There are roughly ten subspecies of cutthroat trout described by Behnke (1992). They have the same morphology, but their coloration and spotting vary. Coastal cutthroat trout, O. c. clarki, are silvery to brassy in coloration with yellowish and irregular shaped spots. West slope cutthroat trout, O. c. lewisi, are silver in coloration with a yellowish tint, but can sometimes be bright yellow, orange, or red. Their spots are similar to those of coastal cutthroat except they do not extend below the lateral line. Yellowstone cutthroat trout, O. c. bouvieri, are yellowish brown, silver, or brass in coloration with round spots evenly distributed over the body. Lahontan cutthroat trout, O. c. henshawi, are dull in coloration with large round spots evenly distributed over the entire body. Paiute cutthroat trout, O. c. seleniris, closely resemble the Lahontan cutthroat with a dull coloration, but unlike the Lahontan, Paiute cutthroat lack spots. Bonneville cutthroat trout, O. c. utah, have the same coloration and spotting as Yellowstone cutthroat with one exception, the spots are larger on Bonneville cutthroat. Colorado river cutthroat trout, O. c. pleuriticus, are strong red in coloration along the lateral line and their lower sides are colored yellow. They have spots but they vary by individual. Greenback cutthroat trout, O. c. stomias, are similar to Colorado River cutthroat in coloration, however greenback cutthroat trout have larger spots. Rio Grande cutthroat trout, O. c. virginalis, are similar to greenback cutthroat in both coloration and spotting. Rio Grande cutthroat have, in addition, close spotting on the caudal peduncle. Yellowfin cutthroat trout, O. c. macdonaldi, have the coloration of the greenback but have a silvery tint and their spots are irregular.
The subspecies all share the following characteristics: red slash marks just below their gill covers on the lower jaws (Trotter, 1987) and a scale count above the lateral line of more than 150 (Willers, 1991). Where cutthroat and rainbow trout ranges overlap, the two species can be distinguished by the presence of basibranchial teeth, or teeth on the base of the tongue (Trotter, 1987). Cutthroat trout posses them, while rainbow trout do not.
The average length for a cutthroat trout is between 20 and 40 cm while the average weight is between 2 and 4 kg. Surprisingly, the environment a cutthroat trout occupies may be the limiting factor on how big a cutthroat can get, with genetic control only being a factor in an optimal environment (Behnke, 1993).
Range mass: 19 (high) kg.
Average mass: 2-4 kg.
Range length: 99 (high) cm.
Average length: 20-40 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; polymorphic
Sexual Dimorphism: sexes alike