Variations in the trawl catch compositions in the Aegean sea

In this study, bottom-trawl catch data collected from the Aegean Sea between July 1991 and August 1995 were analysed. The Aegean Sea is divided to five main regions according to its ecological properties, and trawl samples from each region were grouped by these sub regions in the basis of depth and season. The biomass of each species (t/km2) for each sub region were calculated. Although the total biomass estimates according to sub regions were highly variable ranging from 0.22 to 8.75 tonnes, in general similar biomass distribution patterns were observed. Diversity and evenness index were calculated and similarities between each trawl catch compositions were checked by cluster analysis. While the species diversity of northern Aegean Sea, were higher than southern Agean, the highest values were estimated in the regions of I and II. Depth is found as a main factor affecting the trawl catch compositions. Seasonal and regional variations were not found a determinative effect on the catch compositons.