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Summary Genetic stock structure is atypical in tuna species, with most species demonstrating geographically-broad, panmictic populations. Here, genetic data suggest a distinct pattern for Thunnus tonggol across the Indo-Pacific region. The genetic variation in the coastal tuna T. tonggol sampled from across the South China Sea was examined using the highly variable mitochondrial DNA displacement loop (D-loop) gene region. One hundred and thirty-nine specimens were sampled from four locations in Indonesia, Vietnam and the Philippines. Phylogenetic reconstruction of genetic relationships revealed no significant ɸST statistics and hence no population structure within the South China Sea. However, subsequent analysis with sequence data from coastal northwest India infers discrete genetic stocks between the Indian Ocean and the South China Sea. Consistent with previous genetic analyses of tuna species in the Indo-Pacific, the findings in this study infer no population structure within each basin, but rather show a significant partitioning across the wider region. Furthermore, these results have implications for the management of the commercially valuable Thunnus tonggol across national boundaries, and thus requiring collaboration among countries to ensure its sustainable use.

Summary Morphology, meristics, and molecular genetics tools were used to determine the species level identification of the most commonly landed sardine species in the Philippines. Results from this study indicated that the historical and widely applied nomenclature of the Indian oil sardine, Sardinella longiceps, is incorrect and that this species is instead the Bali sardinella Sardinella lemuru. Developing an effective strategy for managing one of the Philippines most important commodity sardine species first requires accurate identification of this species. Results of this study provide needed information that is now being applied to emerging management policies.