biogeography of epibenthic crustaceans on the shelf and upper slope off the iberian peninsula mediterranean coasts: implications for the establishment of natural management areas

The patterns of occurrence and bathymetric distribution of epibenthic crustaceans on the continental shelf and upper slope down to a depth of 800 m are analysed based on data gathered during six demersal trawl surveys performed annually in spring along the Mediterranean coasts of the Iberian Peninsula (from the Straits of Gibraltar to Cape Creus) between 1994 and 1999. A total of 598 valid hauls has been studied providing a total of 108 species of decapods, two stomatopods, one euphausiid, one mysid and one isopod. The study area has been subdivided into seven sectors according to their geomorphological characteristics, and the patterns of occurrence and abundance by depth have been analysed separately for each of the sectors. Detailed data on bathymetric distribution are presented for each species. Two main biogeographical areas can be discerned along the study area, which can approximately be separated at Palos Cape: the Alborán Sea to the southwest, and the northwestern Mediterranean (Levantine and Catalan Seas) northwest of Palos Cape. The continental shelf in the Alborán Sea (the most western area of the Mediterranean) is extremely narrow whereas it is much wider in the northwestern Mediterranean. The influence of Atlantic waters entering the Mediterranean is particularly strong in the Alborán Sea which shows a particularly high species richness of Atlantic affinity. Within the context of the western Mediterranean Sea, the Alborán Sea region shows important faunistic characteristics such that it might be considered as a possible separate natural management area for demersal fisheries.