A spatial analysis of the commercial fisheries catches from the Greek Aegean Sea

Abstract

In the present study, univariate (number of species, species diversity, eveness, richness) and multivariate analysis techniques (cluster analysis and multidimensional scaling) are used, together with dominance curves, to describe the major biogeographical features of the demersal and pelagic fisheries in ten Greek statistical fishing subareas of the Aegean Sea for the years 1982–1987, inclusive. The results from the various statistical techniques applied were in close agreement and all suggested that the ten statistical fishing subareas could be generally grouped into three main areas (northern, central and southern Aegean Sea) for the pelagic fishery and into two main areas (northern and southern Aegean Sea) for the demersal fishery, which differed considerably from each other in terms of species composition, species diversity and catch density (catch weight per unit area). In general, with respect to the pelagic fisheries, the catches from the northern, central and southern Aegean area groupings are dominated, respectively, by anchovy ( Engraulis encrasicolus (L.), 48.2%), horse mackerels ( Trachurus spp., 23.2%) and bogue ( Boops boops (L.), 40.6%). For the demersal fisheries, the catches from the northern and southern Aegean area groupings are dominated by grey mullets (Mugilidae, 10.3%) and pickerel ( Spicara smaris (L.), 28.6%), respectively. The main factors which appear to be contributing to this geographical group differentiation are: (a) the gradient in the relative eutrophy, river runoff, temperature and salinity of the Aegean Sea waters along a NNW to SSE axis; and (b) the differences in extent of the continental shelf within these areas of the Aegean Sea. The managerial implications of the results of these spatial analyses are discussed and emphasis is given to the experimental establishment of marine harvest refugia which provide a refuge for fish populations in space, rather than the ‘refuge in numbers’ which has been the basis of most traditional fisheries management measures so far applied in this area.