The bathyal benthopelagic fauna in the north-western Ionian Sea: structure, patterns and interactions

The main knowledge acquired on the structure, patterns and interactions in the bathyal benthopelagic fauna in the north-western Ionian Sea is summarised in this article. Using faunal sampling along a depth range between 200 and 4000 m, a total of 41 cephalopods, 64 crustaceans and 183 fishes have been collected. Some are new findings for the study area and for many of the species the bathymetric distribution has been updated. Distinct faunal assemblages related to the upper slope (400-800 m), middle slope (8001200 m) and lower slope (>1200 m) were identified using Abundance Biomass Comparison curves. Species abundance decreases across the bathymetric gradient, whereas the biomass increases to similar to 1000 m and then decreases again. Beyond this bathymetry, species richness, evenness and diversity index decrease with depth. The distribution pattern 'bigger-deeper' was observed in some species and 'smaller-deeper' in others. Roccella canyon and the Santa Maria di Leuca coral bank were investigated in relation to the distribution of fauna, highlighting migration phenomena in the former and a refuge effect in the latter. The effects of hydrographic conditions and fishing were also examined for the deep-water commercial shrimps Aristaeomorpha foliacea and Aristeus antennatus.