Modelización ecológica del Mediterráneo noroccidental: estructura del ecosistema e impactos de la pesca

A mass-balance model was developed to characterize the structure and functioning of the marine continental shelf and slope area of the Northwestern Mediterranean Sea, from the Toulon to Cape La Nao (NWMS model). The model has been built from previous applications of Ecopath with Ecosim in areas of the Northwestern Mediterranean (Gulf of Lions and South Catalan Sea). The model represented the ecosystem in the early 2000s, covered 45547 km 2 , and included depths from 0 to 1000 m. The study area was chosen to specifically account for the connectivity between these areas and the shared fish stocks. Furthermore, the results have been compared with several ecosystems models developed in the Mediterranean Sea and the Gulf of Cadiz and various management scenarios have been analyzed. Input data were based on local scientific surveys and fishing statistics, published data on stomach content analyses, and the application of empirical equations. The model was composed of 54 functional groups, including all trophic levels, and considering several Spanish and French fleets. Results highlighted that the main trophic flows are related to detritus, phytoplankton, zooplankton and benthic invertebrates. Dolphins, benthopelagic cephalopods, demersal fishes large (continental shelf), large pelagic fishes and salema were identified to be key species/groups of the Ecosystem. Results confirmed that the fishing impact is high and widespread throughout the whole food web so the ecosystem is very exploited. The comparative approach confirmed the spatial productivity pattern for the Mediterranean Sea and the Gulf of Cadiz. Furthermore, compared ecosystems share some common features in structure and function such as the important role of detritus, the dominanace of pelagic fraction in terms of flows, a strong benthic-pelagic coupling and hight impact of fishing. Management simulations illustrated the importance of integrated management of marine ecosystems, the risk of an increase in fishing effort and the potential benefits of a moderate reduction of fishing effort in the study area.