A cutbow (Oncorhynchus clarkii × mykiss) is an interspecific fertile hybrid between a rainbow trout (Oncorhynchus mykiss) and a cutthroat trout (O. clarkii). Cutbow hybrids may occur naturally where the native ranges of both species overlap, such as between coastal rainbow trout (O. mykiss irideus) and coastal cutthroat trout (O. clarkii clarkii) and between Columbia River redband trout (O. mykiss gardineri) and westslope cutthroat trout (O. clarkii lewisi). While natural separation of spawning habitat limited hybridization in most native populations of rainbows and cutthroats, introduction of non-native hatchery-raised rainbow trout into the native ranges of cutthroat subspecies increased the rate of hybridization. Some native cutthroat populations are, as a result, at risk due to genetic