UW Aquatic & Fishery Sciences Quantitative Seminar

Chantell Wetzel

University of Washington, School of Aquatic and Fisheries Science

Management strategy evaluation of the performance of data-moderate assessment methods for U.S. west coast groundfish

Abstract

Fisheries management in the U.S. is required to implement annual catch limits (ACLs) for all stocks included in their fishery management plans, including stocks that have not previously been assessed. ACLs have been determined for un-assessed stocks off the U.S. west coast using Depletion Corrected Average Catch (DCAC) and Depletion-Based Stock Reduction Analysis for data-limited stocks (catch data only) and Extended Depletion-Based Stock Reduction Analysis (XDB-SRA) and Extended Simple Stock Synthesis (XSSS) for data-moderate stocks (catch and index data). A management strategy evaluation is performed to evaluate the performance of each estimation method for estimating harvest levels for two life-history types (U.S. west coast flatfish and rockfish) under varying misspecifications of the parameter distributions used by the estimation methods. The probability of overfishing for both life-histories was > 0.50 at the start of the projection period when the simulated stock was depleted below the target biomass level for each estimation method (except for XSSS in select cases). XDB-SRA performed poorly for the flatfish life-history when the stock was at the target level and the index data were non-informative, resulting in overfishing due to overly optimistic estimates of relative population size. Qualitatively DCAC, XDB-SRA, and XSSS performed similarly for the rockfish life-history, with similar median population trajectories over the projected period.