Multispecies Perspectives on the Bering Sea Groundfish Fisheries Management Regime

Abstract

The need to understand the multispecies implications of various harvesting regimes is becoming more important as fishery managers move toward ecosystem-based management. We explore the possible effects that different exploitation rates may have on eastern Bering Sea groundfish using a multispecies simulation context that incorporates predator–prey relationships. At present, some groundfish species in the eastern Bering Sea are exploited up to the recommended levels of allowable biological catch, whereas others, for economic or bycatch limitation reasons, are only lightly exploited. We explore the possible long-term multispecies implications of different exploitation patterns on the biomass and yield of several groundfish species using predator−prey suitability estimates derived from multispecies virtual population analysis (MSVPA) in a multispecies simulation modeling context and compare those predictions with those from single-species forecasting models. Three different fishing scenarios that included eight species in the eastern Bering Sea were implemented in these models. In one scenario, the present exploitation rates were used for the model simulations; in the second scenario, all exploited species were more evenly exploited by fishing each species at its recommended allowable biological catch levels; and in the third scenario, there was no fishing for all the species. Results from the single-species and multispecies model simulations mostly showed the same direction of population trends. However, the magnitude of change was different for some species, which can be ascribed mainly to predation interactions. Greater differences were seen between the simulations that used the present exploitation rates and those in which no fishing occurred. The multispecies simulations that included predation interactions predicted much lower equilibrium population sizes for prey species populations under conditions of no fishing than did single-species simulations that did not take predator–prey relationships into account. These results show that multispecies models provide new insights into the implications of single-species harvesting strategies, particularly for prey species that are also the target of commercial fisheries.