Microsatellite DNA polymorphism of Japanese sea bass (Laterolabrax japonicus) inhabiting Chinese and Japanese coasts

Twenty-two microsatellite DNA markers were developed for Japanese sea bass (Laterolabrax japonicus), of which 19 were independent from each other and at Hardy-Weinberg equilibrium across the three populations of Japanese sea bass inhabiting Chinese coasts (defined as China group) and the five populations inhabiting Japanese coasts (defined as Japan group). These 19 markers were used to determine the number of alleles and the expected heterozygosity across the eight populations. The majority of individuals (93.8-98.8%) of the three populations of the pre-defined China group were assigned to an inferred cluster, and 90.9-94.6% of the individuals of the five populations of the pre-defined Japan group were assigned to the other. The average number of alleles across the 19 loci was significantly lower in the China group than in the Japan group (10.3 vs 15.4), however, the average expected heterozygosity across the 19 loci of the China group was similar to that of the Japan group (0.743 vs 0.750). An effective population size reduction (i.e. bottleneck effect) was detected in the China group (P = 0.00357), which may have resulted from either over-catching or glaciations or both. The pairwise F-ST among populations of the China group (0.019-0.029) and among populations of the Japan group (0.003-0.021) were lower than those between the populations of the China group and the populations of the Japan group (0.076-0.101). The average pair-wise F-ST between the populations of the China group and those of the Japan group reached 0.075, and the variation between the China group and the Japan group accounted for 7.16% of the total. Nei's original measures of genetic distances among the populations of the China group and the Japan group ranged from 0.123 to 0.145 and from 0.055 to 0.123, respectively, while that between the populations of the China group and the populations of the Japan group ranged from 0.326 to 0.450. Japanese sea bass is able to disperse over a long distance; however, our observations demonstrated that it cannot migrate across a possible barrier existing between Chinese and Japanese coasts. Most individuals of the Zhoushan population of the China group were assigned to two inferred clusters, and most individuals of Ariake Sea, Tokyo Bay and Ishikawa populations of the Japan group were assigned to three inferred clusters, indicating that these locations were the gathering grounds of Japanese sea bass.