The Role of Elasmobranchs in the Cantabrian Sea Shelf Ecosystem and Impact of the Fisheries on Them

Elasmobranchs apparently play an ecological role of relevance in the demersal community of the Cantabrian Sea. Using biomass indices obtained from bottom trawl surveys the most significant elasmobranch species in the continental shelf ecosystem are described. By combining their spatial distribution with multivariate analysis, including other fish species, it is possible to place them within the communities that structure the ecosystem. Considering all the fish species inhabiting the continental shelf and applying a trophodynamic model which incorporates biomass, production, biological parameters, feeding diets and catches and discards of the fisheries, the trophic level of the main elasmobranch groups and their relationship with others species inhabiting the same area are obtained. Also an estimation of the impact of the different fisheries (gears) that operate in the study area is made. Finally, some time-spatial simulations of the consequences of some management measurements affecting elasmobranch populations such fishery closed areas, have been performed. The results of these simulations are validated in situ by carrying out experiments in a closed area located in the central Cantabrian Sea shelf