UW Aquatic & Fishery Sciences Quantitative Seminar

Andre Punt

UW, SAFS

How well can FMSY and BMSY for Alaska crab stocks be estimated using empirical measures of surplus production?

Six methods based on empirical estimates of surplus production are outlined which can be used to estimate the fishing mortality and biomass corresponding to Maximum Sustainable Yield (FMSY and BMSY) for crab stocks in the Bering Sea and Aleutian Islands region of Alaska. Three of these methods involve fitting production functions to surplus production, assuming that biomass and catch are measured without error, and the other three involve computing average surplus production for biomasses close to BMSY to estimate FMSY. The six methods are tested using simulations based on data for two data-rich Alaskan crab stocks and are applied to data for six Alaskan crab stocks. The results suggest that, unlike stock status relative to the unfished level and Maximum Sustainable Yield, estimates of FMSY and BMSY are generally poor, with poor performance attributed mainly to production models ignoring transient age and size dynamics, and the impact of data contrast as well as the extent of process and observation error.