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Zombie Fish? CPW aquatic biologists embark on search for long-lost Yellowfin cutthroat trout

Bill Vogrin
Southeast Region Public Information Officer

Zombie Fish? CPW aquatic biologists embark on search for long-lost Yellowfin cutthroat trout

This copyright illustration of the extinct Yellowfin cutthroat trout was created by Joseph Tomelleri. Used with permission. Mandatory credit required.

July 1, 2022

Zombie Fish? CPW aquatic biologists embark on search for long-lost Yellowfin cutthroat trout

SALIDA, Colo. – Can fish come back from the dead?

In the past decade, Colorado Parks and Wildlife aquatic biologists and researchers have confirmed the existence of native Greenback cutthroat trout long after they were believed to be extinct. 

CPW biologists also discovered the unique San Juan River cutthroat trout after they, too, were thought to be extinct.

So why couldn’t the legendary Yellowfin cutthroat, a giant among cutthroat last seen in Colorado waters in Twin Lakes near Leadville at the turn of the 20th century, still be hiding somewhere on the Colorado landscape?

The idea that the Yellowfin still exists and might be found clearly is a longshot. But Alex Townsend, CPW aquatic biologist, and Paul Foutz, CPW’s Southeast Region senior aquatic biologist, are on a quest to find out. 

Given hope by the other recent cutthroat revelations, Foutz, the Salida-based Townsend and even retired CPW aquatic biologist Greg Policky – an expert on cutthroat trout with more than 30 years’ experience – will spend the next few summers surveying hundreds of wetlands, streams and ponds in the upper Arkansas River basin searching for the Yellowfin, believed to be the only cutthroat native to the Arkansas River drainage.

CPW aquatic biologists routinely survey the state’s water to study the health of various fish populations. The quest for the Yellowfin simply broadens the scope of the annual surveys.

Foutz and Townsend are gambling they might uncover a hidden Yellowfin population after witnessing what happened in 2012 when Colorado’s fishing community was rocked when CPW aquatic biologists announced genetic DNA testing had confirmed a small population of spotted trout found in tiny Bear Creek in Colorado Springs – far from their native waters in the South Platte River drainage to the north – were, indeed, the long-lost Greenback, Colorado’s state fish.

“We are going into this search with our eyes wide open,” Foutz said. “We know the history of the Yellowfin and that it hasn’t been seen since before 1902. But millions of trout, native and nonnative, have been back and forth across Colorado since before statehood. And if the history of the Greenback and San Juan River cutthroat teach us anything, it’s that we should never stop looking.”

The history of Colorado cutthroat trout is a story of fish that evolved over the eons across the western U.S. Eventually, a distinct 14 subspecies came to be recognized including four native to Colorado: the giant Yellowfin cutthroat, an Arkansas Basin strain; the Greenback cutthroat east of the Continental Divide; the Colorado River cutthroat from the western slope; and the Rio Grande cutthroat in streams surrounding the San Luis Valley.

Both the Yellowfin and Greenback were feared lost a century ago due primarily to water pollution from mining, habitat degradation, overfishing and competition from aggressive and non-native brook, brown and rainbow trout.

The demise of the Yellowfin after the arrival of white settlers was shockingly swift given the history of cutthroat trout, which are considered by scientists to be one of the most diverse fish species in North America. 

The Yellowfin was first documented in July 1889 by David Starr Jordan and G. R. Fisher who visited Twin Lakes and published their discoveries in the 1891 Bulletin of the U.S. Fish Commission. Jordan was a world-renowned scientist and ichthyologist who was founding president of Stanford University after it opened in 1891.

They collected seven Yellowfin and eight greenback trout specimens. Those seven specimens are the only evidence of Yellowfin cutthroat in existence with five housed at the Smithsonian Museum of Natural History in Washington, D.C. 

Jordan reported that Yellowfins reached weights of 10-12 pounds and fed on smaller fish. These fish were lake specialists and grew very large. 

Modern-day Colorado scientist Robert Behnke, a fisheries biologist and world authority on trout, wrote of the Yellowfin and Jordan’s specimens in his own 1979 “Monograph of the native trouts of the genus Salmo of western North America.”

Behnke examined them and described “small, star-shaped spots and silvery coloration” of the Yellowfin. He pronounced them “clearly recognizable and readily differentiated from the dark coloration and pronounced, large, round spots of the Greenback trout specimens.”

Yellowfin were only known to live in Twin Lakes and were propagated at the Leadville National Fish Hatchery from 1892 to 1905 and introduced to many lakes across Colorado. 

Indeed, millions of fish were spawned at the Leadville hatchery and spread far and wide across Colorado. About 10 years ago, U. S. Fish and Wildlife Service’s fisheries biologist Chris Kennedy pieced together stocking records and documented that between 1889 and 1925, more than 50 million cutthroat trout from the Gunnison and White River Basins were stocked across Colorado, including locations on the Front Range.

Further, from 1914-25, the state fish commission produced at least 26 million trout and stocked them in virtually every county in the state that could support trout.

In many cases, nonnative fish outcompeted less aggressive, native fish. They also cross-bred with the native fish, diluting their bloodlines. Eventually the nonnative fish took over many waters.

Surveys of Twin Lakes in 1902 and 1903 failed to find any Yellowfin. 

Behnke said the first mention of “a large, silvery trout in Twin Lakes” was made in the 1885-86 Report of the Colorado Fish Commissioner, John Pierce. In his report, Pierce wrote that a 10 pound trout of yellow colors and with yellowish flesh was found in Twin Lakes. He also wrote that an attempt was made to transplant the trout into Island Lake on Grand Mesa.

Behnke suggested Yellowfin fell victim to nonnative trout introduced in Twin Lakes in large numbers in the 1890s. The 1902-03 surveys of Twin Lakes showed nonnative rainbow trout were dominant. He also found hybrids of greenbacks and rainbows. Greenbacks soon disappeared from Twin Lakes, too.

There were reports of Yellowfin in Island Lake into the 1930s. But those reports were unsubstantiated.

Another tantalizing clue for Foutz and his team is a note in Jordan’s autobiography, “Days of a Man,” published in 1922. Jordan said Yellowfin trout were “successfully introduced into France from eggs shipped from the . . . Leadville hatchery.” 

Behnke, in 1979, was not terribly optimistic about the chances of finding Yellowfin in Colorado.

“There is a remote possibility that the Yellowfin trout was once stocked into a barren lake where it was able to reproduce and no other trout was later stocked into that lake. Even if such a situation existed, there is no way a trout could be verified as the original Yellowfin trout of Twin Lakes.

“It is not likely that any more will ever be known concerning the Yellowfin trout. The mystery of its origin and validity . . . whether native or introduced, will never be solved.”

Maybe not. But Foutz, Townsend and Policky aren’t giving up so easily. Especially given modern genetic testing methods that make it much easier to identify species.

The Upper Arkansas River basin contains many small lakes, streams, gulches and drainages that have been seldom sampled or never sampled. 

In 2020, a survey of the Upper Arkansas basin identified 236 waters that had no stocking and no survey records. And only in recent decades have fish stocking in the Upper Arkansas River basin been well-documented. There are few precise records of waters stocked during Colorado’s territorial days and statehood.

“Historical mining activity in the area often resulted in the movement of fish to provide a food source and this was often poorly documented if at all,” Townsend said. “These waters may contain valuable populations of cutthroat trout of unknown genetic origin.

“Although these fish are no longer present in Twin Lakes, the possibility exists that a remnant population with pure genetics might be found in the high mountain lakes, tributaries and drainages to Twin Lakes.” 

Townsend and Policky, with a team of aquatic biology technicians, began sampling in June, starting in the Twin Lakes region. For sampling years 2023, 2024 and 2025 a separate crew of technicians will be dedicated to this project and will work autonomously to collect data. 

This project will continue until all potential waters identified have been surveyed and documented and the genetics from all fin clips have been analyzed. The sampling for this project will occur during the summer months when these areas will be free of snow and impediments, and seasonal technicians will be most available. 

Crews will electro-fish, net and even use hook-and-line methods as they work down a list of predetermined lakes, streams, gulches and drainages within the Upper Arkansas River Basin. 

Tissue samples from the caudal fin of trout found in the target waters will be collected and analyzed for genetic composition.

“This is a very exciting opportunity to explore these uncharted waters in search of the Yellowfin,” Policky said. “I dedicated my career to learning everything possible about these fish and I’m honored to be part of the CPW team conducting this search.”

Foutz said the team will report its findings as the project progresses and eventually concludes.

“I know how exciting it was to discover that Greenback cutthroat trout still existed in our waters,” Foutz said. “Our world is diminished anytime a species goes extinct. Searching for the Yellowfin is the fulfillment of CPW’s basic mission of perpetuating the wildlife resources of the state. Based on our recent discoveries of hidden Greenback and San Luis cutthroats, we’d be remiss if we didn’t search for the Yellowfin.”




One of seven specimens of Yellowfin cutthroat trout collected by David S. Jordan and Barton W. Evermann from Twin Lakes near Leadville in 1889 and preserved at the Smithsonian Museum of Natural History in Washington D.C.

Map of the native ranges of cutthroat trout in Colorado. Yellowfin cutthroat were believed to be native to the Arkansas River basin; Rio Grande cutthroat are native to the Rio Grande River;  Greenback cutthroat are native to the South Platte River drainage; and Colorado River cutthroat are native to the Colorado River drainage.

Three large Yellowfin cutthroat trout were sent to U.S. President William Henry Harrison in 1891. Photo courtesy of Sports Afield.

A drawing of a Yellowfin David Starr Jordan and Barton W. Evermann, 1907. Illustration courtesy of the Freshwater and Marine Image Bank at the University of Washington.

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