2016 Genetic stock Composition Analysis of the Chinook Salmon (Oncorhynchus Tshawytscha) Bycatch from the Bering Sea Walleye Pollock (Gadus Chalcogrammus) Trawl Fishery
Pacific salmon (Oncorhynchus spp.) are prohibited species in the federally managed Bering Sea and Gulf of Alaska (GOA) groundfish fisheries, which are subject to complex management rules (NPMFC 2017a,b) that are in part designed to reduce prohibited species catch (PSC; hereafter referred to as “bycatch”). It is important to understand the stock composition of Pacific salmon caught in these fisheries, which take place in areas that are known feeding habitat for multiple brood years of Chinook salmon (Oncorhynchus tshawytscha) from many different localities in North America and Asia (Myers et al. 2007, Davis et al. 2009). Chinook salmon are economically valuable and highly prized in commercial, subsistence and sport fisheries. Determining the geographic origin of salmon caught in federally managed fisheries is essential to understanding the effects that fishing has on Chinook salmon stocks, especially those with conservation concerns (NPFMC 2012). This report provides genetic stock identification results for the Chinook salmon bycatch samples collected from the U.S. Bering Sea (BS) walleye pollock (Gadus chalcogrammus) trawl fishery.
Amendment 91 to the North Pacific Fishery Management Council (NPFMC) Fishery Management Plan (FMP) for groundfish of the BSAI Management Area was enacted in 2010 and included retention of the all salmon caught in the pollock fishery. In 2011, a systematic random sampling design recommended by Pella and Geiger (2009) was implemented by the Alaska 2 Fisheries Science Center’s (AFSC) Fisheries Management and Analysis (FMA) North Pacific Groundfish and Halibut Observer Program (Observer Program) to collect genetic samples from one out of every 10 Chinook salmon encountered as bycatch in the BS pollock fishery.
In 2016, genetic samples were collected by the Observer Program from the Chinook salmon bycatch of the BS pollock fishery by using the systematic sampling protocols recommended previously (Pella and Geiger 2009). The number of available samples and the unbiased sampling methodology facilitated the extrapolation of the sample stock composition to the overall Chinook bycatch from the BS pollock trawl fishery in 2016. Stock composition analyses were performed using the single nucleotide polymorphism (SNP) baseline provided by the ADF&G (Templin et al. 2011), the same baseline that was used previously to estimate stock composition of samples from the 2005-2015 Chinook salmon bycatch (NMFS 2009; Guyon et al. 2010a, b; Guthrie et al. 2012-2017; Larson et al. 2013). For additional information regarding background and methodology, refer to the Chinook salmon bycatch report prepared previously for the 2008 Bering Sea trawl fishery (Guyon et al. 2010a).