Can fish come back from the dead?
Over the past decade, aquatic biologists and Colorado Parks and Wildlife researchers have confirmed the existence of native greenback cutthroat trout long after they were thought to be extinct.
CPW biologists also discovered the San Juan River’s only cutthroat trout after it was also thought to be extinct.
So why couldn’t the legendary Cutthroat Yellowfin, a giant among cutthroats last seen in Colorado waters at Twin Lakes near Leadville in the early 20th century, still lurk somewhere in the Colorado landscape?
The idea that yellowfin tuna still exist and could be found clearly is a long shot. But CPW Aquatic Biologist Alex Townsend and CPW Southeast Region Senior Aquatic Biologist Paul Foutz are on a quest for discovery.
Given hope by the other recent cutthroat revelations, Foutz, Salida-based aquatic biologist Townsend and even retired CPW aquatic biologist Greg Policky – a cutthroat trout expert with over 30 years of experience experience – will spend the next few summers surveying hundreds of wetlands, streams and ponds in the upper Arkansas River basin in search of yellowfin tuna, thought to be the only cutthroat native to the Arkansas River watershed.
CPW aquatic biologists regularly survey the state’s water to study the health of various fish populations. The quest for yellowfin only broadens the field of annual surveys.
Foutz and Townsend are betting they could uncover a hidden yellowfin population after witnessing what happened in 2012 when Colorado’s fishing community was rocked when aquatic biologists at CPW announced that genetic testing DNA researchers 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 watershed to the north — were, indeed, the long-lost Greenback, the fish of the State of Colorado.
“We’re going into this research with our eyes wide open,” Foutz said. “We know the history of yellowfin tuna and that it hasn’t been seen since before 1902. But millions of trout, native and non-native, have been going back and forth through Colorado since before the inception of the state. And if the story of the greenback and the cutthroat of the San Juan River teaches us anything, it’s that you should never stop looking.
The story of the Colorado cutthroat trout is a story of fish that have evolved over ages in the western United States. Eventually, 14 distinct subspecies were recognized, four of which originated in Colorado: the giant cutthroat yellowfin tuna, a strain from the Arkansas Basin; the cutthroat of the greenback east of the watershed; the cutthroat of the Colorado River from the western slope; and the cutthroat Rio Grande in the streams surrounding the San Luis Valley.
Yellowfin tuna and the greenback feared being lost a century ago mainly due to water pollution from mining, habitat degradation, overfishing and competition from aggressive, non-native brook, brown and rainbow trout.
The disappearance of yellowfin tuna after the arrival of white settlers was incredibly rapid given the history of the cutthroat trout, which is considered by scientists to be one of the most diverse fish species in North America.
Yellowfin tuna were first documented in July 1889 by David Starr Jordan and GR Fisher who visited Twin Lakes and published their findings in the 1891 Bulletin of the U.S. Fish Commission. Jordan was a world-renowned scientist and ichthyologist who served as founding president of Stanford University after it opened in 1891.
They collected seven specimens of yellowfin tuna and eight specimens of greenback trout. These seven specimens are the only evidence of the existence of the cutthroat yellowfin tuna with five preserved at the Smithsonian Museum of Natural History in Washington, D.C.
Jordan reported yellowfin reaching weights of 10-12 pounds and feeding on smaller fish. These fish were lake specialists and grew very large.
Modern Colorado scientist Robert Behnke, fisheries biologist and world authority on trout, wrote about yellowfin and Jordan specimens in his own “Monograph of the Native Trout of the Genus Salmo of Western North America. North” of 1979.
Behnke examined them and described “small star-shaped specks and silver coloration” of yellowfin tuna. He declared them “clearly recognizable and easily differentiated from the dark coloration and pronounced large round spots of greenback trout specimens”.
Yellowfin tuna were only known to live in the Twin Lakes and were propagated at the Leadville National Fish Hatchery from 1892 to 1905 and introduced to many Colorado lakes.
Indeed, millions of fish were spawned at the Leadville Hatchery and spread all over Colorado. About 10 years ago, US Fish and Wildlife Service fisheries biologist Chris Kennedy gathered stocking records and documented that between 1889 and 1925, more than 50 million cutthroat trout from the Gunnison and White River were seeded throughout Colorado, including locations on the Front Range. .
Additionally, from 1914 to 1925, the state fisheries commission produced at least 26 million trout and stocked them in virtually every county in the state that could support trout.
In many cases, non-native fish have supplanted less aggressive native fish. They also interbred with the native fish, diluting their lineages. Eventually, non-native fish invaded many waters.
Surveys of Twin Lakes in 1902 and 1903 failed to find any yellowfin tuna.
Behnke said the first mention of “a large silver trout in the Twin Lakes” was made in the 1885-1886 report of Colorado Commissioner of Fisheries John Pierce. In his report, Pierce writes that a 10-pound trout with yellow colors and yellowish flesh was found at Twin Lakes. He also wrote that an attempt had been made to transplant trout into Island Lake at Grand Mesa.
Behnke suggested that yellowfin fell victim to non-native trout introduced in large numbers to the Twin Lakes in the 1890s. Surveys from 1902-1903 from Twin Lakes showed that non-native rainbow trout were dominant . He also found hybrids of greenbacks and rainbows. Greenbacks also quickly disappeared from Twin Lakes.
Yellowfin tuna were reported in Island Lake as late as the 1930s. But these reports were unsubstantiated.
Another tantalizing clue to 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 to France from ‘eggs shipped from . . . Leadville Hatchery.
Behnke, in 1979, was not very optimistic about the chances of finding Yellowfin in Colorado.
“There is a remote possibility that yellowfin trout were once stocked in an arid lake where they may have spawned and that no other trout were later stocked in this lake. Even if such a situation existed , there is no way to verify that a trout is the original Twin Lakes Yellowfin Trout.
“More is unlikely to be known about yellowfin trout. The mystery of its origin and its validity. . . whether native or introduced, will never be resolved.
Maybe not. But Foutz, Townsend and Policky don’t give up so easily. Especially given modern methods of genetic testing that make species identification much easier.
The Upper Arkansas River Basin contains many small lakes, streams, ravines, and watersheds that have been rarely or never sampled.
In 2020, an Upper Arkansas Basin survey identified 236 waters with no stocking and no survey records. And it is only in recent decades that fish stocking in the Upper Arkansas River basin has been well documented. There are few accurate records of waters stored during Colorado’s territorial days and statehood.
“Historic mining activity in the area often resulted in the displacement of fish to provide a food source and this was often poorly documented, if at all,” Townsend said. “These waters may contain valuable cutthroat trout populations of unknown genetic origin.
“Although these fish no longer occur in Twin Lakes, it is possible that a remnant population with pure genetics may be found in high mountain lakes, tributaries and watersheds of Twin Lakes.”
Townsend and Policky, along with a team of aquatic biology technicians, will begin sampling in June, starting with the Twin Lakes area. For the 2023, 2024 and 2025 sampling years, a separate team of technicians will be dedicated to this project and will work independently to collect the data.
This project will continue until all identified potential waters have been investigated and documented and the genetics of all fin clips have been analyzed. Sampling for this project will take place during the summer months when these areas are free of snow and obstructions, and seasonal technicians will be most available.
Crews will electrofish, net, and even use hook and line methods as they work through a list of predetermined lakes, streams, ravines, 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.
“It’s a very exciting opportunity to explore these uncharted waters in search of yellowfin tuna,” Policky said. “I have dedicated my career to learning all about these fish and I am honored to be part of the CPW team conducting this research.”
Foutz said the team will report back on its findings as the project progresses and is eventually completed.
“I know how exciting it was to find out that greenback cutthroat trout still existed in our waters,” Foutz said. “Our world is diminished every time a species goes extinct. The search for yellowfin tuna is fulfilling CPW’s core mission to perpetuate the state’s wildlife resources. Based on our recent discoveries of hidden cutthroats from Greenback and San Luis, we’d be remiss if we didn’t look for yellowfin tuna.