Identifying research priorities for management under uncertainty: The estimation ability of the stock assessment method used for eastern Bering Sea snow crab (Chionoecetes opilio)

The fishery for snow crab in the eastern Bering Sea was declared overfished in 1999 and had by 2010 failed to rebuild in the time specified. A key component of the rebuilding plan for snow crab was the stock assessment on which management advice was based. In common with all stock assessments, there are numerous potential sources of uncertainty, but it is not clear which uncertainty is most influential, and hence how research should be focused to best reduce uncertainty. A simulation framework is used to explore the estimation ability of the assessment method when its assumptions are violated. The focus of this evaluation is on how well management quantities such as mature male biomass and the overfishing level can be estimated. Three categories of uncertainty are considered: mis-specification of pre-specified parameters, data quantity and/or quality, and assumptions in the assessment related to fishing mortality. Management quantities are estimated reasonably well when all assumptions of the stock assessment method are correct. Additional data on growth and natural mortality would be most beneficial. However, penalties on fishing mortality introduce bias into estimates, and survey selectivity patterns are poorly determined by the estimation method.