Stock Composition Analysis of Salmon Bycatch Samples from the Bering Sea Aleutian Island Pollock Trawl Fishery

The incidental bycatch of Chinook and chum salmon in the Bering Sea pollock fishery and its effects on various salmon stocks in Western North America has been of concern for decades.  Identifying the stock composition of the salmon bycatch is fundamental to assessing its potential effects on regional salmon populations.  Over the last year, the Genetics Program at the AFSC Auke Bay Laboratories genetically analyzed samples from the Chinook and chum salmon bycatch and compared the DNA characteristics of the mixture against known baseline populations to determine the stock of origin.  For Chinook salmon, over 2,000 samples were analyzed over three fishery years (2007-9) and the majority of salmon originated from river systems flowing into the Bering Sea.  For chum salmon, over 6,000 salmon were analyzed over five fishery years (2005-9) and they originated from a much more diverse region throughout the North Pacific (Asia and North America).  In combination with our other studies, we are finding that salmon stocks are not uniformly distributed in the ocean as there seems to be preferences for particular stocks to occupy certain locations within the Bering Sea at different times of the year.  This information is being used to formulate policy and to better understand the potential effects of the salmon bycatch with regard to western Alaska subsistence fisheries and international treaty requirements.