The specimen used in this study was 42 f ish of seven groups of ayu, Plecoglossus altivelis, and they should be one clone induced art ificially or samples obtained from the eggs of amphidromous form inseminated by the sperm of the individuals of the same clone. The genomic DNA were extracted from caudal fin of adult or all f ish of larva and microsatellite DNA were amplified by PCR. The genotypes of individuals were identif ied according to electrophoretic patterns of the products of PCR. The results suggest 22 fish of ò, ó, . and × groups be one clone, because they have the same genotypes at two loci of Pal- 1* and Pal- 2* respectively. 10 f ish of × group were gynogenet ic diploids induced successfully and one clone. 1 f ish of . is other type fish. 19 f ish of . and . groups were offspring of ., ò or ó and amphidromous form.