Alaska Department of Fish and Game, Special Publication No. 12-12, Anchorage
Uncertainty about the magnitude, frequency, location, and timing of stock-specific chum and sockeye salmon harvest in Western Alaska fisheries was the impetus for the Western Alaska Salmon Stock Identification Program (WASSIP). The program was designed to use genetic data for mixed stock analysis (MSA) of fisheries samples to more clearly describe harvest patterns of chum and sockeye salmon stocks in Western Alaska fisheries. Stock composition estimates for temporal strata across fisheries are required to estimate stock-specific harvest numbers and rates. This report describes the methods used to estimate stock compositions for chum salmon, presents stock composition estimates, and provides guidance on how to interpret biases documented in MSA baseline tests when evaluating stock composition estimates of WASSIP catch samples. For WASSIP chum salmon analyses, 143,258 fish were sampled from harvests in 278 fishery strata distributed across time within fisheries from Chignik Area to Kotzebue Sound between 2006 and 2009. Of these, 74,445 samples were selected for analysis from 207 fishery strata between 2007 and 2009. We successfully genotyped 71,656 individual fish from 194 fishery strata for the single nucleotide polymorphism markers designated for WASSIP analyses. Trends in chum salmon stock composition estimates were observed across fisheries and within and among years. In general, fisheries to the north of the Alaska Peninsula caught chum salmon of Coastal Western Alaska origin, while fisheries along the Alaska Peninsula were composed of mixtures of stocks, with fisheries along the southern Alaska Peninsula having the greatest diversity of stocks. These results provide the most comprehensive examination of the stock composition of chum salmon in commercial and subsistence fisheries in Western Alaska.
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