Abstract:The worldwide climate and marine environmental changes have significant impacts on the distributions and fishery resources abundance fluctuations of Dosidicus gigas in the East Pacific Ocean.It is important to investigate genetic variance and population genetic structure of D.gigas in order to exploit and manage this squid scientifically.In this study,the genetic diversity and the genetic differentiation between two geographical populations of D.gigas were analyzed based on two mitochondrial DNA molecular markers.The results showed that the number of haplotype,haplotype diversities,nucleotide diversities and average nucleotide differences were 7,(0.397±0.079),(0.001 09±0.000 96) and 0.600 respectively in all Cytb sequences of two geographical populations,and haplotype diversity in population off the coast of Peru was only(0.282±0.101)which was significantly lower than that of equatorial waters.On the other hand,the number of haplotype,haplotype diversities,nucleotide diversities and average nucleotide differences in all COⅠ sequences were 17,(0.787±0.051),(0.002 90±0.001 38)and 1.802 respectively.The pairwise fixation index Fst and median network revealed lack of genetic structure between populations of equatorial waters and off the coast of Peru(Cytb:Fst=0.055 23,P>0.05;COⅠ:Fst=0.005 91,P>0.05),and this might be caused by equational oceanographic current.The minimum spanning network tree,mismatch distribution analysis and neutrality tests suggested that D.gigas experienced a recent population expansion,possibly 138 900 to 167 900 years ago.