Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8818
Title: Accounting for Spatial Complexities in the Calculation of Biological Reference Points: Effects of Misdiagnosing Population Structure for Stock Status Indicators
Author: Daniel R. Goethel, Aaron M. Berger
Publication Year: 2017
Journal: Canadian Journal of Fisheries and Aquatic Sciences
DOI: 10.1139/cjfas-2016-0290
Keywords: spatial population structure, biological reference points, maximum sustainable yield, overfishing, fisheries management, population dynamics, connectivity, stock assessment,

Misidentifying spatial population structure may result in harvest levels that are unable to achieve management goals.  We developed a spatially-explicit simulation model to determine how biological reference points (BRPs) differ among common population structures, and to investigate the performance of management quantities that were calculated assuming incorrect spatial population dynamics.  Simulated reference points were compared across a range of population structures and connectivity scenarios demonstrating the influence of spatial assumptions on management benchmarks.  Simulations also illustrated that applying a harvest level based on misdiagnosed spatial structure leads to biased stock status indicators, overharvesting or foregone yield.  Across the scenarios examined, incorrectly specifying the connectivity dynamics (particularly misdiagnosing source-sink dynamics) was often more detrimental than ignoring spatial structure altogether.  However, when the true dynamics exhibited spatial structure, incorrectly assuming panmictic structure resulted in severe depletion if harvesting concentrated on more productive population units (instead of being homogenously distributed).  Incorporating spatially-generalized operating models, such as the one developed here, into management strategy evaluations (MSEs) will help develop management procedures that are more robust to spatial complexities.

Theme: Sustainable, safe and secure seafood for healthy populations and vibrant communities
Foci: Provide scientific support for setting annual catch limits and measure results of annual catch limit implementation