The use of Fourier analysis as a tool for Oblada melanura (Linnaeus, 1758) stock unit separation in the south central Mediterranean Sea

For the first time, an otolith shape analysis was used to investigate the stocks of saddled bream (Oblada melanura, Linnaeus, 1758) in three fishing zones along the Tunisian coast (Bizerte, Kélibia and Sayada). Otolith shape analysis was used on 30 otoliths for each site, sampled during the spawning period. Using elliptic Fourier descriptors (EFD) the quantization of the shape otolith was investigated by SHAPE and multivariate statistical procedures. Considering the environmental and the genotypic aspects, the preliminary results of the otolith shape analysis showed dissimilarity in silhouette of otoliths of saddled bream stocks collected from the north (Bizerte), the north-east (Kélibia) and the east (Sayada) of the Tunisian coast. Therefore, these three groups could be considered as three sub-units of the Tunisian stock, which should be managed separately.