The most diverse trout species in North America, the historical distribution of cutthroat trout covers the broadest range of any stream dwelling trout in the Western Hemisphere. The rugged topography of their range has lead to isolation, which in turn has given rise to fourteen recognized subspecies. Four of these evolved in Colorado: the Colorado River cutthroat trout in drainages west of the continental divide, Greenback cutthroat trout in the South Platte and Arkansas River drainages, and the Rio Grande cutthroat trout in streams that drain into the San Luis Valley. In addition, the yellowfin cutthroat trout was historically found in Twin Lakes at the headwaters of the Arkansas drainage.
Unfortunately, this predator that grew to over 10 lbs, is now extinct. All three remaining species have either been petitioned to be listed or are currently listed under the Endangered Species Act. Dramatic reductions in their range have been precipitated primarily by the introduction of nonnative salmonids. Specifically rainbow trout that hybridize with cutthroat trout, and brook and brown trout that tend to replace them in streams and rivers. In an effort to preserve the legacy of these fish, multi-agency conservation teams have been established for each subspecies.