Detection and morphological characteristics of “Kunimasu” (Oncorhynchus kawamurae)/”Himemasu” (O. nerka) hybrids in Lake Motosu, Yamanashi Prefecture, Japan

Abstract

A recently discovered transplanted population of “Kunimasu” (Oncorhynchus kawamurae) in Lake Saiko, Yamanashi Prefecture, Japan, extinct in its original habitat, has been reported as almost never hybridizing with sympatric “Himemasu” (O. nerka). However, analyses of microsatellite and mitochondrial DNA markers disclosed extensive hybridization between these two species in Lake Motosu, Yamanashi Prefecture, a second lake to which Kunimasu had been transplanted. The rates of purebred Kunimasu, Kunimasu/Himemasu hybrids and purebred Himemasu were 0 %, 64.3 % and 35.7 %, respectively, and hybrid specimens had intermediate numbers of pyloric caeca and gill rakers compared with the parental species.