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Economics & Social Sciences Research Program

Two-stock Bioeconomic Model for Estimating Joint Economic Yield of Bristol Bay Red King Crab and Eastern Bering Sea Snow Crab 

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Oct-Nov-Dec 2012
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Maximum sustainable yield (MSY) is the default reference point in U.S. fisheries management. However, optimum yield is the amount of fish that provides the greatest overall benefit to the nation, which could be lower than MSY because of economic or other factors. To analyze relationships between MSY and maximum economic yield (MEY), the stock assessment methods used to provide management advice for Bristol Bay red king crab (Paralithodes camtschaticus) and eastern Being Sea snow crab (Chionoecetes opilio) were linked with an economics module. This two-stock bioeconomic model relates fishing mortality in each directed pot fishery to days fishing and variable costs related to fuel, food, and bait (the latter by relating days fishing to the number of potlifts). This bioeconomic model was used to estimate fishing effort corresponding to MSY and MEY, as well as the sensitivity of fishing effort at these reference points to uncertainty in prices, costs, and crab population dynamics. Catch, abundance and size-composition data were also modeled using simplified (i.e., 5-size-class) population dynamics, and these simplified population dynamics were used as the basis for a two-stock bioeconomic model. The full and simplified bioeconomic models were used to evaluate the sensitivity of the estimates of management reference points to the structure of the assessment model and to explore the impact of constraints on total effort on the joint yield and profit for these two fisheries. The bioeconomic models were also used to assess the optimal split of total effort between the Bristol Bay red king crab and eastern Bering Sea snow crab fisheries given different levels of total effort and three alternative management objectives: 1) maximizing long-term catch, 2) maximizing long-term profit, and 3) maximizing net present value. Finally, the bioeconomic models were used as an operating model in a management strategy evaluation to illustrate how control rules, including rules with an economic foundation, can be tested for multi-stock crab fisheries.

By Mike Dalton

 

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