Two Demersal Trawl Surveys in the Gulf of Alaska: Implications of Survey Designand Methods

摘要

Bottom trawl surveys of groundfish stocks in the Gulf of Alaska are executed on atriennial basis as a joint responsibility of the Resource Assessment and Conservation Engineering (RACE) Division and the Auke Bay Laboratory (ABL), both of the Alaska Fisheries Science Center (AFSC). For each survey, the authors describe its design, the methods used to execute the survey, and methods of analysis that were applied to the data. The authors provide the information an analyst needs to render these surveys comparable to each other and to future surveys. Also of importance is an account of the history of estimation of indices of abundance based on data from these surveys, particularly the history of the use of fishing power corrections (FPCs). Data from each survey have advanced through three analyses, each time reflecting a change in the understanding of the peculiarities of the surveys and changes in estimation methods, particularly with respect to FPCs. The authors state the strategy for estimating and applying FPCs which has evolved, including a narrow definition of the term 'negligible' as it refers to differences in fishing efficiency. The authors outline elements of an ideal multispecies bottom trawl survey in the Gulf of Alaska.