FISH ASSEMBLAGES ON THE SLOPE IN THE CATALAN SEA (WESTERN MEDITERRANEAN) - INFLUENCE OF A SUBMARINE-CANYON

The analysis of 35 bottom trawls taken on the slope in the Catalan Sea (western Mediterranean) has shown the existence of two different deme rsal fish assemblages occurring on the upper (350-650 m) and middle (1 150-1300 m) slope. The middle slope assemblage is characterized by muc h higher values in some ecological parameters such biomass and mean fi sh weight, resulting from the dominance of middle to large size specie s (e.g. Alepocephalus rostratus, Trachyrhynchus trachyrhynchus, Mora m oro). On the upper slope two different stations were considered, one i nside and the other outside a submarine canyon. Only slight difference s were found in species composition, and hence sample and species were not clearly separated by a correspondence analysis. However, some int eresting ecological differences exist between these two stations. Much higher values in abundance and biomass inside the canyon were indicat ive of higher food availability there. Moreover, a drop in mean fish w eight was also noted inside the canyon. The analysis of size distribut ions in the commonest species along the upper slope showed that the su bmarine canyon acts as a recruiting ground for some of them.