Simulation of the combined effects of artisanal and recreational fisheries on a Mediterranean MPA ecosystem using a trophic model

Abstract

Marine protected areas (MPAs) have the potential to enhance the long-term sustainabil- ity of coastal resources, and the artisanal fisheries which depend on them. However, recreational fisheries, which are increasing their impacts on coastal resources worldwide, may reduce the bene- fits that MPAs provide to declining artisanal fisheries. Here we used the Bonifacio Straits Natural Reserve (BSNR) Corsica as a study case to simulate the combined effects on coastal resources of arti- sanal and recreational fishing efforts. The BSNR ecosystem was modelled using mass-balance mod- elling of trophic interactions. This model was compared to another built on a non-protected area from the same region. We aggregated fishing fleets into artisanal and recreational categories, and we sim- ulated various combinations of fishing effort over a 20 yr dynamic simulation using Ecosim. We showed that fishing activities have an additional top-down effect on the food web and that they decrease the targeted group's biomass, such as piscivorous species. We found, for some trophic groups, non-trivial patterns of biomass variation through trophic cascades. Our trophic approach revealed that some groups may suffer a biomass decrease when MPAs are set or enforced, due to the combined effect of artisanal and recreational fisheries. Overall, our results illustrate the value of mod- elling to manage MPAs, as a complementary tool to surveys. Models provide the opportunity to anti- cipate the potential consequences, at the ecosystem level, of socio-political decisions that aim to sustain coastal resources while managing artisanal and recreational fisheries.