Deep Chondrichthyes in Mauritanian Waters

Abstract

This study analyses the sampling of 22,118 individuals and 24 tons of demersal elasmobranches caught at 243 trawling stations during four Maurit surveys, which sampled Mauritanian waters, from 84 to 1835 mdepth. We identified a total of 48 different species belonging to 17 families. Rajidae was the most diverse family (10 species), followed by the family Centrophoridae (6 species). Other diverse families were Etmopteridae, Scyliorhinidae and Somniosidae, with five species each. This chapter analyses biodiversity, community assemblages, distribution patterns and the demographic structure of the Mauritanian deepwater elasmobranches. We discuss the bathymetric ranges of the different species of the communities identified, from the shelf to the deepest part of the slope. For each community we present the geographic and bathymetric patterns of the following descriptors: biomass, abundance, richness and diversity indices. We also present spatial patterns of abundance, average sizes, length distribution and sex ratio by bathymetric range of the most abundant species (Centroscymnus coelolepis, Centroselachus crepidater, Deania calcea and Centroscyllium fabricii). Ecological constraints, environmental influence, and the direct and indirect fishing impact that shape the community structure of demersal elasmobranches are also discussed, since they play a key role in the balance and dynamics of the Mauritanian deep-sea ecosystem.