GENETIC ESTIMATES OF STOCK COMPOSITIONS OF 



1983 CHINOOK SALMON, ONCORHYNCHUS TSHAWYTSCHA, HARVESTS 



OFF THE WASHINGTON COAST AND THE COLUMBIA RIVER 



Fred Utter,' David Teel,' George Milner,' and 

 Donald McIsaac^ 



ABSTRACT 



Allele frequency data for 17 polymorphic protein coding loci from 88 populations of chinook salmon 

 between British Columbia, Canada and California, U.S.A. were used to obtain maximum likelihood 

 estimates of contributing populations to fisheries off the coast of Washington, U.S.A. Data were available 

 for the commercial troll fishery of May 1982 and for commercial, Indian, and sport fisheries during spring 

 and summer 1983. The estimated contributions of fall run fish returning to areas of the lower Columbia 

 River (collectively called "tules") to the May troll fisheries were 76.5% in 1982 and 54.9% in 1983. In 

 contrast, the estimated proportion of fall run fish destined for areas of the upper Columbia River (collec- 

 tively called "upriver brights") was less than 5% in both years, although these runs are known to make 

 substantial contributions to more northern fisheries of Canada and Alaska. A considerable difference 

 for each year occurred in the estimated proportion of California fish (2.8% in 1982 and 18.7% in 1983). 

 Differences occurred among the fisheries and areas sampled in 1983. Larger estimates for Canadian 

 and Puget Sound (Washington) fish occurred in fisheries of northern areas; the largest was 41% for the 

 Indian fishery in the Strait of Juan de Fuca. A greater proportion of California fish in any particular 

 area was taken in sport fisheries. The subset of tule populations returning to the Kalama and Cowlitz 

 river drainages was harvested at a higher rate in sport than commercial fisheries. This study demonstrates 

 the capabilities of the involved procedures for generating timely and reliable estimates of stock composi- 

 tion, and serves as a starting point for more detailed understandings of the oceanic distribution of chinook 

 salmon populations. 



Chinook salmon, Oncorhynchus tshawytscha, runs 

 returning to Pacific drainages of the western United 

 States are a major biological, recreational, and eco- 

 nomic resource. Their importance persists in spite 

 of the often excessive harvests, disruptions of habi- 

 tats, and blockages of migratory routes that have 

 occurred during the past century. The vitality of 

 these runs continues to fluctuate under the influence 

 of many factors. Conflicting demands of multiple 

 user groups, including recreational, commercial, 

 native American, and international fishing interests, 

 tend to stress the overall resource. Water require- 

 ments for energy, irrigation, and human consump- 

 tion often conflict v^ith even minimal conditions for 

 fish rearing, passage, and reproduction. Instabilities 

 of nature in freshwater and marine environments 

 also contribute substantially to fluctuations in 

 growth, migration, and survival. 

 The management of this resource is further com- 



'Northwest and Alaska Fisheries Center Montlake Laboratory, 

 National Marine Fisheries Service, NOAA, 2725 Montlake Boule- 

 vard East, Seattle, WA 98112. 



^Columbia River Laboratory, Washington Department of Fish- 

 eries, P.O. Box 999, Battle Ground, WA 98604. 



plicated by the ecological and genetic diversity of 

 its individual populations. For instance, fish har- 

 vested off the Washington coast represent a com- 

 plex and continually changing mixture of stocks 

 destined for many areas (Fig. 1; see also Miller et 

 al. 1983). Runs returning to the Columbia River illus- 

 trate this diversity; here freshwater entry extends 

 from February through October, and upstream 

 migration distances range from virtually nothing to 

 many hundreds of miles. 



The largest numbers of Columbia River chinook 

 salmon return in the fall and consist of two distinct 

 types. Fish of that segment of the run commonly 

 called "brights" retain the silver color of ocean- 

 caught salmon for extended periods following their 

 freshwater entry and return primarily to areas 

 above The Dalles Dam. Brights are largely main- 

 tained by natural reproduction with hatchery supple- 

 mentation of some segments. Fish of the largest seg- 

 ment of the fall run are referred to as "tules"; they 

 approach spawning condition rapidly as soon as, and 

 often before, they enter fresh water. Tules return 

 to areas below The Dalles Dam and are perpetuated 

 almost entirely by hatcheries. Although both tules 



Manuscript accepted October 1986. 

 FISHERY BULLETIN: VOL. 85, NO. 1, 1987. 



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