Discrimination between six commercially relevant and ecologically diverse fish species across the Gulf of Tunis using fatty acid composition and otolith shape analyses

: Fatty acid composition and otolith shape variation of six commercially important fishes, which differ ecologically in their living and feeding habits across the Gulf of Tunis, Tunisia, were analyzed. The aims were to investigate the discrimination and relationship between the six species using both fatty acid composition and otolith shape to examine whether variability in fatty acid composition is consistent with variation in otolith shape and check whether otoliths shape and fatty acids composition have combined characteristic signals for these species. Tukey’s test with one-way ANOVA indicated significant differences in total percentages of saturated (SFAs), polyunsaturated (PUFAs), and monounsaturated (MUFAs) fatty acids between individuals of the six species, and only between males and females of Gobius niger , and Trachinus draco . Discriminant function analysis (DFA) separated the six species into two main distinct clusters or groups. The first group comprised Mullus barbatus , G . niger , and T . draco , which assume a benthic life, while the second included Sardina pilchardus , Trachurus mediterraneus, and Chelon auratus , which are benthopelagic to pelagic species. Wilk’s λ test and Fisher’s distance ( D ) matrix showed a significant bilateral asymmetry in the left and right otoliths shape between individuals of the six species, as well as only between males and females of C . auratus , T . mediterraneus , and G . niger . However, a significant bilateral asymmetry was found only between females of G . niger and males of T . draco . DFA and hierarchical ascending classification (HAC) based on otolith shape variance revealed two main groups of otoliths congruent to those obtained from fatty acid composition analysis. The results indicated that fatty acid composition analysis was compatible with otolith shape analysis, and both have combined characteristic signals for these species and validated the use of fatty acid composition and otolith shape analyses as an effective approach to discriminate between and within these species.