Comparison of demersal fish assemblages in three areas of the Strait of Sicily under different trawling pressure

The effect of trawling on demersal fish assemblages was measured in an experiment involving repeated trawling in the Strait of Sicily. Three areas were chosen according to their exploitation level by commercial trawl fishery: practically unexploited by the commercial fishery (area C), subject to light and recent fishing pressure (area L) and heavily exploited by commercial trawl fishery (area H). Data were collected during two scientific surveys carried out in autumn 1997 and 1998; temporal replication was used to confirm the observed spatial pattern. The status of the demersal fish communities in the three areas was compared using a variety of approaches and a number of community metrics (cluster analysis, similarity percentage analysis, ANOSIM pairwise test, size spectra, diversity indices). Results indicate that abundance, species composition and size-structure of the fish community in area H are different from the other two areas. Differences between area C and area L are small and concern mainly the relative abundance of some species. Eventually, the results show how fishing can substantially shape the fish communities in the three areas.