On the basis of morphoanatomical parameters, the sand smelt species (Atherina boyeri Risso, 1810) is viewed as a highly polymorphic complex. In this study, intraspecific sequence variation in a portion of the cytochrome b gene was examined in 88 individuals from Tunisia and France. The correlation between the results of statistical analysis of the sequence data using a variety of tree-building algorithms and morphoanatomical analyses demonstrated the subdivision into three putative species: A. boyeri, which only includes non-punctuated fishes, A. punctata, which corresponds to punctuated fishes and A. lagunae, which corresponds to atherines living in lagoons.

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Background. The annular seabream, Diplodus annularis (Linnaeus, 1758), is the most common sparid fi sh in the Mediterranean Sea. This species is widespread in Tunisia. Despite their economic importance, due to their excellent white and delicate fl esh (demersal fi sh) and their signifi cant size, few studies have hitherto focused on stock discrimination and on the fi sheries 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. Materials and methods. The specimens of Diplodus annularis were collected during fi ve months ranging from May through September 2014 at two sites: Djerba and Kerkennah. In total, 120 fi sh were collected from the two sites: 60 specimens of each population (30 males and 30 females) and were included in different statistical analyses. The Fourier coeffi cients were determined to evaluate the degree of similarity in the otoliths and detect the reciprocal variability. Results. By comparing the two studied populations, we revealed statistical signifi cant 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. Conclusion. The comparison of the otolith morphology of the two populations showed a clear difference in shape and a left-right asymmetry of otoliths. This asymmetry indicates that the two populations belong to different stock of fi sh. The stocks characterization is considered as an important tool for fi sheries management. Further studies are necessary to determine the origin of the otolith shape differences and whether they are related only to environmental conditions or a genetic basis may also be responsible.