| 英文摘要 |
Bigeye tuna are of great commercial importance, and their catches comprised about 15% (15 billion Taiwanese yens) of the total fishery productivity in Taiwan. A thorough understanding of the bigeye tuna population structure is necessary for the effective management of this highly migratory marine species, but our knowledge on this subject is still very limited. The main objective of this proposed study is to elucidate the existence of these bigeye tuna population stocks inferred from mtDNA control region polymorphisms. Tissue samples of bigeye tuna will be collected mainly from Western Pacific, central Pacific and eastern Pacific oceans. At first, the sequence polymorphisms of the mtDNA control region of the tuna will be analyzed to determine their genetic clade as described above. The results should provide insights of the population stocks of bigeye tuna, which will help the management and conservation of this important commercial species. The population structure of bigeye tuna (Thunnus obesus) in the Pacific Ocean was investigated using sequence data of the first hypervariable region (HVR-1) of the mitochondrial control region. A total of 426 specimens were sampled from two regions in the Central Pacific Ocean, one in the Western Pacific Ocean and Eastern Pacific Ocean, respectively. Nucleotide diversities (from 0.036 in Eastern Pacific to 0.045 in Central Pacific) and haplotypic diversities (from 0.975 in Central Pacific to 1.000 in Eastern Pacific) were high in all sampling locations. The reconstructed neighbor-joining tree showed that the haplotypes from Central and Western Pacific Oceans can be grouped into two clades (Clade I and III) whereas two divergent clades (Clade I and II) coexist in the Atlantic Ocean. Clade I is the major group which consists of more than 97 % of the specimens in each Pacific population and Clade II is a specific group exclusive to the Atlantic Ocean. Analyses of mtDNA control region sequences revealed lower, non-significant genetic differentiation between regional populations (FST =0.001～0.015). Furthermore, all analyses indicate that bigeye tuna over the sampling area constitute a single panmictic population. |