Pattern of distribution and diversity of demersal assemblages in the central Mediterranean sea F. Colloca a, * , M. Cardinale b , A. Belluscio a , G. Ardizzone a a Department of Animal and Human Biology, University of Rome ‘La Sapienza’, V. le dell’Universita`, 32, 00185 Rome, Italy b Institute of Marine Research, National Board of Fisheries, P.O. Box 4, 45 332, Lysekil, Sweden Received 17 September 2001; received in revised form 29 November 2001; accepted 22 February 2002 Abstract A highly diversified mix of fish species, cephalopods and crustaceans, together with several macro-epibenthic organisms, compose trawl catches in the Mediterranean Sea. Management of Mediterranean trawling needs a multispecies approach that considers the community and not the single species as the basic unit of the analysis. While many studies have correlated several environmental factors to the spatial organizations of demersal organisms, few have focused on the role of macro-epibenthic communities in struc- turing demersal assemblages. In this paper, the following hypotheses were tested: (1) there are discrete demersal assemblages in the central Mediterranean Sea; (2) the distribution and diversity of demersal communities does not change on small temporal scales (1 year); (3) the demersal assemblages were segregated across both different epibenthic assemblages and depth gradients. Shallow sta- tions were separated into coastal and middle-deep shelf assemblages while stations on the slope formed three main assemblages: slope edge, upper slope and middle slope assemblages. The demersal community did not show a substantial change at the small temporal scale. Sandy, sand-muddy and detritic epibenthic communities characterized coastal shelf assemblages, while epibenthic assemblage on muddy bottoms were dominant in the deeper areas of the shelf. A well-defined difference in macro-epibenthic faunal associations among stations on the slope (depth > 200 m) was not found. Depth appeared to affect diversity of the main taxa of demersal organisms in different ways. Teleostean diversity did not show any trend with depth, the number of cephalopod species increased on the shelf and decreased on the slope while crustacean and elasmobranch species richness increased significantly from the shelf to the middle slope. The strong correlation shown in this study between epifaunal benthic communities and demersal fish assemblages requires the formulation of an ecosystem-based management for the Mediterranean Sea trawl fisheries. The existence of such biological diversity certainly contributes to the Mediterranean ecosystem health and its conservation should become one of the main objective of demersal resources management in the future. Ó 2003 Elsevier Science B.V. All rights reserved. Keywords: Mediterranean sea; assemblages structure; fauna distribution; macrobenthos; diversity 1. Introduction Bottom grounds of Mediterranean Sea are intensively trawled for commercial fishing at depths ranging from 50 to 700 m (Farrugio, Oliver, & Biagi, 1993). Trawl catches are composed of a highly diversified mix of fish (teleosteans and elasmobranchs), cephalopods and crus- taceans (decapoda and stomatopoda), together with sev- eral epifaunal macrobenthic species (Relini, Bertrand, & Zamboni, 1999). In relation to these characteristics, management of Mediterranean trawling should require a multispecies approach, which considers the commu- nity (i.e. assemblage sensu Tyler, Gabriel, & Overholtz, 1982) and not the single species as the basic unit of the analysis. The traditional approach, based on single stock assessment, represents an inadequate management strategy for such multispecies fishery because it does not consider the effect of interspecific relationships on the species abundance and distribution (Pitcher, 2000). In this context, information on species distribution is fun- damental to identify those strategies that may optimize the catch of a group of species and, thus, improve their * Corresponding author. E-mail address: francesco.colloca@uniromal.it (F. Colloca). Estuarine, Coastal and Shelf Science 56 (2003) 469–480 0272-7714/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0272-7714(02)00196-8