The Beardslee trout (Oncorhynchus mykiss irideus f. beardsleei), formerly Salmo gairdneri beardsleei) is a local form of rainbow trout endemic to Lake Crescent in Washington. By some sources, they are treated as a subspecies. Known to locals as "bluebacks", Beardslee trout are found nowhere else, and spawn in the Lyre River, near the outlet of the lake. Beardslee are somewhat difficult to distinguish from the Lake Crescent cutthroat trout, which is also endemic to Lake Crescent, as they only take on the Rainbow colors during spawning.