Optimal Harvesting Policies Threaten Biodiversity in Mixed Fisheries

s marine ecosystems are under pressure worldwide, many scientists and stakeholders advocate the use of ecosystem-based approaches for fishery management. In particular, management policies are expected to account for the multispecies nature of fisheries. However, numerous fisheries management plans remain based on single-species concepts, such as maximum sustainable yield (MSY) and maximum economic yield (MEY), that respectively aim at maximizing catches or profits of single species or stocks. In this study, we assess the bioeconomic sustainability of multispecies MSY and MEY in a mixed fishery, characterized by technical interactions and therefore joint production. First, we analytically show how multispecies MSY and MEY can induce overharvesting and extinction of species with low productivity and low value. Second, we identify and discuss incentives on effort costs and landing prices, as well as technical regulations, that could promote biodiversity conservation and more globally sustainability. Finally, a numerical example based on the coastal fishery in French Guiana illustrates the analytical findings