Ecosystem-based reference points under varying plankton productivity states and fisheries management strategies

In the context of ecosystem-based fisheries management, which should consider changing and uncertain environmental conditions, the development of ecosystem-based biological reference points (EBRPs) to account for important multi-species (MS) interactions, fisheryoperations, and climate change, is of paramount importance for sustainable fisheriesmanagement. However, EBRPs under varying planktonproductivity states and fisheries managementstrategies are seldom developed, and the ecosystemeffects of these changes are still largely unknown. In this study, ecosystem-based FMSY ( fishing mortalityrate at MSY) values were estimated within an end-to-end ecosystem model(OSMOSE) for three focused fish species ( Pacific Herring, Clupeapallasii; Pacific Cod, Gadusmacrocephalus; Lingcod, Ophiodon elongatus) under three planktonproductivity states of differing planktonbiomass at high, current, and low levels. In addition, ecosystemeffects were compared across different planktonproductivity and fisheries managementstrategies with the latter consisting of two fisheryscenarios (i.e. single-species-focused (SS) and MS-focused), various fishing mortalityrates, and two harvest policies (with and without harvest control rules, HCRs). Main findings of this study include: (i) planktonproductivity change affected the values of ecosystem-based FMSY, which increased as planktonproductivity states changed from low to high planktonbiomass; (ii) ecosystem-based FMSY for Pacific Herringand Pacific Codstocks increased when fisheryscenarios shifted from SS-focused to MS-focused; (iii) fisheries managementincorporating HCR yielded more stable system catch and system biomass; and (iv) high planktonbiomass combined with fisheries managementusing HCR could maintain stable ecosystemproduction and sustainable fisheries. Based on our findings, we highlight possible adaptive fisheries managementstrategies in the face of future climate and ocean changes. Overall, EBRPs complement SS stock assessmentsby incorporating key ecological processes and ecosystemproperties, thus providing supporting evidence for better incorporation of ecosystemconsiderations into scientific advice for sustainable fisheriesmanagement.