Localisation of spawning and nursery areas of Red mullet (Mullus barbatus, Linnaeus) in the Italian side of the Strait of Sicily (Central Mediterranean)

Knowledge of the location of spawning and nursery grounds represents crucial information for the management of resources, where an 'input control approach' is applied, as is the case in the Mediterranean. Red mullet, Mullus barbatus, is one of the most important demersal resources in the Mediterranean, being mainly caught by bottom trawling on continental shelves. A space-time analysis within a Geographic Information System (GIS) was performed in order to identify and characterize the spawning and nursery areas of red mullet on the Italian side of the Strait of Sicily. Annual indices of spawner and recruit densities per square kilometer (N/km2) were estimated from trawl surveys carried out in the Strait of Sicily both in six spawning seasons (spring) and nine recruitment seasons (autumn). Spawner and recruit densities were normalised to the highest observed survey index in order to reduce differences due to interannual variability. Distribution maps were produced by kriging interpolation. Statistics were computed for the temporal series of maps, including a map similarity index. Results showed patchy and spatially distinct distributions of both spawners and recruits, reflecting changes in the species' habitat preferences during its life-cycle. Two major, clearly separate, spawning grounds exist in the area, both at around 100 m depth. The recruits were rather widely distributed throughout Sicilian coastal waters. Nevertheless, four areas of high concentrations were identified, between 20 m and 50 m depth, which were quite stable in location. These results, even if preliminary, provide baseline information for advice on seasonal closures to trawling, aimed at improving the exploitation pattern of the overfished stock in the area.