. c0mm.l). However, only a portion of the
population is usually present during a single aerial survey, and the number of
chinook salmon counted is influenced by weather, water level, water clarity,
and overhanging vegetation.
Numbers of mature chinook salmon counted during
aerial surveys of the Chena River from 1986 through 1990 were 22, 20, 59, 44,
and 26% respectively,
of the estimated abundance from mark-recapture
experiments.
In addition to underestimating abundance, aerial surveys do not
provide estimates
of age-sex-size compositions, or potential egg production,
which are needed to better assess the quality of the spawning escapement.
The specific objectives in 1991 were to estimate:
1. the abundance of adult chinook salmon in the Chena River; and,
2. the age-sex-length River.
compositions of chinook salmon in the Chena
1 Barton, Louis. 1990. Personal Communication. Fairbanks, AK 99701
ADF&C, 1300 College Rd.,
-2-
Table 1. Harvests of anadromous chinook salmon by sport, commercial, fisheries, Tanana River drainage, 1978 through 1991.
subsistence,
and personal use
On-Site Sport
Estimated Harvest by User Group
Harvest
Estimatesa
Statewide Survey Estimates of Sport Harvestb
Subsistence
and
Total
Chena Salcha Chena Salcha Chatanika Nenana Other
All
Commercial Personal Use Known
Year River River
River River
River
River Streams Waters HarvestsC
HarvestsC
Harvest
1978 none none 1979 none none
1980 none none 1981 none none
1982 none none
1983 none none
1984 none none
1985 none none
L.2 1986 none 526
1
1987 none 111
1988 567
19
1989 685 123
1990
24 200
1991 none 30ah
23 105
10 476
0 904
;;
719
817
31 808 3; 260 871 212 525 195 244 73 236 375 231 64 291
N.A.f N.A.
2;
none
0
163
none
:
515
37
none
941
13:
none
0
763
none
1:
984
147
none
1,048
78
none
0
338
373
none
75 1,356
0
none
44
781
32:
7
7
474
;:
z;
744
231
963
37
0
0
439
N.A.
N.A.
N.A.
N.A.
635 772 1,947 987 981 911 867 1,142 950 1,202 786d 2,181d 2,989d 1,163ds
1,231 1,333 1,826 2,085 2,443 2,706 3,599 7,375 3,701 4,096 5,58488 2,297=3 3,759es N.A.
2,029 2,620 4,714 3,835 4,408 4,665 4,804 9,873 5,432 5,772 7,090 5,001 7,140s N.A.
Creel census estimates from Clark and Ridder (1987), Baker (1988, 1989), Merritt et al. (1990), and
Hallberg and Bingham (1991).
Sport fishery harvest estimates from Mills (1979-1991).
Commercial, subsistence, and personal use estimates (Schultz, Keith. 1991. Personal Communication.
Alaska Department of Fish and Game, 1300 College Road, Fairbanks, Alaska 99701.
Includes chinook salmon sold from ADF&G test fisheries occurring near Nenana and Manley (24 fish in 1988,
440 fish in 1989, 833 fish in 1990, and 91 fish in 1991).
The personal use designation was implemented in 1988 to account for non-rural fishermen participating
in
this fishery. Harvest by personal use fishermen was 395 fish in 1988 and 495 fish in 1989.
N.A. means data not available at this time.
Preliminary data and subject to change.
Data from Hallberg and Bingham In press.
Potential egg production resulting from the 1991 escapement was estimated, and abundance was compared to aerial counts of spawning chinook salmon. Also included in this report are age-sex-size compositions of chinook salmon sampled during 1991 from the Goodpaster and Chatanika rivers.
MATERIALS AND METHODS
Capture and Marking
Adult chinook salmon were captured from 26 July through 31 July using a
riverboat equipped with electrofishing
gear (Clark 1985; Table 2). The
chinook salmon were stunned using pulsating direct Current Electricity,
dipped
from the river with long handled nets and placed in an aerated holding box.
An area of the river from about river kilometer 72 to river kilometer 145
(measured from the mouth) was sampled in this manner. Past aerial surveys of
the Chena River have shown that almost all chinook salmon spawn in this area
(Skaugstad 1990a). The sample area was divided into three approximately equal
sections (Figure 1). During the first marking event (26, 27, and 28 July),
one pass was made through each section.
Each pass through a section started
at the upstream end of the section and progressed downstream.
Similarly,
during the second marking event (29, 30, and 31 July), one pass was made
through all three sections.
All captured chinook salmon were tagged, fin-clipped,
measured, and released.
A uniquely numbered metal tag was attached to the lower jaw of each fish. A
combination of adipose, pectoral, and pelvic fin clips were used to monitor
tag loss and to identify the location and period of capture of those fish
loosing tags. Length was measured from mid-eye to fork-of-tail
(ME-FK) to the
nearest 5 mm. Sex was determined from observation of body morphology, and
from the presence of stripped eggs or milt.
Recovery
Tags were recovered from chinook salmon carcasses from the same three river
sections in which electrofishing
was performed.
One pass was made through
each section in a drifting riverboat starting at the upstream end of each
section.
Long handled spears were used to collect carcasses.
The carcasses
were measured and examined for fin clips and jaw tags. The sex was determined
from observation of body morphology.
Three scales were removed from each
carcass for age analysis.
Scales were taken from the left side approximately
two rows above the lateral line and along a diagonal line from the posterior
insertion of the dorsal fin to the anterior insertion of the anal fin (Clutter
and Whitesel 1956).
Abundance Estimator
Abundance was estimated separately using two different models. First, an
unstratified
estimate was calculated using procedures described by Chapman
(1951). Tests of the assumptions for use of this estimator (Appendix Al)
indicated that it may have been biased.
Therefore, a stratified
estimate
(Darroch 1961) was also calculated.
The two estimates were then compared for
-4-
Table 2. Description
of equipment and control
electrofishing.
settings
used while
Generator characteristics: WP: Pulse duration: duty cycle: Frequency: Voltage: Amperage: Cathode: Anode:
4,000 KW, 60 Hz, 120 V Coffelt (no model number) Manufactured around 1967. 2.5 milliseconds (ms). 50% 40 pulses per second (pps). 100 - 250 volts (peak). 2 - 4 amperes. The boat served as the cathode. 16 mm (5/8 'I) dia. flexible electrical conduit.
-5-
Middle Fork
Chena River Liule Chcm
Grange Hall Road
10 Kilometers
-Section
Boundary
Figure 1. Chena River study area. -6-
significant
difference using a goodness-of-fit
method described by Seber
(1982). Ultimately,
the unstratified
estimator was chosen as the appropriate
model. Both estimators are described below. The unstratified
model (Chapman
1951) was:
,.
(nl + 1) (n2 + 1)
N-
-1
(1)
Cm2 + 1)
.
(nl+l) (n2+1) (m-m21 (n2-m2>
VW
-
(2)
b2+112b2+2)
where:
N - estimated abundance of chinook salmon;
nl - number of chinook salmon marked during Event 1;
n2 = number of chinook salmon marked during Event 2;
m2 = number of chinook salmon with marks in Event 2; and,
I
I
VW - variance of N.
The stratified
estimator (Darroch 1961) was:
h
E- DuM-lg
(3)
where:
h N = a vector of the estimated each recovery stratum j;
abundance of unmarked chinook salmon in
Du = a diagonal matrix of the number of unmarked chinook salmon carcasses examined for tags in recovery stratum 3.
M = a matrix of nij the number of tagged fish in each recovery stratum j, which were released in tagging stratum i; and,
a- a vector of the number of chinook salmon marked and released in tagging stratum i. I
The total abundance was then estimated as H + the number of marked chinook
salmon. ,.
The variance-covariance LL
matrix of 1 was estimated as follows:
E[(N-N)(N-N)']=DxB-lD,D-l,B'-lDx
+ Dx(D,-I)
(Seber 1982)
(4)
where,
DN - diagonal matrix of estimated abundance in each stratum;
-7-
Dq - diagonal matrix of reciprocals
of pi, which is the estimated
probability
of an animal surviving and being caught;
B - matrix of Bij, the probability
that a member of ai is in stratum j
at sampling and that it is alive; and,
B = D-l,MD,.
Bootstrap procedures (Efron and Gong 1983) were used to estimate sampling bias
for both estimates of abundance. Five hundred bootstrap samples were drawn
randomly from the mark-recapture
histories
of all fish captured in the
experiment.
Each bootstrap sample was randomly drawn with replacement from
all the mark-recapture histories.
An estimate of abundance was calculated for
each bootstrap sample with Equation 1 and 3 giving 500 estimates of abundance
for each model. A measure of the sampling bias for each estimator was the
difference between the point estimate from the original sample and the average
of the bootstrap estimates.
Tag Loss
The proportion of tags lost during the study and the associated variance were estimated using:
I
.pt = n. u/nrL
(5)
V(Pt) - Pt(l-pt>/(n,-1)
(6)
where: . pt = the proportion
of tags lost;
nu - the number of recaptured fish without tags; and,
nr = the total number of fish recaptured.
Ape. Length. and Sex Compositions
Age compositions were calculated from those chinook salmon sampled during the
carcass survey for which scales were collected.
Length and sex compositions
were calculated from all chinook salmon sampled during both events.
The
proportion of females and males by ocean age or length and associated variance
were estimated using: h
Pk = ak/n
(7)
h
h
h
V(Pk) = pk(l-pk)/(n-1)
(8)
-a-
a0 = y intercept (-7,940, from Skaugstad and McCracken 1991);
bo - slope (20, from Skaugstad and McCracken 1991);
MSE, = mean square error from the regression of F on L (2,365,812,
from Skaugstad and McCracken 1991); and,
.
1
V(Fj) = variance of Fj.
Potential egg production h hh E = CN~F~;
of the spawning chinook salmon was estimated
V(i) - D(ta);
and
hh
V(NkFk) = ;k2&)+&&)
-v&&k)
using: (13) (14) (15)
where: h
E
=
A Nk = A Fk =
the production population;
of eggs from the spawning chinook salmon
the estimated number of females of length interval k;
the mean fecundity for females of length interval k as determined by Skaugstad and McCracken (1991) for chinook salmon in the Tanana River drainage;
V(L) = h v(h) = h v(k) -
the variance of the population egg production;
the variance of the mean fecundity and,
for females of length k;
the variance of the estimated number of females of length interval k.
Aerial Survey
Personnel from the Division of Commercial Fisheries of the Alaska Department
of Fish and Game attempted to count the total number of spawning chinook
salmon in the Chena River on four different occasions. High, turbid water and
fog prevented counts on three of these occasions.
A successful count was
conducted 21 July. Counts were made from low flying, fixed-wing aircraft.
Barton (1987b) describes the methods used by the Division of Commercial
Fisheries for aerial surveys.
-lO-
Goodoaster and Chatanika Rivers Chinook salmon carcasses were collected from the Goodpaster River on 16 August, and from the Chatanika River on 13 July and 18 August. Age and sex compositions for chinook salmon collected in the Goodpaster River were estimated using the procedures described above (Equations 7 and 8). Proportions of male and female chinook salmon within 50 mm length categories were calculated in the same manner. Because too few chinook salmon were collected from the Chatanika River, estimates of age-sex-size compositions were not calculated.
RESULTS
A total of 612 chinook salmon were captured, tagged, and released from 26 July to 31 July. During the recapture event, 389 carcasses were collected and examined for tags and fin clips from 6 August to 9 August. Seventy-eight of these fish were marked. Three marked fish had lost tags.
Tests of AssumDtions for a Petersen Estimator
The following results were based on a series of statistical in Appendix Al) conducted with data from the mark-recapture
tests (described experiment.
Sex and Size Selectivity:
No selectivity
in the carcass survey was indicated.
Males and females were
recovered at similar rates (males = 0.12; females - 0.14; x2 = 0.31, df = 1,
0.75 > P > 0.5; Table 3). There was no significant
difference between the
length distribution
of all marked releases and recaptures during the carcass
sample (P = 0.094; Figure 2). The length distribution
of marked fish was not
significantly
different
than the length distribution
of all fish captured
during the carcass survey (P > 0.99; Figure 2). These tests indicate that no
size or sex selectivity
occurred during either sampling event. Lengths and
sexes from both events were combined to estimate length and sex compositions.
Closed Population:
The marked-to-unmarked ratio of chinook salmon was significantly
different
among the three sampling sites during the carcass sampling event (x2 = 12.48,
df - 2, P - 0.002; Table 4). Therefore, all fish did not have an equal
probability
of capture by area during the first sampling event, & marked
fish did not mix completely with unmarked fish between the two sampling
events. Mixing was not complete, but did occur to some extent (Table 4). It
is unknown if marked and unmarked chinook salmon had an equal probability
of
being collected during the second event.
Abundance Estimate
The unstratified
estimate of abundance (Chapman 1951) of all chinook salmon
was 3,025 (SE = 282). The stratified
estimate of abundance (Darroch 1961) of
all chinook salmon was 3,172 (SE = 575). Although there was bias associated
-11-
Table
3. Number of male and female chinook salmon marked while
electrofishing
that were recovered and not recovered during
carcass sampling.
Males
Females
Total
Recovered Not Recovered Total Released Recovery Rate
51 366 417 0.12
27 168 195 0.14
78 534 612 0.13
-12-
0.8
A)
K-S Test: P > 0.09 0.6
0.4 0.2 0 I *,,, 450
I ,,,,I, 550
- - Electrofishing (n = 612)
- Aecapture (n = 78)
11 I. 1 ,, I I1 I I I. I I I I >
650
750
850
950
1050
1-I
0.8 0.6 -
B) K-S Test: P > 0.99
0.4 -
- Electrofishing
0.2 o--/ I I, 450
__.- __- -- -
- - Carcass Sampling
a a I I I a I I I I I I I Ii 1 I1 41 I I. 11 II _
550
650
750
850
950
1050
Length (ME-FK)
Figure 2. Cumulative length frequency distributions
comparing lengths of all
chinook salmon captured during the marking event to: A) lengths of
all recaptured chinook salmon; and, B) lengths of all chinook
salmon capture during the recapture event.
-13-
Table 4. Capture and recapture history of all chinook salmon sampled during the mark-recapture experiment.
River Section Where Marks Were Released Upper Middle Lower Total Unmarked Carcasses Total Carcasses
River Section Where Marks Were Recaptured
Upper Middle Lower Total
19
22
1
42
0
28
4
32
0
0
4
4
19
50
9
78
121
130
60 311
140
180
69 389
Number Marked 260 279 73 612
Number Not Recaptured 218 247 69 534
Total Number of Unique Fish Examined 923
-14-
with the unstratified
estimate, it was not meaningful as there was no
significant
difference between these two estimates (P - 0.409). Because the
unstratified
estimate had a much lower variance, it was selected as the
appropriate estimator.
The bootstrap mean estimates of abundance were 3,060
(SE - 273) for the unstratified
estimate and 4,148 (SE - 983) for the
stratified
estimates (Figure 3). The sampling bias was 35 fish (1%) and 976
(31%) for the two estimates respectively.
Tag Loss
Because all marked fish received both a metal jaw tag and a fin clip, the
proportion of tags lost during the mark recapture experiment could be
estimated.
Seventy-eight marked chinook salmon carcasses were recovered; 75
had tags, and only three had a distinguishable
fin clip and no tag attached.
The estimated proportion of tags lost during the mark-recapture experiment was
0.04 (SE - 0.02).
Age. Length. and Sex Comnositions
Age data were obtained from 339 of the 389 chinook salmon collected during the carcass survey. These fish spent two to five years in the ocean and nearly all fish spent just one year in freshwater (Table 5). The dominant age class for females was 1.4 (brood year 1985), and for males was 1.3 (brood year 1986).
Chinook salmon from both sampling events were used to estimate the proportions
of males and females in the population.
Females comprised 31.9% (SE = 1.5) of
the population, while males comprised 68.5% (SE = 1.5). The estimates of
abundance were 954 female chinook salmon (SE = 99) and 2,071 male chinook
salmon (SE = 198; Table 5).
Lengths of females ranged from 645 to 980 mm, while males ranged from 460 to 1,085 mm. Chinook salmon less than 750 mm were predominantly males. The mean lengths of females were usually greater than the mean lengths of males for a given age (Table 6).
Potential Enn Production
The estimate of total potential 616,000; Table 7).
egg production was 8,532,OOO eggs (SE -
Aerial Survey
Survey conditions were judged to be "poor" on a scale of "poor, fair, and
good".
The count was 1,276 total live and dead chinook salmon on 21 July,
and was conducted just prior to the first marking event. This count was 42%
of the point estimate from the mark-recapture experiment, and was within the
range of observed proportions
from aerial counts conducted since 1986
(Table 8).
-15-
Unstratified Abundance Estimate = 3,025 Mean Abundance Estimate from BooMrap Samples = 3,060 Sampling Bias = 3k (1%)
IIII 24 30 36
IIIIIIIIIIIIIIII 42 48 54 60 66 72 78 84 Abundance (X 100)
50
Stratified 40 Abundance Estimate = 3,172
30
Mean Abundance Estimate
from Boo&trap Samples = 4,148
20 10t 0 24
Sampling Bias = 976 (31%) P trchn v I I I I 1I I I I I 30 36 42 48 54 60 66 72 78 84 Abundance (X 100)
Figure 3. Frequency of 500 estimates of abundance using bootstrap procedures
on the capture histories of all chinook salmon captured during the
mark-recapture
experiment using an unstratified
estimator (top
panel) and a stratified
estimator (bottom panel).
-16-
Table 5. Estimates of proportions and abundance of female and male
chinook salmon by age class collected
during carcass
sampling, Chena River, 1991.
*EF Class Females: 1.3 1.4 1.5 2.4 1.6 2.5 Totals Males: 1.2 1.3 1.4 1.5 Totals
Sample Size Proportion
13
0.038
67
0.198
25
0.074
1
0.003
1
0.003
1
0.003
108
0.315
315*
0.318a
29 113 72 17 231 684a
0.086 0.333 0.212 0.050 0.681 0.685"
Standard Error
Abundance
Standard Error
0.010 0.022 0.014 0.003 0.003 0.003 0.025 0.015a
116
33
598
86
223
48
9
9
9
9
9
9
964
118
9548
99*
0.015 0.026 0.022 0.012 0.025 0.0158
259 1,008 642 152 2,061 2,071*
52 122 90 38 207 198a
Females
and Males:
1.2
29
1.3
126
1.4
139
1.5
42
2.4
1
1.6
1
2.5
1
Totals
339
999*
0.086 0.372 0.410 0.124 0.003 0.003 0.003 1.000 1.000
0.015 0.026 0.027 0.018 0.003 0.003 0.003
259 1,124 1,240 375 9 9 9 3,025 3,025a
52 131 141 64 9 9 9 282 282a
a Based on chinook salmon captured during both sampling events.
-17-
Table 6. Estimated length-at-age of Chena River chinook salmon, 1991.
Ocean AiF Females: 3 4 5 6
Sample Size 13 68 26 1
Total
108
Males:
2
29
3
113
4
72
5
17
Total
231
Females and Males:
2
29
3
126
4
140
5
43
6
1
Total
339
Mean
Length (mm)
SE
Range
738
14
827
6
905
a
980
836
6
645 - 820 740 - 925 830 - 975 980 645 - 980
540
11
726
4
815
7
965
12
749
8
460 - 770 580 - 820 695 - 955 830 - 1,085 460 - 1,085
540
11
728
4
822
5
930
a
980
772 6
460 - 770 580 - 820 695 - 925 830 - 1,085 980 460 - 1,085
-la-
Table 7. Estimated potential egg production of Chena River chinook salmon by length category, 1991.
Length Class (mm>
No. of Females in Sample
Estimated No. of Females in Population
Standard Error
Estimated Egg Standard
Production
Error
(eggs>
640-680
2
6
5
690
1
3
3
700
1
3
3
710
2
6
4
720
0
0
0
730
4
12
6
740
6
18
8
750
8
25
9
760
17
52
14
770
10
31
10
780
20
61
15
790
12
37
11
800
20
61
15
810
20
61
15
820
11
34
11
830
14
43
12
840
22
68
16
850
13
40
12
860
17
52
14
870
13
40
12
880
18
55
14
890
11
34
11
900
15
46
13
910
15
46
13
920
10
31
10
930
8
25
9
940
5
15
7
950
5
15
7
960
7
21
8
970
4
12
6
980
0
0
0
990
2
6
4
1,000
1
3
3
34,641 17,934 18,547 38,319 0 81,543 125,993 172,896 377,826 228,381 469,024 288,771 493,547 505,808 284,938 371,232 596,852 360,655 482,048 376,595 532,475 332,145 462,121 471,317 320,342 261,178 166,302 169,367 241,406 140,398 0 72,651 36,939
25,793 17,934 18,547 28,269 0 45,299 60,175 74,570 131,456 90,362 153,311 106,368 157,532 159,715 105,299 126,587 178,920 124,078 152,174 128,090 163,254 118,289 147,964 150,204 116,736 103,194 79,371 80,726 99,933 73,552 0 52,173 36,939
Totals
314
964
8,532,194
616,207a
a The standard error was calculated as the square root of the sum of the variances of the estimated fecundities for each length.
-19-
Table 8. Estimated abundance, maximum aerial counts, and survey conditions for chinook salmon in the Chena River, 1986-1991.
Estimated
Aerial Survey
Proportion Observed
Year
Abundance
S.E.
Count
Condition
During Aerial Survey
1986 1987 1988 1989 1990 1991
9,065 6,404 3,346a 2,666 5,603 3,025
1,080 563 --249 1,164 575
2,031 1,312 1,966 1,180 1,436 1,276
Fair Fair Fair-Poorb Fair-Goodb Fair-Poorb Poor
0.22 0.20 0.59 0.44 0.26 0.42
a Original estimate was 3,045 (SE = 561) for a portion of the river.
The
estimate was then expanded from distribution
of spawners based upon aerial
counts.
b During these surveys, conditions were judged to vary by area on a scale of
"poor, fair, and good".
-2o-
Goodoaster and Chatanika Rivers
Ninety-three
chinook salmon carcasses were collected from the Goodpaster
River. Sex was determined for 86 of these fish. The proportions of females
and males in this sample was 0.357 (SE = 0.053) and 0.643 (SE - 0.053),
respectively.
The dominant age class was 1.4 (19% of total sample; SE - 4.3)
for females and 1.3 (41.7% of total sample; SE = 5.4) for males (Appendix Bl).
Most of the sample was comprised of fish 650 mm and larger.
Of those fish
smaller than 650 mm, nearly all were males (Appendix B2).
Only eight chinook salmon were collected from the Chatanika River. Four were females, two were males, and two were of unknown sex. Lengths ranged from 693 mm to 930 mm. Age classes 1.3, 1.4, and 1.5 were represented in the sample (Appendix Cl).
DISCUSSION
The success of this annual mark-recapture experiment is heavily dependant on
timing of the sampling events. Ideally, electrofishing
should take place at a
time when virtually
all chinook salmon are in the river, have completed
spawning, and have not yet died.
Carcass sampling should take place
immediately after all chinook salmon have died, but before they begin to
decompose or become covered with silt on the river bottom. If sampling occurs
under these conditions, then achieving equal probabilities
of capture during
both sampling events is most likely.
During the electrofishing
events, most
fish captured had already spawned. Very few carcasses were noticed along the
course of the study area. During the carcass survey only a few carcasses had
decomposed to the extent that sex and length could not be determined.
This
indicated that most fish were not dead for more than a few days. However, a
moderate number of live fish were still in the river during the carcass
sampling, but most all appeared to be in post-spawning condition.
Relatively
few carcasses were sampled compared to previous years (Skaugstad 1990a;
Evenson 1991). This does not necessarily indicate that a large proportion of
the population was still alive.
Adverse weather and water conditions were
more likely reasons for the relatively low number of collected carcasses. The
presence of live fish during carcass sampling does not bias the estimate
unless the marked to unmarked ratio of live fish is different from that of
dead fish. If electrofishing
and handling facilitates
a premature death, then
the marked to unmarked ratio of the carcasses would be greater than that of
the live fish and the estimate would be biased low. To test for this, either
the remaining live fish would need to be sampled, or a separate carcass sample
would need to be conducted at a later date.
In this experiment there was no size or sex selectivity
during either sampling
event, however the ratios of marked to unmarked fish from the carcass survey
varied among river sections.
This indicates that there was incomplete mixing
of marked and unmarked fish among river sections, and there was an unequal
probability
of capture during the first sampling event. An unbiased Chapman
(1951) estimator requires the gear to capture all chinook salmon in the
population with equal probability
during at least one of the sampling events,
or that marked fish mix completely with unmarked fish between sampling events.
-21-
The Darroch (1961) estimate is considered unbiased even though there are
unequal probabilities
of capture. Because the estimates of abundance from the
Chapman and Darroch estimators were similar, the bias due to differing marked
to unmarked ratios among river sections was meaningless in terms of the
estimate of abundance.
Incomplete mixing tends to be inherent with the
present sampling design. Marked fish tend to be recaptured in the section
they were tagged or in sections downstream. When captured for marking, most
chinook salmon had finished or nearly finished spawning and were a few days
from death. Dying fish would be less able to move upstream or maintain a
stationary position and would probably drift downstream and settle into areas
with lower velocities
(as with pools). Unequal probabilities
of capture among
river sections during the first sampling event is also inherent, especially in
the lower river section.
This section tends to be more difficult
to sample
due to its general morphometry: river velocity is slower, water is deeper and
more turbid, there are fewer gravel bars, and there are more fallen trees.
These factors make it difficult
to see and capture chinook salmon during both
sampling events.
The sampling design was set up such that equal fishing
effort was expended in each of the three river areas during both sampling
events, and the intent was to estimate abundance using the Chapman model.
Allocating proportionally
more sampling effort in one or more river sections
would require that a stratified
estimator be used. While this design
modification might alleviate problems with capture probabilities
or mixing, it
would most likely result in a less accurate estimate of abundance than if an
unstratified
estimator was used, or it would cost more in terms of sampling
effort.
Bias of the abundance estimate associated
with tag losses in this
investigation
and similar studies (Skaugstad 1988, 1989, 1990a, and 1990b;
Evenson 1991; Burkholder 1991) was minimal or nonexistent.
The jaw tags were
securely attached around the lower jaw (dentary bone) and decomposition of the
flesh did not facilitate
tag loss. The three tags that were lost in this
experiment were easily identified by the presence of fin-clips.
Too few carcasses were collected to estimate all proportions of male and
female chinook salmon by age class within the objective criteria for accuracy
and precision (within five percentage points of the actual proportions 95% of
the time).
To meet these criteria,
193 additional carcasses were needed
(Thompson 1987). Because both samples were combined to estimate length and
sex compositions, objective criteria for estimating these proportions (same as
above) were achieved.
Accurate estimation of the proportions
of female
chinook salmon by length categories in turn provided an accurate estimate of
population egg production (relative precision = 15%). The same methodology
(mark by electrofishing,
recapture by collecting carcasses) has been used to
estimate age-sex-size compositions in the Salcha River since 1987 (Skaugstad
1988, 1989, 1990b, and In press; Burkholder 1991) and in the Chena River since
1989 (Skaugstad 1990a: Evenson 1991, and this study).
These studies have
indicated that there is generally no sex selectivity
within either sampling
event.
When there is size selectivity,
it is typically
during the
electrofishing
event. The best way to ensure that all objective criteria are
met for age-sex-size compositions in the future is to establish sample sizes
based on the carcass sampling event.
-22-
Attempts to estimate a relationship
between the proportion of the population
of chinook salmon observed during aerial surveys and estimates of abundance
from mark-recapture
experiments indicate that: (1) there is an inverse
relationship
between the proportion of the population observed during an
aerial survey and the size of the population; and, (2) the proportion of the
population observed during an aerial survey is dependant on environmental
factors and timing of the survey relative to peak spawning. Because of the
various effects of these factors, the number of paired aerial surveys and
mark-recapture experiments since 1986 does not yet provide enough information
to adequately describe the relationship.
ACKNOWLEDGEMENTS
I wish to thank Dave Stoller, Robert Silas, Peggy Merritt, Naomi Morton, Bill
Leslie, and Jerry Pilot for assisting with field work and data collection.
Marianna Alexandersdottir,
Peggy Merritt,
John Clark, and Kelly Hepler
reviewed the data analysis and draft report.
Renate Riffe aged all scale
samples. Sara Case completed final edits and prepared the manuscript for
publication.
This investigation
was financed by the Federal Aid in Fish
Restoration Act (16 U.S.C. 777-777K) under project F-10-7, Job No. S-3-l(a).
LITERATURE CITED
Baker, T. T. 1988. Creel censuses in Interior Alaska in 1987. Alaska Department of Fish and Game. Fishery Data Series No. 64, Juneau. 138 PP.
-*
1989. Creel censuses in Interior Alaska in 1988. Alaska Department
of Fish and Game. Fishery Data Series No. 95, Juneau. 110 pp.
Barton, L. H. 1987a. Population estimate of chinook salmon escapement in the
Chena River in 1986 based upon mark and recapture techniques.
Alaska
Department of Fish and Game, Division of Commercial Fisheries,
Fairbanks. Arctic, Yukon, and Kuskokwim Region, Yukon Salmon Escapement
Report No. 31. 38 pp.
-*
1987b. Yukon area salmon escapement aerial survey manual. Alaska
Department of Fish and Game, Division of Commercial Fisheries,
Fairbanks.
Arctic, Yukon, and Kuskokwim Region, Yukon River Salmon
Escapement Report No. 33. 14 PP.
-*
1988. Population estimate of chinook salmon escapement in the Chena
River in 1987 based upon mark and recapture techniques.
Alaska
Department of Fish and Game, Division of Commercial Fisheries, Regional
Information Report No. 3F88-05.
Barton, L. H. and R. Conrad. 1989. Population estimate of chinook salmon
escapement in the Chena River in 1988 based upon mark and recapture
techniques.
Alaska Department of Fish and Game, Division of Commercial
Fisheries, Regional Information Report No. 3F89-13.
-23-
LITERATURE CITED (Continued)
Burkholder,
A.
1991.
composition of the
Alaska Department
Anchorage. 32 PP.
Abundance, egg production,
and age-sex-length
chinook salmon escapement in the Salcha River, 1990.
of Fish and Game. Fishery Data Series No. 91-5,
Chapman, D. 1951. Some properties of the hypergeometric
applications
to zoological
censuses. University
Publications in Statistics.
No. 1:131-160.
distribution
with
of California
Clark, R. A. 1985. Evaluation assessment in Alaska lakes. Fairbanks, Alaska. 180 pp.
of sampling gears for fish population Master's Thesis. University of Alaska,
Clark, R. A., and W. P. Ridder.
1987. Tanana Drainage creel census and
harvest surveys, 1986. Alaska Department of Fish and Game. Fishery
Data Series No. 12, Juneau. 91 pp.
Clutter, R. I. and L. E. Whitesel.
1956. Collection and interpretation
of
sockeye salmon scales.
Bulletin of the International
Pacific Salmon
Fisheries Commission 9, Vancouver, British Columbia.
Darroch, J. N. 1961. The two-sample capture-recapture
census when tagging
and sampling are stratified.
Biometrika 48:241-260.
Efron, B. and G. Gong. 1983. A leisurely
look at the bootstrap,
the
jackknife,
and cross-validation.
The American Statistician,
37(l).
48 PP.
Evenson, M. J. 1991. Abundance, egg production, of the chinook salmon escapement in the Department of Fish and Game. Fishery Data 35 PP.
and age-sex-size composition Chena River, 1990. Alaska Series. No. 91-6, Anchorage.
Goodman, L. A. 1960. On the exact variance of products.
Statistical
Association, 55:708-713.
Journal of American
Hallberg, J. E. and A. E. Bingham. 1991. Creel surveys conducted in interior Alaska during 1990. Alaska Department of Fish and Game. Fishery Data Series. No. 91-56, Anchorage. 98 PP.
Hallberg, J. E. and A. E. Bingham. In press.
Creel surveys in interior
Alaska during 1991. Alaska Department of Fish and Game. Fishery Data
Series.
Mills, M. J. 1979. Alaska statewide sport fish harvest studies.
Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1977-1978. Project F-9-11, 20(SW-I-A):112 pp.
-24-
LITERATURE CITED (Continued)
--
1980. Alaska statewide sport fish harvest studies (1979). Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1979-1980. Project F-9-12, 21(SW-I-A):65 pp.
-*
1981. Alaska statewide sport fish harvest studies (1980). Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1980-1981. Project F-9-13, 22(SW-I-A):78 pp.
--
1982. Alaska statewide sport fish harvest studies (1981). Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1981-1982. Project F-9-14, 23(SW-I-A):115 pp.
--
1983. Alaska statewide sport fish harvest studies (1982). Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1982-1983. Project F-9-15, 24(SW-I-A):118 pp.
--
1984. Alaska statewide sport fish harvest studies (1983). Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1983-1984. Project F-9-16, 25(SW-I-A):122 pp.
--
1985. Alaska statewide sport fish harvest studies (1984). Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1984-1985. Project F-9-17, 26(SW-I-A):122 pp.
--
1986. Alaska statewide sport fish harvest studies (1985). Alaska
Department of Fish and Game. Federal Aid in Fish Restoration, Annual
Report of Progress, 1985-1986. Project F-10-1, 27(RT-2):137 pp.
-*
1987. Alaska statewide sport fish harvest report. Alaska Department
of Fish and Game. Fishery Data Series No. 2, Juneau. 140 pp.
--
1988. Alaska statewide sport fish harvest report. Alaska Department
of Fish and Game. Fishery Data Series No. 52, Juneau. 142 pp.
-*
1989. Alaska statewide sport fish harvest report. Alaska Department
of Fish and Game. Fishery Data Series No. 122, Juneau. 142 pp.
1990. Harvest and participation
in Alaska Sport Fisheries during
-'1989.
Alaska Department of Fish and Game. Fishery Data Series No. 90-
44, Anchorage. 152 pp.
1991. Harvest and participation
in Alaska Sport Fisheries during
-'1990.
Alaska Department of Fish and Game. Fishery Data Series No. 91-
58, Anchorage. 183 pp.
Merritt, M. F., A. Bingham, and N. Morton. 1990. Creel surveys conducted in Interior Alaska during 1989. Alaska Department of Fish and Game. Fishery Data Series No. 90-54, Anchorage. 125 pp.
-25-
LITERATURE CITED (Continued)
Seber, G. A. F. 1982. The estimation of animal abundance and related parameters. Charles Griffin and Company, Ltd. 654 pp.
Skaugstad, C. L. 1988. Abundance and age-sex-size composition Salcha River chinook salmon escapement. Alaska Department Game, Fishery Data Series No. 37, Juneau. 25 PP.
of the 1987 of Fish and
--
1989. Abundance and age-sex-size composition of the 1988 Salcha River
chinook salmon escapement. Alaska Department of Fish and Game, Fishery
Data Series No. 75, Juneau. 30 PP.
-*
1990a. Abundance, egg production, and age-sex-size composition of the
chinook salmon escapement in the Chena River, 1989. Alaska Department
of Fish and Game, Fishery Data Series No. 90-13, Anchorage. 32 PP.
--
1990b. Abundance, egg production, and age-sex-size composition of the
chinook salmon escapement in the Salcha River, 1989. Alaska Department
of Fish and Game, Fishery Data Series No. 90-23, Anchorage. 32 PP.
--
In press. Abundance, egg production, and age-sex-length composition
of the chinook salmon escapement in the Salcha River, 1991. Alaska
Department of Fish and Game, Fishery Data Series.
Skaugstad, C. L. and B. McCracken. 1991. Fecundity of chinook salmon, Tanana River, Alaska. Alaska Department of Fish and Game, Fishery Data Series No. 91-8, Anchorage. 28 PP.
Thompson, S. K. 1987. Sample sizes for
parameters of multinomial
proportions.
41(1):42-47.
simultaneously
estimating the
The American Statistician
-26-
APPENDIX A -27-
Appendix
Al. Statistical
tests for analyzing data from a mark-recapture
+ experiment for gear bias, and for evaluating the assumptions
of a two-event mark-recapture experiment.
The following
statistical
tests will be used to analyze the data for
significant
bias due to gear selectivity
by sex and length:
1. A test for significant
gear bias by sex will be based on a contingency
table of the number of males and females that were recaptured and were
not recaptured.
The chi-square statistic
will be used to evaluate the
bias.
If Test 1 indicates a significant
bias, the following tests will be done for
males and females, separately.
If Test 1 does not indicate a significant
bias, males and females will be combined and the following tests will be done.
2. Tests for significant
gear bias by size will be based on:
(A) Kolmogorov-Smirnov goodness of fit test comparing the distributions
of the lengths of all fish that were marked during electrofishing
and
all marked fish that were collected during the carcass survey; and,
(B) Kolmogorov-Smirnov two sample test comparing the distributions
of
the lengths of all fish that were captured during electrofishing
and all
fish that were collected during the carcass survey. The null hypothesis
is no difference between the distributions
of lengths for Test A or for
Test B.
For these two tests there are four possible outcomes:
Case I: Accept H,(A) There is no size-selectivity were marked) or during the collected).
during second
Accept H,(B) the first sampling event (when fish sampling event (when carcasses were
Case II:
Accept H,(A)
There is no size-selectivity
is size-selectivity
during
during the first
Reject H,(B) the second sampling event but there sampling event.
Case III:
Reject H,(A)
Accept H,(B)
There is size-selectivity
during both sampling events.
Case IV:
Reject H,,(A)
Reject H,(B)
There is size-selectivity
during the second sampling event;
of size-selectivity
during the first event is unknown.
the status
-continued-
-28-
Appendix Al. (Page 2 of 4).
Depending on the outcome of the tests, the following to estimate the abundance of the population:
procedures will be used
Case I:
Calculate one unstratified
estimate of abundance, and pool
lengths, sexes, and ages from both sampling events to improve
precision of proportions in estimates of compositions.
Case II:
Calculate one unstratified
estimate of abundance, and only
use lengths, sexes, and ages from the second sampling event
to estimate proportions in compositions.
Case III:
Completely stratify both sampling events, and estimate the abundance for each stratum. Add the estimates of abundance across strata to get a single estimate for the population. Pool lengths, ages, and sexes from both sampling events to improve precision of proportions in estimates of composition, and apply formulae to correct for size bias to the pooled data.
Case IV:
Completely stratify
both sampling events and estimate the
abundance for each stratum. Add the estimates of abundance
across strata to get a single estimate for the population.
Also, calculate a single estimate of abundance without
stratification.
Case IVa:
If the stratified
and unstratified
estimates of abundance for
the entire
population
are dissimilar,
discard
the
unstratified
estimate. Only use the lengths, ages, and sexes
from the second sampling event to estimate proportions in
composition, and apply formulae to correct for size bias (See
Adjustments in Compositions for Gear Selectivity)
to data
from the second event.
Case IVb:
If the stratified
and unstratified
estimates of abundance for
the entire population are similar, discard the estimate with
the larger variance.
Only use the lengths, ages, and sexes
from the first sampling event to estimate proportions
in
compositions, and do not apply formulae to correct for size
bias.
-continued-
-29-
Appendix Al. (Page 3 of 4).
Closed Population
The following two assumptions must be fulfilled:
1. Catching and handling the fish does not affect the probability
of
recapture; and,
2. Marked fish do not lose their mark.
Catching and handling the fish should not affect the probability
of recapture
because the experiment is designed to mark live fish and later recover
carcasses. If the jaw tag is lost, the fin clip given each fish will identify
the river section where it was marked.
Of the following assumptions, only one must be fulfilled:
1.
Every fish has an equal probability
of being marked and released during
electrofishing;
2. Every fish has an equal probability carcass survey; or,
of being collected during the
3. Marked fish mix completely with unmarked fish between electrofishing
and
carcass surveys.
To evaluate these three assumptions, the chi-square statistic will be used to
examine the following contingency table.
The results will be used to
determine the appropriate abundance estimator and if the estimate of abundance
should be stratified
by river section or period:
1. Null hypothesis is that marked-to-unmarked ratio is the same at all
sites. Columns 1, 2, and 3 in the table will be the corresponding river
section where the fish were recovered.
Row 1 will be the number of
marked fish collected during the carcass sampling event and row 2 will
be the number of unmarked fish collected during the carcass sampling
event. The column totals will be equal to the number of fish marked
during the electrofishing
event.
-continued-
-3o-
Appendix Al. (Page 4 of 4).
If the test statistic
is not significant,
then either every fish had an equal
probability
of being marked (caught in the electrofishing
gear) or marked fish
mixed completely with unmarked fish between sampling events. In this case a
Petersen estimate will be used to estimate abundance. If the test statistic
is significant
the following matrix will be created:
River Section of Release Lower Middle Upper
River Section of Recapture
Lower
Middle
Upper
If all the off-diagonal
elements are zero, then a Petersen estimate will be
calculated for each river section. The sum of the three estimates will be the
overall abundance estimate.
If the off-diagonal
estimates are not zero, then
Darroch's method will be used to estimate abundance. With these tests it is
unknown whether the second assumption was fulfilled.
Darroch's method will be
used to insure an unbiased estimate.
-31-
APPENDIX B -32-
Appendix
Bl. Estimates of the proportions of female and male chinook salmon
by age class, and mean length-at-age
estimates for chinook
salmon sampled in the Goodpaster River, 1991.
Age Class Females: 1.2 1.3 1.4 1.5 Totals
Sample Size 1 9 16 4 30
Proportion of Sample
Standard Error
0.012 0.107 0.190 0.048 0.357
0.012 0.034 0.043 0.023 0.053
Mean Length
Standard Error
575
737
14
828
14
909
14
803a
16
Males:
1.2
5
1.3
35
1.4
12
1.5
2
Totals
54
0.060 0.417 0.143 0.024 0.643
0.026 0.054 0.038 0.017 0.053
572
13
728
12
827
14
975
25
744b
14
Males
and Females:
1.2
6
1.3
44
1.4
28
1.5
6
Totals
84
0.071 0.524 0.333 0.071 1.000
0.028 0.055 0.052 0.028
573
11
729
10
827
10
931
18
768c
10
* Total sample size was 34 and included four female chinook for which an age was not assigned. b Total sample size was 57 and included three male chinook for which an age was not assigned. c Total sample size was 93 and included seven chinook for which an age was not assigned and two chinook for which neither sex nor age was assigned.
-33-
Appendix B2. Length compositions of male and female chinook salmon carcasses sampled in the Goodpaster River, 1991.
Length Category
Sample Size
Proportion of Sample
Standard Error
Female:
<500
0
500-549
0
550-599
1
600-649
0
650-699
3
700-749
6
750-799
5
800-849
7
850-899
8
900-949
3
950+
0
Totals:
33
Male:
<500
1
500-549
1
550-599
5
600-649
2
650-699
6
700-749
13
750-799
16
800-849
6
850-899
5
900- 949
2
950+
1
Totals:
58
Female and Male:
<500
1
500-549
1
550-599
6
600-649
2
650-699
9
700-749
19
750-799
22
800-849
13
850-899
14
900-949
5
950+
1
Totals:
93a
0 0 0.011 0 0.033 0.066 0.055 0.077 0.088 0.033 0 0.363 0.011 0.011 0.055 0.022 0.066 0.143 0.176 0.066 0.055 0.022 0.011 0.637 0.011 0.011 0.065 0.022 0.097 0.204 0.237 0.140 0.151 0.054 0.011 1.000
0 0 0.011 0 0.018 0.026 0.024 0.028 0.029 0.018 0 0.051 0.011 0.011 0.024 0.015 0.026 0.036 0.039 0.026 0.024 0.015 0.011 0.051 0.011 0.011 0.026 0.015 0.031 0.042 0.044 0.036 0.037 0.024 0.011 0
a Total sample included two fish for which sex was not determined.
-34-
,_. I_____l__qrr_l-..
___-_*_
--.-
J-c-r_-_____/_-l_-lc--.-~
.-_--
___
. . ..-
__-----
..--..._.
_ ---.-.--....--
-..-.
. .~_.
APPENDIX C -35-
Appendix
Cl. Age, length,
and sex data collected
carcasses in the Chatanika River, 1991.
Date of Collection
Sex
Length
7/13/91 a/08/91 8/08/91 8/08/91 8/08/91 8/08/91 8/08/91 8/08/91
Unknown
693
Unknown
840
Male
790
Male
830
Female
790
Female
810
Female
900
Female
930
from chinook
salmon
Age 1.3 1.5 1.3 1.4 1.4 1.4 1.5 1.5
-36-

MJ Evenson

File: abundance-egg-production-and-age-sex-size-composition-of-the.pdf
Title: Abundance, Egg Production, and Age-Sex-Size Composition of the Chinook Salmon Escapment in the Chena River, 1991
Author: MJ Evenson
Author: Evenson, Matthew J.
Keywords: Fds92-04
Published: Mon Aug 24 08:09:10 1998
Pages: 47
File size: 2.06 Mb


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