Evaluation of fish fauna of Monaco's submarine nature reserve

The aim of this study was to evaluate the fish populations inhabiting various biotopes of the Monaco submarine nature reserve. These biotopes, ranging in depth from 0 to 40 m and including several artificial reefs, were evaluated visually by SCUBA diving. This method is of proven reliability. Three fixed stations (on the reefs) and three transects (pier, sea wall and Posidonia bed) were analyzed each season. The fixed stations corresponded to 80 m super(2) circles. The transects corresponded to "tunnels" of 10 m width and 5 m height. A 50 m transect corresponds to about three 900-m super(3) of water. The results have permitted the calculation of the species diversity, fish densities and biomass, as well as a distribution index for each sampling zone. Down to a depth of 20 m, the marine reserve has a high density of fish but a low species diversity (the most abundant species are Chromis chromis and Spicara maena). The Posidonia beds contain low numbers of fish (0.1-2.1 fish/m super(2), biomass = 2-25 g/m super(2)) and a low species diversity (6). The total fish density on the rocks of the piers was 6.34/m super(2) equal to 107.6 fish/linear m of pier (39.7 fish/m if Chromis is excluded, and a total biomass of 2,138 g/linear m or 126 g/m super(2)). Diplodus sargus was the most abundant of the 29 species of fish encountered in this biotope. All of the size classes of this fish were present. The reefs, composed of stone blocks ( approximately 100 m super(2) and 100 m super(3)) and situated at 20-30 m depth, showed the highest biomass of fish (90-212 g/m super(2)), whilst built reefs (