The genetic diversity of wild and hatchery-released Pacific herring Clupea pallasii collected from three brackish lakes and two bays in Honshu and Hokkaido, Japan was examined with five microsatellite loci. All loci showed high genetic variability with expected heterozygosities ranging from 0.815 to 0.945. Significant differences in genotypic and allelic distributions were detected among all locations except for between the two bays in Honshu Island. Pairwise population analysis based on the FST values showed close genetic relationships among the locations in Hokkaido Island, and the hierarchical analyses of molecular variance showed significant genetic difference between the two islands. Those results suggest the existence of subpopulations due to natal homing. In addition, stocked fish showed as much genetic diversity as the wild fish. The pairwise population analyses also showed close relationships between the hatchery fish and the wild fish in respective stocking areas, showing that no effects of stocking programs on genetic diversity of wild populations were detected.

fidelity creates weak but significantly differentiated stable population structure. This process can allow restoration of the genetic characteristics of damaged populations over many generations and can thereby promote the long-term viability of marine fishes that have high gene flow.

Using the mitochondrial DNA control region sequences of 549 bp for 618 Paciˆc herring from 16 spatiotemporal samples collected at nine spawning sites in the Hokkaido and Tohoku areas of Japan during the spawning period between 2003 and 2014, we estimated the contemporary population structure and demographic history of the Japanese herring. Neighbor-joining unrooted phylogenetic trees based on the empirical Bayes pairwise F ST values showed three large clusters consisting of six local samples in Hokkaido, Lake Obuchi-numa, and Miyako Bay/Matsushima Bay in Tohoku. Hokkaido samples had higher genetic diversity than Honshu samples. The haplotype frequency of Miyako Bay after the Great Tohoku earthquake was substantially diŠerent to that before the earthquake, but similar to that of Lake Obuchi-numa. Our demographic analyses inferred that the eŠective population size (N e ) has expanded since at least ～600 kyr ago in Hokkaido but is stable in Honshu, but a rapid and simultaneous decrease in N e has occurred since ～20 kyr ago in Japanese herring, corresponding to the warming after the Last Glacial Maximum.

Japanese Spanish mackerel Scomberomorus niphonius is a target species for stocking, but 18 their biological characteristics at the juvenile stage are not well understood. Here, we 19 investigated the high-temperature and starvation tolerances of hatchery-reared juveniles in 20 captivity. We used juveniles of approximately 40 mm standard length, which was the size of 21 the juveniles released into the field. The upper incipient lethal temperature (50% lethal water 22 temperature) was estimated to be 31.8 °C, which was higher than the maximum sea surface 23 temperature in the field (approximately 29 °C). The critical thermal maximum was 34.8 °C, 24 whereas it was 36.1 °C when juveniles were preliminarily acclimated to 31 °C for 24 h.

Population structure and demographic history of Paciˆc herring Clupea pallasii around Japan inferred from mitochondrial DNA sequences a Tel81 3 5463 0536．Fax81 3 5463 0536．Emailkitada＠kaiyodai.ac.jp b 現所属(公社)全国豊かな海づくり推進協会 図 1 日本産ニシンの遺伝的集団構(原著の結果から作 図) 4)