Bonifacio strait natural reserve (BSNR): Investigating ecosystem functioning through comparative modelling of marine protected areas

Abstract

The Bonifacio Straits Natural Reserve (BSNR) is a Mediterranean Marine Protected Area (MPA) located in Corsica, characterized by rocky coasts, steep bathymetry, and regulated exploitation of marine resources. In this study, we updated the BSNR Ecopath model from 2010, providing a re-evaluation of the MPA's impact 13 years after the reserve's establishment and incorporating improved catch estimates, particularly for recreational fisheries. The model encompassed four primary producer groups, fourteen invertebrate groups, two Chondrichthyes groups, sixteen teleost groups, one seabird group, and one cetacean group. The BSNR model depicted a Mediterranean ecosystem where piscivorous fishes and cephalopods link primary producers to top predators (Tursiops truncatus, Dentex dentex and Epinephelus marginatus), emphasizing complex trophic relationships. Although the ecosystem faced moderate fishing pressure, the model revealed uneven pressure among groups, with rays, for example, being particularly vulnerable to fishing nets. Additionally, a mixed trophic impact analysis revealed an absence of competition among fishing fleets for resources, suggesting that, overall, recreational and artisanal fisheries do not impact each other. By comparing MPA models across the Mediterranean Sea, our research suggests that MPA establishment might enhance the overall biomass of ecosystems within their boundaries. This abundance can spill over into adjacent areas, thereby increasing biomass and diversity in those regions. In more exploited MPAs, higher values for the Finn cycling index and the consumption to total system throughput ratio indicated that fishing activities increased pressure on prey resources by diminishing the system's energy, pushing the ecosystem to optimize recycling.