Otolith chemistry suggests population heterogeneity within a genetically homogeneous Indian scad population along Indian coast.

The Indian scad, Decapterus russelli is one of the most exploited pelagic resources of India. Population genetic analyses using mitochondrial and nuclear markers indicated a lack of genetic structuring among populations from Indian waters. As this species is highly migratory, it is also important to establish the environmental influence on its population structure. In the present study, the whole sagittal otolith composition was analysed using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) to assess spatial distribution of D. russelli collected from 4 sites along the Indian coast. Elemental ratios (Ba/Ca, Fe/Ca, K/Ca, Mg/Ca, Na/Ca, Sr/Ca and Zn/Ca) were analysed using univariate and multivariate statistics to determine whether this chemical signature can provide insight into the adaptive patterns. All element/Ca ratios are found to be significantly different between the four sampling locations (ANOVA, p < 0.05; MANOVA, p < 0.05). Five of the element/Ca ratios were found to be significantly different when the data was analysed coastwise (ANOVA, p < 0.05; MANOVA, p < 0.05). The LDA plot also showed the spatial heterogeneity of Element/Ca ratios between the four sampling sites, but some overlaps were also observed, reflecting the migratory ability of the species. This basic information on spatial ecology is required for formulating effective management and conservation strategies for the species.