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NOAA Technical Memorandum NMFS-AFSC-288

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Evolution of observer methods to obtain genetic material from Chinook salmon bycatch in the Alaska pollock fishery


A well-designed sampling program addresses specified objectives under the realities of limited resources. Chinook salmon (Oncorhynchus tshawytscha) is a species of great importance to the people of the North Pacific. Concerns over the bycatch of this species have led to actions that increase the monitoring and data requirements for the trawl pollock (Gadus chalcogrammus) fisheries of Alaska. 

Since 2005, the North Pacific Observer Program (observer program) has collected tissues from Chinook salmon bycatch for genetic stock composition analysis.  The sampling design used to collect these tissues has changed in response to regulations that dictate how observers are deployed into the fleet.  In 2011, a systematic random sampling (SYS) of individual bycatch salmon from every trawl pollock delivery was adopted by the observer program.  This method requires that a census of Chinook salmon bycatch is achieved.  However, regulations that enable the observer program to confidently achieve a census are lacking for the Gulf of Alaska (GOA) compared to the Bering Sea and Aleutian Islands.  Consequently, a census of pollock deliveries was not obtained in the GOA during 2012 or 2013. 

Restructure of the observer program in 2013 eliminated fixed regulations governing partial observer coverage allowing for alternative sampling designs to be explored.  Simulations using seasonal data show that an alternative simple random sampling (SRS) method would have consistently resulted in the collection of more genetic tissues at a lower cost than SYS. The SRS was formally incorporated into the 2014 and 2015 sampling design of the observer program for the GOA.  The new annual process of making revisions to the observer program based on priorities and policy allows for rapid changes to the observer sampling design to meet genetic stock composition analyses and other fishery management needs.

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