Illustration by Steven Schalla, FlyFishingtheSierra.com, used with permission
Yellowstone Cutts come in two variants: Large and Fine Spotted. This describes the Large Spotted variant. The fine spotted variant is also known as the Snake River Cutthroat.
As with all cutthroats, check first for the distinct orange-red cutthroat slash below the jaw. The Yellowstone will have a drab, yellowish brown, silvery, or brassy color body becoming paler by the belly, with medium sized spots that are often concentrated by the caudal (tail) fin.
Compared to other cutthroat whose range overlaps or abuts the Yellowstone’s: a Snake River Cutt will have similar coloration and patterning but many more, smaller spots; a Westslope Cutt will have spots by the tail and none on its flanks near its pectoral fin; a Colorado River Cutt will generally exhibit much brighter colors, with a bright, golden yellow body, a brassy green back and an orange tint along the belly; the Bonneville will have similar coloration, but fewer, larger, and more uniformly distributed spots. Note that the location you catch the fish may be a more reliable indicator of species than direct observation: local variations mean that even experts have difficulty identifying sub-species definitively without genetic analysis.