Phylogeography of yellowfin tuna ( Thunnus albacares) in the Western Pacific and the Western Indian Oceans inferred from mitochondrial DNA

Yellowfin tuna ( Thunnus albacares) is a highly migratory cosmopolitan fish inhabiting most tropical and subtropical waters between 40°N and 40°S. It is an important commercial species in the world fisheries. In the present study, population structures of yellowfin tuna in the Western Pacific Ocean and the Western Indian Ocean were investigated using mitochondrial DNA sequence data analysis. A total of 124 individuals were sampled from Taiwan of the Western Pacific Ocean ( n = 73) and Seychelles of the Western Indian Ocean ( n = 51) and among them, 111 haplotypes were revealed. Both high levels of mitochondrial control region haplotypic and nucleotide diversities were observed in both the Western Pacific and the Western Indian populations. The reconstructed neighbor-joining tree based on the Kimura two-parameter model indicated that one phylogroup of yellowfin tuna existed in the Western Pacific and the Western Indian Oceans. Non-significant pairwise F ST values revealed extensive gene flow between yellowfin tuna populations from the Western Pacific and the Western Indian Oceans. Our mitochondrial DNA results suggested that yellowfin tuna in the Western Pacific and the Western Indian Oceans exhibits no genetic differentiation in geographic distributions.