Evaluating the Consequences of Alternative Atlantic Striped Bass Harvest Control Rules on Their Prey, Atlantic Menhaden

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Harvest control rules (HCRs) are automatic fishery management procedures that are agreed upon in advance and that dictate the rate of fishing that can take place. I evaluated a suite of single species and dynamic multispecies HCRs to evaluate their relative performance in achieving management goals for the striped bass (Morone saxatilis) and Atlantic menhaden (Brevoortia tyrannus) stocks using a linked, age-structured predator-prey simulation model. First, simulation model inputs were updated using the most recent stock assessment information, and striped bass length- and weight-at-age estimates were updated using otolith-based ageing data. Linear models evaluating change in striped bass length- and weight-at-age over time and between sexes identified an increase in size of as much as 30% between 1998 and 2019. Additionally, striped bass continued to grow past age-15, indicating that future striped bass stock assessments should consider expanding the number of ages included in the model. The updated predator-prey simulation model was then used to compare performance of a suite of 27 HCRs. The most influential factor determining performance of striped bass HCRs was striped bass fishing mortality (F). Atlantic menhaden had little effect on striped bass spawning stock biomass (SSB) at both high and low percent composition of Atlantic menhaden in striped bass diets. Traditional single species HCRs performed well, specifically those for which striped bass are managed at or below their target F. Although there was no single HCR that performed well for both stocks given their current reference points, both single species and dynamic multispecies HCRs that involved the “40-10 rule” for striped bass (lower threshold at 10% of unfished SSB and upper threshold at 40% unfished SSB) performed best across all striped bass performance metrics.