Shape and symmetry in the otolith of two different species Mullus barbatus and Mullus surmuletus (Actinopterygii: Perciformes: Mullidae) in Tunisian waters

Abstract

Background. In Tunisian waters, there are only two mullet species, the red mullet, Mullus barbatus Linnaeus, 1758, and the striped red mullet, Mullus surmuletus Linnaeus, 1758. They are distributed along the coasts of eastern Atlantic from the North Sea to the northern part of West Africa. Therefore, M. barbatus and M. surmuletus are a valuable component of the commercial fishery in Tunisia. The goal of this study was to investigate the stock structure discrimination and otolith asymmetry for specimens of the mentioned above two species of the family Mullidae from waters of northern Tunisia. Materials and methods. We collected a total of 120 specimens of M. barbatus and M. surmuletus from Lac de Bizerte. The sampling was conducted within three months (March–April–May). The Elliptical Fourier Analysis (EFA) was performed to evaluate the degree of similarity in the otoliths and to determine the asymmetry percentage. Results. The Discriminant Factor Analysis shows significant results that are clearly demonstrated by an asymmetry when comparing otoliths (P < 0.05) within each population and a difference in shape when comparing the same side between the two species: between the two sides (right–right and left–left). Conclusion. The comparison of the otolith morphology of the two species showed a significant difference in shape and a left–right asymmetry of otoliths between and within populations. This result is probably related to genetic and local environmental factors. In fact, this investigation improves the knowledge of the stock discrimination for M. barbatus and M. surmuletus and provides useful information for analyzing fisheries management of these species in Tunisia.