Genetic stock structure of odd‐year pink salmon, Oncorhynchus gorbuscha (Walbaum), from Washington and British Columbia and potential mixed‐stock fisheries applications

We used electrophoresis to determine the number and characteristics of genetically distinct stocks of odd‐year pink salmon in Washington and southern British Columbia. We analysed 5128 fish from 52 collections (taken in 1985, 1987 and 1989). We observed genetic variation at 53 enzyme‐coding loci, 19 of which were polymorphic at the P o‐95 level in at least one stock. Genotypic proportions conformed to Hardy‐Weinberg expectations in nearly all cases. The genetic profiles of individual populations were generally stable over the three cycle years studied. Significant differences in allele frequencies at sAAT‐3* , PEP‐LT* and PGDH* for several stocks were, however, noted between this study and previously reported data for pink salmon. We used G‐tests and cluster analysis of genetic distances to evaluate genetic interrelationships among collections and to define genetically distinct stocks. Differentiation among stocks exhibited a clear geographic pattern with three major clusters of stocks recognizable: (1) Hood Canal and Washington Strait of Juan de Fuca stocks, (2) Puget Sound, Fraser River, and southern Canada South Coast stocks, and (3) northern Canada South Coast stocks and Canada North Coast stocks. Computer simulations using 14 and 28 loci, and sample sizes of 15C600, demonstrated that accurate estimates of stock‐group composition could be obtained for pink salmon fisheries having a considerable range of stock compositions. The simulations revealed that approximately 50% fewer fish were required to obtain a given level of precision of stock group composition estimates with 28 loci as with the set of 14 loci used in previous investigations.