Genetic structure and diversity of amphidromous sculpin in Shiretoko, a mountainous peninsula in Japan

Despite the global crisis facing migratory benthic fishes, conservation genetic knowledge of these species remains scarce. In this study, we conducted a population genetic analysis using seven microsatellite loci to obtain basic information for determining conservation units and priorities of Cottus hangiongensis in Shiretoko, a mountainous peninsula where sculpin habitats are thought to be in decline throughout the region. The genetic structure was clearly divided between west and east coastal populations, and there was little recent migration between them. The western populations, which are closer to the center of the species’ range, had significantly higher genetic diversity than the eastern populations. However, a bottleneck analysis and the inference of demographic history using approximate Bayesian computation showed that only the west group had experienced a significant recent bottleneck, probably due to recent habitat losses. These results suggest that the western and eastern populations should be different conservation units and that the western populations should be prioritized for conservation despite their high genetic diversity. This study contributes to the conservation genetics of diadromous sculpin and reiterates the importance of analyzing not only the current levels but also temporal changes in assessing genetic diversity.