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Background: Pacific bluefin tuna (Thunnus orientalis) spawning adults, juveniles and larvae are all reported to occur in areas between Philippine Sea and Japan Sea. However, no DNA evidence has been generated to support this. Context and purpose of the study: In this study, Pacific bluefin tuna caught North of Polilio Island in the Philippine Pacific Seaboard, was identified through DNA barcoding using mitochondrial DNA D-loop region and cytochrome oxidase 1 gene. Findings: The results show clustering of Philippine-caught bluefin tuna D-loop and CO1 sequences with published reference sequences for T. orientalis and supported by pairwise distances <0.034. Conclusion: This study provides the first DNA evidence on the occurrence of T. orientalis in Philippine waters. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the natal origin of Pacific bluefin tuna Thunnus orientalis inferred from otolith oxygen isotope composition. The study demonstrated that otolith oxygen isotope values varied from -2.5 to -2.2% between the otolith core for age-0 tuna caught in the Japan Sea, while those caught in the Pacific Ocean varied between -2.8 and-2.2%. It was also observed that the temporal difference in experienced water temperatures produces an earlier increase of otolith oxygen isotope values for tuna caught in the Japan Sea than in the Pacific Ocean.