One disappeared, two were rediscovered, and all three changed what we know about Colorado’s native trout. For more than a century, people moved trout across the West from one watershed to another with little hesitation or care about where they belonged. Hatcheries stocked fish wherever they pleased, causing non-native trout to compete with native populations—the unfortunate truth behind many Western fisheries.
The damage to native species was done, and only now are we discovering just what was lost. Recent advances in DNA technology gave biologists the tools to untangle the genetic mess early settlers left behind. Paired with century-old museum specimens and a vast DNA database, biologists are now discovering new species once misidentified or thought extinct. These are the stories of Colorado’s lost cutthroat trout.
The Yellowfin Cutthroat
Colorado’s biggest cutthroat trout is one of its most mysterious. The yellowfin cutthroat was native to the Twin Lakes near Leadville, CO. While not much is known about them today, reports from the time claim these fish had yellow fins, yellowish skin, and could weigh as much as 10+ pounds.
Scientists in 1889 were the only group to formally document these fish, having collected many specimens that were later preserved in museums. Those old jars hold some of the limited physical evidence that the yellowfin actually ever existed. Just a short time later, surveys in 1902 and 1903 found no yellowfin. Many factors, such as the introduction of rainbows, competition, hybridization, and commercial harvesting, most likely played major roles in the fish’s extinction.
Colorado’s other “extinct” cutthroat have shown us that there is a chance that a small population may still be out there. Recently, Colorado Parks and Wildlife biologists have begun searching for the lost species in the upper Arkansas River Basin, in small creeks, lakes, and ponds, in hopes they survived in an overlooked area. The search has yet to be successful, and the fish is still considered extinct.
The Greenback Cutthroat
The greenback cutthroat was declared extinct back in 1937. Then, in the 1950s, people speculated that several populations possibly descended from greenbacks were being discovered in the Colorado mountains.
Those fish marked the foundation of a major recovery effort for the greenbacks. They began to reproduce, were stocked into many new waters, and it paid off; soon after, the Endangered Species Act moved them from endangered to threatened. In 1994, the greenback cutthroat was named Colorado’s state fish. But there were slight issues…most of them weren’t actually greenbacks.
DNA testing eventually revealed that those years of stocking moved different cutthroat lineages far from their native watersheds. Turns out many of the fish protected as greenbacks were just relatives of the Colorado River cutthroat from the western slope.
Finding the real greenback was not easy; scientists had to compare living trout with museum specimens collected from known locations in the 1800s. There was only a very small surviving population that matched, and it was only a few hundred fish that were living in a short section of Bear Creek near Colorado Springs. But this didn’t make much sense because Bear Creek is outside Greenback’s native South Platte River drainage, and it was most likely fishless before humans arrived.
The most reasonable explanation points to Joseph C. Jones; he was a prospector who homesteaded along a popular route to Pikes Peak in the 1870s. Jones dreamed of building a hotel and restaurant for travelers heading toward the summit. To help attract visitors, Jones built several fish ponds on his property that historians believe he stocked with greenback cutthroat brought over from the South Platte drainage. The hotel was never finished, but the fish remained. Eventually, some of those fish most likely escaped into Bear Creek.
Natural barriers in Bear Creek kept other trout from moving upstream and reproducing with the greenbacks. This allowed the small population to remain genetically pure while the fish disappeared from nearly everywhere they naturally belonged. The last true greenbacks had survived in a creek they were never supposed to be in, all because someone had moved them there more than a century earlier.
Stocking fish across Colorado was one of the main reasons native cutthroat populations became so difficult to identify. But in this one case, stocking a fish in the wrong place may have saved it from extinction. Today, descendants of the Bear Creek greenbacks are being raised in hatcheries and returned to protected waters within their native South Platte drainage.
The San Juan Cutthroat
The story of the San Juan cutthroat begins with just two fish that sat in the Smithsonian for more than 100 years. A famous naturalist, Charles Aiken, collected the specimens near Pagosa Springs in 1874 and sent them to the museum to be studied and preserved. When researchers began using DNA to better understand Colorado’s native cutthroat, those two fish became incredibly important.
After testing the specimens, it was discovered they belonged to a distinct lineage of cutthroat native to the San Juan River Basin. At the time, it was thought that no living populations matched them, and so they declared the San Juan cutthroat extinct.
Crews searched remote streams across southwest Colorado, collecting small fin clips from cutthroat along the way. Those samples were then compared with the DNA from the fish collected in 1874. Colorado Parks and Wildlife announced in 2018 that eight small populations had been found with genetics that very closely matched the old museum specimens. The San Juan cutthroat had been rediscovered, nearly 150 years later.
That same year, the 416 Fire burned through the San Juan National Forest and threatened one of the recently discovered populations. Ash, sediment, and debris from this massive fire made it very possible that the small population could be gone. A group of biologists sprang into action, heading to two remote creeks to capture 58 cutthroat before post-fire runoff could reach them. They safely transported the fish to the Durango Fish Hatchery, where they were protected and, in time, used to help rebuild the population throughout the San Juan Basin.
What Else Is Out There?
The stories of Colorado’s lost cutthroat show just how complicated the state’s trout history really is. People moved millions of fish across watersheds before anyone fully understood their genetic differences. Those decisions created many fishing opportunities, but also put many native species at risk.
Without the specimens sitting in museums, we may have never known that the greenbacks being protected were the wrong fish. We may have never known that the San Juan cutthroat was different from the other cutthroat in the region. And we would have even less evidence that the massive yellowfin ever existed. Could there be other cutties out there? If these fish have taught us anything, it is that lost does not always mean gone.