2016 Genetic Stock Composition Analysis of the Chinook Salmon Bycatch Samples from the 2016 Gulf of Alaska Trawl Fisheries
The Gulf of Alaska (GOA) is known as a feeding habitat for multiple brood years of Chinook salmon (Oncorhynchus tshawytscha) originating from many different localities in North America and Asia. Determining the geographic origin and stock composition of salmon caught in federally managed fisheries is essential to understanding whether fisheries management could address conservation concerns. This report provides genetic stock identification results for Chinook salmon Prohibited Species Catch (bycatch)samples collectedin the GOA from thetrawl fisheriesfor walleye pollock (Gadus chalcogrammus) and catcher vessel (CV) trawl fisheries for rockfish (Sebastes spp.). The National Marine Fisheries Service (NMFS) and Alaska Department of Fish and Game (ADF&G) geographical statisticalareas associated with the groundfish fishery are shown in Figure 1 and are used later in the report to describe the spatial distribution of the Chinook salmon bycatch and genetic samples. Allanalyses used a single nucleotide polymorphism (SNP) baseline provided by ADF&G (Templin et al. 2011; Appendix 1),the same baseline used to estimate previous stock compositions of samples from the Chinook salmon bycatch of the federally managed GOA trawl fisheries(Guthrie et al. 2013, 2016, 2017; Guyon et al. 2014, 2015a,b; 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. 2010).
The goal of this report is to present stock composition estimates for samples collected from the bycatch of the 2016 GOA federal trawl fisheries. Owing to robust sample sizes, stock composition estimates have been applied to bycatch numbers for the first time. However, it is important to understand the limitations of each sample set for applying estimates to the entire bycatch or comparing estimates among sample sets or years.