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NOAA Technical Memorandum NMFS-AFSC-370

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Genetic stock composition analysis of the Chinook salmon bycatch samples from the 2016 Gulf of Alaska trawl fisheries


A genetic analysis of samples from the Chinook salmon (Oncorhynchus tshawytscha) Prohibited Species Catch (bycatch) of the 2016 Gulf of Alaska (GOA) trawl fisheries for walleye pollock (Gadus chalcogrammus) and rockfish (Sebastes spp.), was undertaken to determine the stock composition of the sample sets. Samples were genotyped for 43 single nucleotide polymorphism (SNP) DNA markers and results were estimated using the Alaska Department of Fish and Game SNP baseline. In 2016, genetic samples were collected from Chinook salmon taken in the bycatch of the GOA pollock trawl fisheries using a simple random sample protocol with trip being the primary unit. This was the third year for this sampling protocol and which resulted in the largest available genetic sample set to date with 24% of the estimated salmon bycatch from the pollock fishery successfully genotyped.  Based on analysis of 4,962 Chinook salmon bycatch samples, British Columbia (42%), West Coast US (40%), and Coastal Southeast Alaska (15%) comprised the largest stock groups, at an estimated 8,602, 8,301, and 3,080 Chinook salmon, respectively, out of 20,589 fish total.  In 2016, genetic samples from the bycatch of the GOA rockfish CV fishery were collected by the fishing industry using a census sampling protocol.  Based on the genotyping of 493 Chinook salmon bycatch samples collected from this fishery in NMFS Statistical Areas 620 and 630, West Coast US stocks represented the largest stock group (62%) with smaller contributions from British Columbia (27%), Coastal Southeast Alaska (7%), and Northwest GOA (4%) stock groups.

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