A few years ago, when I was still working as a newspaper reporter, I did a series of stories focusing on cutthroat trout in the West. Following the breadcrumbs left behind by the well-known fisheries biologist Dr. Robert Behnke, I traversed the Rockies, going from Montana to southern Colorado and from Utah to the slopes of the Eastern Sierra, all in an effort to assess the health—and the future—of the native trout of the western United States.
It was an exhaustive project and took a year to complete. I put my small SUV through its paces, driving some of the country’s loneliest roads only to meet with biologists, tribal fisheries managers and fishing guides who were busy working to protect or recover native cutthroat trout populations.
My favorite stop was outside Leadville, Colo., where the Colorado Division of Wildlife (now Colorado Parks & Wildlife) was working with the U.S. Fish and Wildlife Service to propagate and reintroduce the greenback trout, a subspecies of wild trout that were once thought to be extinct. The recovery team had stocked these revived trout into a handful of streams in the Arkansas and South Platte River drainages—the fish were “rediscovered” outside their native range in a small stream on the slopes of Pike’s Peak where they had been transplanted to provide a fishing for tourists visiting the area.
The effort met with modest success over time, but, unfortunately, it was later determined that the fish the team was working to “reintroduce” were not simple greenbacks. At some point, they would be “contaminated” with the genes of Colorado River cutthroat trout. It was a big hit at the time, but the effort to reintroduce the greenback continues and success is happening in matches and launches.
Colorado’s native trout got another boost in 2018, when CPW biologists identified eight distinct San Juan trout populations. Like the greenback, the San Juan was thought to be extinct. A distinct relative of the Colorado River cutthroat trout, the San Juan is native to the high-elevation streams of the San Juan River, which begins on the wooded slopes of Wolf Creek Pass above Pagosa Springs, Colo., and eventually to New Mexico and then to Utah where it meets the Colorado at Lake Powell.
The San Juan was rediscovered in the wild thanks to genetic testing done on century-old specimens preserved at the Smithsonian Museum of Natural History in Washington, DC, when the genetics of the preserved trout were compared to those of samples in the San’s distant headwaters. Juan, they were found to be identical – the San Juan cutthroat trout had returned from the dead. Today, CPW is working to preserve these isolated pockets of native San Juans, including an effort to remove non-native trout from Wolf Creek and reintroduce natives to that important tributary of the San Juan River.
But Colorado’s native trout history isn’t done being rewritten. An effort is underway this summer to find the trout thought to be extinct in the central part of the state. Once native to Twin Lakes southwest of Leadville and just over Independence Pass from Aspen, the yellowtail was rumored to grow large and stout in the high elevation lakes that are now an important reservoir in the upper Arkansas River drainage. But their last reported sighting was 120 years ago. Biologists with CPW are spending this summer and likely the next several summers sampling as many streams, ponds and wetlands in the Twin Lakes drainage in search of the only cutthroat trout believed to be native to the Arkansas River basin. The hope is to find remnant populations of walleye and, over time, work to reintroduce the native fish to other watersheds within its native range.
The inspiration? Success in identifying other native trout once thought to be extinct. The search for yellows really began when greenbacks suddenly appeared years ago, and then got a boost when San Juans were identified in the southern reaches of the state.
“We’re going into this research with our eyes open,” said Paul Foutz, senior fisheries biologist for CPW’s Southeast region. “We know the history of walleyes and that they haven’t been seen since before 1902. But millions of trout, native and non-native, have been back and forth across Colorado since before statehood. And if the story of the greenback and the San Juan River debacle teaches us anything, it’s that we should never stop looking.”
Like the San Juans, there are preserved specimens of cutthroat trout at the Smithsonian. This is a useful genetic resource—if the group of biologists looking for yellows can match genetics from any wild mushrooms found in the backcountry, yellows such as San Juan and coin green could be revived.
And, truth be told, biologists aren’t just tasked with roaming the Sawatch Range in search of streams and backcountry springs that may support hidden populations of native trout. Millions of trout were once bred by the Leadville National Fish Hatchery, and specimens were shipped far and wide across Colorado. Just as the green buck was discovered outside of its native range, it’s possible that yellows can appear almost anywhere they might have been planted more than 100 years ago. This effort isn’t just about wandering the woods in hopes of finding that needle in the haystack—biologists will examine historical stock records from nurseries and do some ground truthing in other drainages where yellowfins may to exist now without anyone knowing. working on efforts through CPW.
Part of what makes the search for yellowtails so interesting is the fish’s life history—it was a piscivore that roamed the Twin Lakes and grew quite large. According to Behnke’s research (the renowned biologist died in 2013), the first reported encounter with yellows was in 1885 by Colorado fish commissioner John Pierce, who described the fish as having yellow markings and, surprisingly, flesh yellow. And, the report says, the fish weighed 10 kilograms.
Three large yellowfin trout were sent to US President William Henry Harrison in 1891 (photo: Sports Afield).
Behnke also noted that there was an attempt to introduce yellowfin into Island Lake on Grand Mesa, far to the west, but reports of the fish persisting there into the 1930s are unsubstantiated. And, in an interesting little study: David Starr Jordan, who documented yellowfins for the US Fish Commission in 1889, reported in his autobiography, Days of Man, published in 1922, that yellowfins ” were successfully introduced into France from eggs sent by … the Leadville hatchery.”
But the search is likely to start closer to home. In a 2020 study, there are 236 waters that have no stock data, meaning it is possible that no fish, native or otherwise, have been stocked in them. These lakes and streams are probably the best places to start looking for walleyes.
“Although these fish are no longer present in the Twin Lakes, there is a possibility that a remnant population with pure genetics may be found in the high mountain lakes, tributaries and drainages of the Twin Lakes,” said Alex Townsend, an aquatic biologist with CPW .
A drawing by a David Starr Jordan and Barton W. Evermann, 1907 (Illustration courtesy: Freshwater and Marine Image Bank at the University of Washington).
The walleye die-off in Twin Lakes is likely attributable to two factors. First, mining in the area was very prominent in the area in the late 1800s, which not only contaminated rivers and streams with mine acid runoff, but also resulted in many trout being caught for food for the growing mining camps. . Second, non-native trout are likely to push the yellow over the edge—when the lakes were sampled in the early 1900s, rainbow trout were the featured fish.
Despite the fact that it’s been more than a century since they were last documented, the team of biologists searching for a remnant population of one of Colorado’s four native cutthroat trout subspecies remains hopeful.
“I know how exciting it was to find out that green trout still existed in our waters,” Foutz said. “Our world shrinks every time a species goes extinct. The quest for yellow is in fulfillment of CPW’s core mission to perpetuate the state’s wildlife resources. Based on our recent discoveries of hidden green coins and San Juan scratches, we’d be remiss if we didn’t look for yellow.