Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 1613
Title: The performance of statistical catch-at-age model in data-limited situations and the effect of limited information
Author: Chantel R. Wetzel, A. E. Punt
Publication Year: 2011
Journal: Marine & Freshwater Research
Volume: 62
Pages: 927-936

 Limited data is a common challenge posed to fisheries stock assessment. A simulation framework was applied to examine the impact of limited data and data type on the performance of a widely used catch-at-age stock assessment method (Stock Synthesis).  The estimation method provided negatively biased estimates of current spawning stock biomass (SSB) relative to the unfished level (final depletion) when only recent survey indices were available.  Estimation of quantities of management interest (unfished SSB, virgin recruitment, target fishing mortality and final depletion) improved substantially even when only minimal length composition data from the survey were available.  However, the estimates of some quantities (final depletion and unfished SSB) remained biased (either positively or negatively) even in the scenarios with the most data (length compositions, age compositions, and survey indices).  The probability of overestimating yield at the target SSB relative to the true such yield was approximately 50%, a risk neutral result, for all the scenarios that included length composition data.  Our results highlight the importance of length composition data for the performance of an age-structured assessment model, and show encouraging results for the assessment of data-limited stocks.