The Use of Sagittal Otolith Shape Analysis in Discriminating of Four Carangidae Species from the Persian Gulf

The sagittal otolith’s contours were studied to discriminate between four Carangid species including Carangoides coeruleopinnatus, Carangoides chrysophrys, Carangoides malabaricus, and Megalaspis cordyla from the Persian Gulf. After preparing Sagittal otolith photos, their contours were analysed by elliptic Fourier analysis using Shape software. The chain codes, harmonics and elliptic Fourier coefficients were obtained for each sample. The mean otolith contours values were rebuilt by specific values. The shapes of otoliths were studied by elliptic Fourier descriptors of 20 harmonics and 6 shape indices. These four species were discriminated successfully using shape indices (72.2%), elliptic Fourier coefficients (73.7%), or combination of both techniques (72.2%). No classification success was achieved in discriminant analysis using merely shape indices. The results of principal components analysis (PCA) also indicated that the percentage of variance in the first principal component of each species showed maximum value and the principal components were reduced respectively. However, cumulative variance showed how the estimated shape by elliptical Fourier transformation can represent the corresponded species shape. The results of this study show that combining the size according to shape descriptors and EFD is a suitable tool to distinguish of four Carangid species.