Demersal Fauna on Deep Seamounts of Sierra Leone Rise (Gulf of Guinea, Africa)

Abstract

From January to March 2001 an experimental fishing survey was carried out on the Sierra Leone Rise by four Spanish commercial boats, with the aim of prospecting the fishing potential for longliners of the demersal resources inhabiting the seamounts located between 9ºN-5ºN and 19ºW-27ºW, at depths between 200 m and 1 000 m. A preliminary analysis of the data recorded shows that the demersal fish fauna composition was similar in three of the ten seamounts, with an absolute dominance of the alfonsino, Beryx splendens Lowe, 1838, which accounted for more than 90% of the total catch between 200 and 800 m depth. Other commercial species in catches were Beryx decadacthylus and some Scorpenidae. The size structure and the distribution of alfonsino oscillated between 27 and 52 cm showing an increase of the mean size with depth which is similar to the pattern found in other seamounts worldwide Major abundances were located at the northern surveyed seamount where the highest yields, up to 750 kg per 1 000 hooks, were obtained. The southernmost surveyed seamount exhibited the lowest abundances and was characterized by the absence of the alfonsino in the catches. The species richness of these deep communities was very low, the accompanying fauna comprising less than 30 species. Discarded fishes were, in order of abundance: Promethicthys prometeus, Coloconger cadenati, Polymixia nobilis, Ruvettus pretiosus, Etmopterus princeps, Serranus accraensis and Gephyroberyx darwini