Population genetics of tunas in South China Sea inferred from control regions

The South China Sea(SCS)surrounded by the first island chain is a semi-enclosed sea linking the Indian Ocean and the Pacific Ocean.The population genetic features of the two most important economic species,yellowfin tuna(YFT,Thunnus albacares,17 adults and 44 juveniles)and big eye tuna(BET,T.obesus,22 adults and 4 juveniles)in SCS(11-12?N,15?N;110-112?E),have been analyzed based on the partial mitochondrial D-loop sequences.Our data supported the following conclusions:(1) both species were high nucleotide variation with very high haplotype diversities(H_d＞99%),while the evidence from fixation indexes,and cluster trees showed the population diversity of BET was higher than those of YFT;(2) For BET and YFT,the strongest gene flow between populations in SCS and the Indian Ocean were 51.638 and 261.280 10,then the Pacific by 10.868 8 and -50.801 81,respectively;(3) both species obey the sudden expansion model.Contrasted with the unimodal of YFT,the mismatch distribution of BET,as well as the SCS population,were bimodal.Moreover,the spanning time of SCS population of BET was later inferred from the T_au(=7.902)with biggest spanning scale(θ₁/θ₀=99 999/14.752).The results should be basic information for fisheries management,fishing quotas determination as well for aquaculture of tuna.