Article ID: 24-00028
We investigated the strain identification between hatchery-reared and landlocked ayu Plecoglossus altivelis altivelis using meristic character (number of scales above the lateral line based on the dorsal fin ray) and otolith Sr:Ca ratios in the upper reaches of Kagami Dam Lake in the Kagami River. The percentages of landlocked and hatchery ayu in angling (tomozuri) caught fish in May–September in 2017 were 17–92％ and 8–83％, respectively. Using microsatellite DNA markers, we examined the reproduction of landlocked and hatchery ayu in Kagami Dam Lake. The genetic origin of parent and upstream migrated populations in the landlocked form in Kagami Dam Lake was identified as hybrid fish between amphidromous and Lake Biwa strains using assignment tests. Moreover, among the spawning in November and December, 23–27％ of individuals were identified as amphidromous strain, suggesting that hatchery-reared ayu contributed to the reproduction. These results indicated the contribution of hatchery-reared ayu to the reproduction and enhancement of resources in Kagami Dam Lake and its upper reaches. However, most individuals within the upstream migrated population were identified as hybrid fish. This indicates that most of the ayu in Kagami Dam Lake are hybrid fish, and their reproduction contributes to the persistence of the population.
