A high level of genetic diversity was observed in Katsuwonus pelamis populations from India (h ¼ 0Á952, ne ¼ 14Á3) and Japan (h ¼ 0Á897, ne ¼ 8Á9). The log-likelihood (G)-based exact test revealed significant heterogeneity in the distribution of haplotypes between the two populations (P < 0Á01, S.E. ¼ 0Á001). This result suggests that the two populations should now be treated as demographically independent and managed separately. #

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Genetic structure of skipjack tuna Katsuwonus pelamis from the Indian region was investigated using sequence data of mitochondrial DNA (mtDNA) D-loop region. A total of 315 individuals were sampled from six major fishing grounds around the east and west coasts of India including the Andaman (Port Blair) and Lakshadweep (Minicoy) Islands. Nucleotide and gene diversities were high in all the sample collections. Significant genetic heterogeneity was observed for the mtDNA sequence data among sites (φ(ST) = 0·0273, P < 0·001). Analysis of molecular variance (AMOVA) showed significant genetic variation among four groups (φ(CT) = 0·0261, P < 0·05) which was also supported by spatial AMOVA results. The null hypothesis of single panmictic population of K. pelamis along the Indian coast can thus be rejected. Phylogenetic analysis of the mtDNA sequence data showed the presence of four clades of K. pelamis in the Indian waters. There was no clear pattern, however, of haplotypes and geographic location among samples. The results of this study suggest the occurrence of four genetically differentiated groups of K. pelamis across the coastal waters of India.

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