Illustration by Steven Schalla, FlyFishingtheSierra.com, used with permission
As with all cutthroats, check first for the distinct orange-red cutthroat slash below the jaw. The Colorado River Cutt is one of the most colorful, and will often exhibit a bright golden yellow body with a brassy green back and an orange tint along the belly. Spots are large, and uniformly distributed on the body and caudal fin, both above and below the lateral line.
Distinguishing the Colorado from its two closest relatives - the Rio Grande and Greenback - is difficult as there is substantial overlap in appearance. Rio Grande cutthroat trout possess similar coloration, but usually have fewer scales in and above the lateral line and more irregularly shaped spots on the caudal peduncle. Greenbacks trout tend to have larger spots and more scales in and above the lateral line.
Distinguishing Colorado from its more northern and western cousins is somewhat easier: a Yellowstone will have a drabber, yellowish brown, silvery, or brassy color body becoming paler by the belly, with medium sized spots; a Snake River Cutt will have drabber body color and many more, smaller spots; a Westslope Cutt will generally exhibit bright but different colors, with a yellow, orange, and red body, and more, smaller spots that won’t appear below the lateral line except near the tail; the Bonneville will have drabber coloration.