THE TRAWLFAUNA OF THE MAURITANIAN SHELF (NORTHWEST AFRICA) - DENSITY,SPECIES COMPOSITION, AND BIOMASS

In May 1988, epifaunal trawlsamples were collected at 17 stations on t he Mauritanian shelf off the Banc d'Arguin. The species composition an d biomass of the invertebrates and demersal fish were analysed. On the basis of species abundances, three station groups could be distinguis hed each corresponding to a subregion of the shelf. an inner shelf, a midshelf and an outer shelf station group. The average depth increased from 20 m for the inner to more than 100 m for the outer shelf statio ns. The biomass of mobile epifauna and fish was lowest on the inner sh elf stations where the trawlfauna was dominated by large sessile filte rfeeders. The trawlfaunas of the mid- and outer shelf were more simila r in species composition. Demersal fish and crustaceans appeared to be more abundant on the outer shelf. The increase in density and biomass from inner to outer shelf is discussed in relation to the distributio n of the infauna and the hydrographical conditions on the Mauritanian shelf. Being a demersal fishing area, density and biomass of the epifa una on the shelf are compared with that of the demersal fishing ground s in the southern North Sea. The result of this comparison shows that, except for echinoderms, all taxa attain higher densities and biomasse s at the Mauritanian shelf.