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Using Multiple Data Sets to Assess Red King Crab in Norton Sound, Alaska: Length-Based Stock Synthesis

Using Multiple Data Sets to Assess Red King Crab in Norton Sound, Alaska: Length-Based Stock Synthesis

J. Zheng, G.H. Kruse, and L. Fair

Using Multiple Data Sets to Assess Red King Crab in Norton Sound, Alaska: Length-Based Stock SynthesisThis is part of Fishery Stock Assessment Models
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Description

Red king crab, Paralithodes camtschaticus, in Norton Sound, Alaska, support three fisheries: summer commercial, winter commercial, and winter subsistence fisheries. Four types of surveys have been conducted periodically during the last two decades: summer trawl, summer pot, winter pot, and preseason summer pot, but none of these surveys were conducted every year. To improve abundance estimates, we developed a length based stock synthesis model of male crab abundance that combines multiple sources of survey, catch, and mark-recovery data from 1976 to 1996. A maximum likelihood approach was used to estimate abundance, recruitment, and catchabilities of the commercial pot gear. The model yielded a time series of abundance that is smooth and consistent over time. Estimates of parameters and legal crab abundance are not very sensitive to weighting factors for survey abundances and fishing effort, and maximum effective sample size. Assumed natural mortality influenced recruitment estimates, but had limited impact on estimates of legal abundances. The model can be used to improve fisheries management by reducing annual variations in catch and the risk of overfishing.

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