1Graduate school of Biosphere Science, Hiroshima University, Higashi-hiroshima, Hiroshima 739-8528, 2The Research Institute of Marine Bioresources, Fukuyama University, Onomichi, Hiroshima 722-2101, 3Nihon Total Science Inc., Fukuyama, Hiroshima 720-0832, Japan
Strain identification to assess the stock efficiency of ayu Plecoglossus altivelis altivelis was performed using microsatellite DNA loci, otolith Sr/Ca ratio and scale number above the lateral line at the Nariwa River, a tributary of the Takahashi River, in western Japan. The specimens collected by angling from mid-July to August represented 61.7% for the transplanted landlocked form (from Lake Biwa), 28.3% for native landlocked form (from Lake Nariwa), 1.7% for the transplanted amphidromous form, and 8.3% for hatchery-reared, while the specimens collected by gill net in September were identified as 58.6% for the transplanted landlocked form, 3.5% for the native landlocked form, and 37.9% for the hatchery-reared without transplanted amphidromous form. We discussed the effectiveness of stock separation markers for practical usage and the stock contribution status in each strain through the stocking program.