Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 1772
Title: Model performance for the determination of appropriate harvest levels in the case of data-poor stocks
Author: Chantel R. Wetzel, A. E. Punt
Publication Year: 2011
Journal: Fisheries Research
Volume: 110
Pages: 342-355
Keywords: data-poor, data-limited, U.S. West Coast, groundfish, depletion-based stock reduction analysis, depletion corrected average catch, simulation, stock synthesis

The determination of harvest limits for data-poor and data-limited stocks poses unique challenges for traditional complex stock assessment methods.  Simulation is used to examine the performance of two new data-poor assessment methods, Depletion Corrected Average Catch (DCAC) and Depletion-Based Stock Reduction Analysis (DB-SRA), and a more complex catch-at-age method, Stock Synthesis (SS), in terms of estimating harvest levels for two life-history types (U.S. west coast flatfish and rockfish) under varying mis-specifications of parameter distributions.  DCAC and DB-SRA are fairly robust to mis-specification of the distributions for natural mortality and the productivity parameter (the fishing mortality rate that corresponds to maximum sustainable yield relative to natural mortality) for the flatfish life-history, but led to greater error for the rockfish life-history when estimating harvest levels that would not result in overfishing.  SS estimates of the harvest level increased when natural mortality was set to a higher value than the true value for both life-histories.  Both DCAC and DB-SRA were highly sensitive to the assumed distribution for the ratio of the current to starting biomass and provided overestimates of the harvest level when based on an overly-optimistic value for this ratio.