Benefits of MPA networks in the Western Mediterranean Sea: a geographically-nested ecosystem modelling approach

Abstract

We implemented a geographically-nested modelling approach to quantify the ecological and fisheries benefits of the establishment of marine protected areas (MPAs) networks in the western Mediterranean Sea. We used Ecopath with Ecosim (EwE) to develop spatial-temporal local, subregional and regional food-web models representing areas with different levels of protection. For three Mediterranean MPAs, Cerbere-Banyuls, Cap de Creus and Medes Islands, we developed nine models (three for each MPA) representing different management zones: Fully Protected Area (FPA), Partially Protected Area (PPA), and Unprotected Area (UPA). We then built three models representing each MPA zone integrating the different management schemes. Afterwards, we developed a subregional model including the three MPAs and their surroundings to describe the whole MPA network. Finally, a model covering the western Mediterranean included current general MPA dynamics. The nested modelling approach allowed us to: (1) characterize the structure and functioning of MPA zones and identify differences between zones and between MPAs, (2) assess the regional impacts of local MPAs, and (3) quantify temporal changes and explore alternative MPA spatial configurations to promote fisheries sustainability, accounting for stakeholders’ suggestions. Results highlight the ecological importance of FPAs, although their benefits are local due to their small size. Current MPAs show small differences with each other in terms of ecosystem structure and functioning. A significant increase in the level of protection and enforcement is needed to achieve positive impacts on fisheries at the regional level. This study represents a baseline for the development of further management scenarios of MPA networks