Population structure of albacore (Thunnus alalunga) in the Northwestern Pacific Ocean inferred from mitochondrial DNA

Albacore (Thunnus alalunga) is a highly migratory cosmopolitan fish commonly distributed throughout all oceans. It is an important commercial species in the world fisheries. In the present study, population structure of albacore in the Northwestern Pacific Ocean was investigated using mitochondrial DNA sequence data analysis. A total of 175 individuals were sampled from three regions in the Northwestern Pacific Ocean (Taiwan, Japan and North of Hawaii) and among them, 168 haplotypes were revealed. Nucleotide diversities and haplotypic diversities were high in all sampling regions. The reconstructed neighbor-joining tree based on the Kimura two-parameter model indicated that two clades of albacore coexisted in the Northwestern Pacific Ocean. Clade I is the main clade consisting of 98% of the total specimens and is further divided into two lineages (Lineages I and II). Hierarchical AMOVA tests and pairwise ΦST analysis showed that albacore tuna in the Northwestern Pacific Ocean constituted a single stock with no significant differences in geographic distributions.