When European and eastern American explorers and settlers moved west, they brought with them brook and brown trout. Later, when people migrated from the Pacific coast to the Rockies, they brought with them rainbow trout. One hundred years ago, brook trout, rainbow trout, and brown trout had already replaced cutthroats through most of their native range. In most cases, native populations were degraded through overfishing, loss of habitat, and competitive losses through the introduction of exotic species. Rainbow trout introductions proved especially troublesome, as rainbows and cutthroats can interbreed, quickly diluting the unique genetic attributes of native species.

The pure strains of "native" cutthroats that exist today are in a few isolated pockets, usually in remote locations upstream of impassable natural barriers. They're the exception, not the rule.

Exotic species were also introduced to the Park but perhaps because the habitat remained intact, or perhaps because they were never harvested to extinction, Yellowstone Cutthroat trout have fared better than some other types of cutthroats in the American West. Yellowstone National Park is considered by some as the birthplace of "catch-and-release" fishing, and today, the fishing for native trout is better than most people can remember.

Like all cuttroat trout, yellowstone cutts have a red or orange slash mark on the under side of their lower jaw. They are generally a brassy yellow in color, with a pronounced, rounded black spots on the back and sides. In river-dwelling trout, these spots will be more concentrated near the back half of the fish. In Yellowstone Lake, the cutts have more evenly distributed spots. Some adults have a red or pinkish tint on their gill plates and/or down their flanks, reminiscent of a rainbow trout.