Abstract
Population genetic structure of a common freshwater goby Rhinogobius fluviatilis in the Yoshino River and its tributaries was surveyed using three microsatellite loci to examine effects of dams. Allelic richness of the Akui and Sadamitsu River populations below the dams were high (15. 7, 15. 9) and that of the above the dams populations were low (10. 9～13. 0). Heterozygosity was same level diversity between above and below dam populations (0. 870～0. 890) except for Takeno river population (0. 788). Considerable genetic differences were observed between populations above and below the dams. Migratory history was also examined using otolith Sr/Ca ratio. The otolith Sr/Ca ratio analysis confirmed that the populations above the dams were landlocked by the dams. It was also suggested that some individuals below the dams do not undertake amphidromous migration.
