Evaluation of harvest control rules for a group of interacting commercial stocks using a multispecies MSE framework

Abstract

In this study, a multispecies gadget model (GadCap) simulating the interactions among the Flemish Cap cod (Gadus morhua), redfish (Sebastes spp.), and shrimp (Pandalus borealis) has been incorporated as the operating model in a management strategy evaluation (MSE) framework (a4a-FLR) to test the performance of multiple combinations of harvest control rules (HCRs) for the three stocks when recruitment uncertainty and assessment error are accounted for. The results indicate that due to the strong trophic interactions, it is not possible to achieve the precautionary exploitation of all the stocks at the same time. Maintaining shrimp biomass above the limit reference point (Blim) would require unsustainable fishing pressure on cod and redfish to reduce predation mortality. In contrast, maintaining cod biomass above Blim would involve high predation on and high risk of collapse of the shrimp and redfish stocks. The implementation of alternative two-stage HCRs would reduce predation, resulting in higher productivity and lower probability of collapse for cod and redfish. The results of this study support the need of accounting for species interactions when designing management strategies for a group of interdependent commercial stocks.