Stock discrimination of two insular populations of Diplodus annularis (Actinopterygii: Perciformes: Sparidae) along the coast of Tunisia by analysis of otolith shape

The annular seabream, Diplodus annularis, is the most common sparid fish in the Mediterranean Sea. This species is widespread in Tunisia. Despite their economic importance, due to their excellent white and delicate flesh (demersal fish) and their significant size, few studies have hitherto focused on stock discrimination and on the fisheries management. The goal of this research was to evaluate the stock structure of D. annularis for two Tunisian insular populations based on the otolith shape, using different statistical approaches. The specimens of Diplodus annularis were collected during five months ranging from May through September 2014 at two sites: Djerba and Kerkennah. By comparing the two studied populations, the authors revealed statistical significant differences, an asymmetry (left-right), of otoliths (P < 0.05). In the same population, symmetry (left-right) was detected for the males, females of Kerkennah, and females of Djerba. However, an asymmetry was detected only for the males of Djerba. Also, sexual dimorphism was observed only for the Djerba population.