68
Paul T. Jacobson
Table 5.3. Chinook Salmon stray rates from five hatcheries on the Columbia River.
a
Brood Year
Hatchery of origin
Abernathy
Cowlitz
Kalama Falls
Lewis
Washougal
1977
11%
28%
17%
2.4%
30%
1978
15%
19%
35%
15%
21%
1979
12%
36%
6.8%
9.4%
14%
a
From T. Quinn, University of Washington School of Fisheries (unpublished data).
2.82%. The Steelhead straying rate distribution was based on data from Lirette
and Hooton (1988). The mean of 5.2% and standard deviation of 3.2% were
estimated from 5 brood-year and rearing-site combinations for which recoveries
exceeded 100 adults (110–144 fish each). The selection of these studies used to
develop the straying rates and variability of those rates was based on study design
and amount of data available. In general, the best studies were those in which most
available streams were surveyed for strays and in which multiple year classes
were studied. Although the rates for the “best” studies for Coho and Steelhead are
well within the range of rates reported in the literature, the Chinook mean rate of
18.1% from Quinn’s Columbia River data is higher than all other straying rate
values presented in the literature (T.P. Quinn, University of Washington, personal
communication). For example, Major and co-workers (1978) report Chinook
straying rates as being less than 8.4%. Quinn’s data were selected for use here
primarily because of their comprehensive nature, which allowed calculation of the
variance of the straying rate (Table 5.3, Chinook). However, results of this analysis may be biased upward for Chinook Salmon.
Sex Ratio and Age at Return
The sex ratio and parameters for percentage return by age and sex of returning
Chinook Salmon were computed from data in Fulton and Pearson (1981). The sex
ratio and sex-specific percentage return-at-age parameters used for Coho were
calculated from returns to Waddell Creek, California, between 1933 and 1939
(Shapovalov and Taft 1954). Steelhead parameters were calculated from spawning run data from two creeks on the Minnesota shore of Lake Superior in 5
consecutive years (Hassinger et al. 1974).
Distribution of Strays Among Streams
Strays are independently and identically distributed among streams in the model.
This assumption is supported by Quinn’s observations (personal communication,
University of Washington School of Fisheries) that straying is exhibited by individuals and is not influenced by group behavior. Information adequate for the
purpose of developing species-specific probability density functions (PDFs) used
for assigning each stray to a stream was very limited. The Chinook PDF is based
on data from a single natal stream and 4 brood years in the Columbia River basin
(Quinn and Fresh 1984). That study was conducted by the same principal inves-
Paul T. Jacobson
Table 5.3. Chinook Salmon stray rates from five hatcheries on the Columbia River.
a
Brood Year
Hatchery of origin
Abernathy
Cowlitz
Kalama Falls
Lewis
Washougal
1977
11%
28%
17%
2.4%
30%
1978
15%
19%
35%
15%
21%
1979
12%
36%
6.8%
9.4%
14%
a
From T. Quinn, University of Washington School of Fisheries (unpublished data).
2.82%. The Steelhead straying rate distribution was based on data from Lirette
and Hooton (1988). The mean of 5.2% and standard deviation of 3.2% were
estimated from 5 brood-year and rearing-site combinations for which recoveries
exceeded 100 adults (110–144 fish each). The selection of these studies used to
develop the straying rates and variability of those rates was based on study design
and amount of data available. In general, the best studies were those in which most
available streams were surveyed for strays and in which multiple year classes
were studied. Although the rates for the “best” studies for Coho and Steelhead are
well within the range of rates reported in the literature, the Chinook mean rate of
18.1% from Quinn’s Columbia River data is higher than all other straying rate
values presented in the literature (T.P. Quinn, University of Washington, personal
communication). For example, Major and co-workers (1978) report Chinook
straying rates as being less than 8.4%. Quinn’s data were selected for use here
primarily because of their comprehensive nature, which allowed calculation of the
variance of the straying rate (Table 5.3, Chinook). However, results of this analysis may be biased upward for Chinook Salmon.
Sex Ratio and Age at Return
The sex ratio and parameters for percentage return by age and sex of returning
Chinook Salmon were computed from data in Fulton and Pearson (1981). The sex
ratio and sex-specific percentage return-at-age parameters used for Coho were
calculated from returns to Waddell Creek, California, between 1933 and 1939
(Shapovalov and Taft 1954). Steelhead parameters were calculated from spawning run data from two creeks on the Minnesota shore of Lake Superior in 5
consecutive years (Hassinger et al. 1974).
Distribution of Strays Among Streams
Strays are independently and identically distributed among streams in the model.
This assumption is supported by Quinn’s observations (personal communication,
University of Washington School of Fisheries) that straying is exhibited by individuals and is not influenced by group behavior. Information adequate for the
purpose of developing species-specific probability density functions (PDFs) used
for assigning each stray to a stream was very limited. The Chinook PDF is based
on data from a single natal stream and 4 brood years in the Columbia River basin
(Quinn and Fresh 1984). That study was conducted by the same principal inves-