RFLP analysis of the mtDNA D-loop region in red sea bream Pagrus major population from four locations of western Japan

The magnitude of intraspecific genetic differentiation of red sea bream Pagrus major collected from four areas of western Japan, was estimated using restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA) D-loop region. Sixty-one composite haplotypes, representing information from 6 restriction endonucleases, were generated for samples of 38-58 fish from each site in 1994, and 72-95 fish from each site in 1995 from Tanabe Bay, Tomogashima Suido, Bingo Nada, and the Japan Sea. Genetic variation was relatively high in all samples: the haplotypic diversity was 0.86-0.90 in 1994 and 0.88-0.92 in 1995, and the averages of the mean nucleotide sequence divergence between and within samples were 0.99 and 0.99%, respectively. On the contrary, the pure mean nucleotide sequence divergence between samples is low, 0.01% in average. Significant heterogeneity was not observed in the distribution of haplotypes among samples both in 1994 and 1995. Furthermore, significant differences were not observed in 23 pairs of 28 combinations of 8 samples. Consequently, differences among samples of red sea bream are not so large basically, although significant geographic differences were observed between Bingo Nada where the genetic structure may be unstable and Tanabe Bay where many hatchery released fishes were caught together with the natural fishes.