Approche combiné morphométrique et moléculaire pour la discrimination de trois espèces de Sparidés de la côte de Mostaganem

Abstract

This study aims to differentiate three species of the genus Diplodus, belonging to the family Sparidae (Diplodus sargus, Diplodus vulgaris, and Diplodus annularis), which are commonly found in the Mediterranean Sea, particularly along the Algerian coast. The high morphological similarity among these species makes their identification challenging when based only on external characteristics. To overcome this limitation, two complementary approaches were employed: a morphometric analysis of sagittal otoliths (88 pairs) and a phylogenetic study based on mitochondrial COI gene sequences retrieved from the NCBI database. In total, 140 individuals were collected between February and April 2025 in the Sidi Lakhdar region (Mostaganem). The average total lengths recorded were 14.79 ± 1.41 cm for D. annularis, 17.03 ± 3.93 cm for D. sargus, and 17.52 ± 2.11 cm for D. vulgaris. The average total weights were 59.33 ± 20.40 g for D. annularis, 108.60 ± 78.05 g for D. sargus, and 100.09 ± 34.43 g for D. vulgaris, respectively. Significant morphometric differences were observed between the species: D. sargus exhibited the largest and most elongated otoliths, whereas D. annularis was characterized by smaller and rounder otoliths. Shape indices (aspect ratio and roundness) confirmed these distinctions. Discriminant analysis and hierarchical clustering revealed a clear separation among the three species, particularly for D. sargus, while D. annularis and D. vulgaris showed a certain degree of morphological proximity. This classification was corroborated by the COI gene-based phylogenetic tree, highlighting a strong concordance between morphometric and molecular data. The findings confirm the taxonomic value of otoliths in the identification of sparid species. The combined approach developed in this study thus represents a relevant tool for fish taxonomy and may contribute to improved management of fishery resources, particularly in the context of artisanal fishing in Algeria.