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Genetic stock composition analysis of Chinook salmon bycatch samples from the 2014 Gulf of Alaska trawl fisheries

Abstract

A genetic analysis of samples from the Chinook salmon (Oncorhynchus tshawytscha) bycatch of the 2014 Gulf of Alaska (GOA) trawl fisheries for walleye pollock (Gadus chalcogrammus), rockfish (Sebastes spp.), and arrowtooth flounder (Atheresthes stomias) 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 (ADF&G) SNP baseline. In 2014, genetic samples were collected from Chinook salmon taken in the bycatch of the Gulf of Alaska (GOA) pollock trawl fisheries using a simple random sample protocol with trip being the primary unit. This is the first year for this sampling protocol and resulted in the largest available genetic sample set to date with 10.7% of the salmon bycatch successfully genotyped.  Based on the analysis of 1,163 Chinook salmon bycatch samples, British Columbia (43%), West Coast U.S. (35%), Coastal Southeast Alaska (16%), and Northwest Gulf of Alaska stocks (5%) comprised the largest stock groups.  Weighting the available sample sets to the total bycatch by season and statistical area did not appreciably change the overall stock composition.  

In 2014, genetic samples from the bycatch of the rockfish catcher vessel (CV) fishery in the central GOA were collected by the fishing industry using a census sampling protocol where every Chinook salmon encountered was sampled.  Based on the genotyping of 398 Chinook salmon bycatch samples collected from the 2014 GOA rockfish CV trawl fishery in NMFS Statistical Areas 620 and 630, West Coast U.S. stocks (WA/OR/CA) represented the largest stock grouping (72%) with smaller contributions from British Columbia (17%), Coastal Southeast Alaska (7%), and Northwest GOA (3%) stocks. Based on the genotyping of 404 Chinook salmon bycatch samples collected throughout the 2014 GOA arrowtooth flounder trawl fishery from the catcher-processors (CP) FV Vaerdal and FV US Intrepid; West Coast U.S. stocks (WA/OR/CA) represented the largest stock grouping (51%) with smaller contributions from British Columbia (36%), Coastal Southeast Alaska (10%), Northeast GOA (2%) and Northwest GOA (2%) stocks.  



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