The benthos of Northwest Africa

Abstract

Information on benthos biodiversity is scarce in the CCLME and inventories of marine fauna are only available for Morocco and the Canary Islands; a regional report was recently compiled in the framework of the CCLME project. A major review of benthic biodiversity in West Africa was carried out by Le Loeuff and Von Cosel (1998), who reported the highest specific richness between Cape Blanc (Mauritania) and Cape Verga (Guinea Bissau). Although a latitudinal biodiversity pattern was not observed, preliminary results of R/V Dr. Fridtjof Nansen and Vizconde de Eza surveys recorded the highest diversity values in Western Sahara and also higher diversity on the shelf and upper slope than in deep waters. An important faunistic change between tropical and temperate biota has been reported at Cape Blanc latitude. The zoobenthos of Cape Verde and the Canary Islands shows some specific features linked to their volcanic origin, insularity and oceanographic conditions. Epibenthic communities maintain a similar structure throughout the region, despite the differences in their specific composition. Decapods seem to be the most important group, in terms of both abundance and biomass, being other representative taxa molluscs, echinoderms, sponges, cnidarians and polychaetes. Echinoderms, mainly holothuroids, are clearly dominant in deep waters. Suspension‐feeder assemblages, previously recorded in the entire upwelling area, do not seem to play an important role in the current epibenthic communities. Although tropical coral reefs have not been reported in NWA, vulnerable ecosystems, like the giant coldwater coral reef, canyon systems, seamount and grounds of sponges and gorgonians, still exist in deep waters of the continental slope, despite the intensive fishing exploitation over more than 50 years. Studies focused on these important vulnerable marine ecosystems, as well as on the currently unknown bottoms of deep‐shelf and slope (Senegal, Guinea‐Bissau, Guinea and Cape Verde), are strongly recommended in order to protect these deep‐water areas threatened by the trawling fleets’ displacement and by the oil and mineral resources exploitation. The assessment of the main benthic taxa during scientific and commercial demersal surveys would improve the ecosystem approach to marine resources management and also help keep track of changes in benthic biodiversity over time. Benthic research in regional marine scientific institutes should be promoted and strengthened and be considered as a highest priority line.