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Trout species thought to be extinct found alive in Southwest Colorado

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Thursday, Sept. 6, 2018 12:05 AM
Wildlife experts have been able to match cutthroat trout samples collected in 1874 to eight small populations of trout found in the San Juan River basin.

A native species of trout thought to be extinct was found alive and well recently in Southwest Colorado.

Colorado Parks and Wildlife announced the discovery of a “unique genetic lineage” of the Colorado River cutthroat trout Tuesday, saying that genetic testing of the fish’s DNA was confirmed earlier this year.

The fish were found in eight small populations, CPW said, in streams of the San Juan River basin within the San Juan National Forest and on private property, surviving in isolated habitats and naturally reproducing.

To protect the fish, CPW is not releasing where in the San Juan River basin the cutthroat were found.

“Anyone who just looked at these fish would have a difficult time telling them apart from any other cutthroat; but this is a significant find,” said Jim White, an aquatic biologist for CPW in Durango, in a prepared statement.

“Now, we will work to determine if we can propagate these fish in our hatcheries and reintroduce them into the wild in their historic habitat. It’s a great conservation effort and a great conservation story,” he said.

Colorado Parks and Wildlife has found a cutthroat trout species thought to be extinct. The agency has plans to develop a strategy to reintroduce the fish in rivers throughout the region.
Courtesy of Colorado Parks and Wildlife

Cutthroat trout originated in the Pacific Ocean and have spread to cold streams and rivers throughout the American West, evolving through geographic isolation into 14 different subspecies.

Three subspecies are found in Colorado: the Colorado River cutthroat trout, found west of the Continental Divide; the greenback cutthroat trout in the South Platte River basin; and the Rio Grande cutthroat trout in the San Luis Valley.

A fourth species, the yellowfin cutthroat trout, native to the Arkansas River basin, went extinct in the early 1900s, according to CPW.

But for the three remaining cutthroat species, CPW over the years has done its part to see the fish’s survival through breeding in captivity and stocking in rivers across the state, along with other conservation management strategies.

In Southwest Colorado, for instance, CPW along with partner agencies are on track to restore 23 miles solely to the native cutthroat trout in Hermosa Creek, north of Durango, which will be the longest continuous stretch in the state.

For more than 30 years, biologists have been surveying remote creeks in Southwest Colorado, looking for isolated populations of cutthroat trout and finding some unknown species long before genetic testing became available.

“The biologists understood that isolated populations might carry unique genetic traits and adaptations, so they made sure to preserve collected samples for genetic testing later,” said Joe Lewandowski, spokesman for CPW, in a prepared statement.

“Significant advances in genetic testing technology over the last 10 years were instrumental in finding the distinct genetic markers that identify the San Juan lineage trout as being unique,” he said.

Wildlife experts were able to tie the cutthroat found in the San Juan River basin to fish samples collected and preserved in 1874 by naturalist Charles E. Aiken, who donated two trout to the Smithsonian National Museum of Natural History.

“Careful work over the years by biologists, finding those old specimens in the museum and the genetic testing gave us the chance, essentially, to go back in time,” White said. “Now, we have the opportunity to conserve this native trout in Southwest Colorado.”

Lewandowski said a conservation plan will be developed over the next few years for the cutthroat, but developing a brood stock to be reintroduced in waterways will be key in distributing them to suitable habitat.

“These fish were discovered because of our curiosity and our concern for native species,” said John Alves, CPW aquatic biologist based in Durango, in a prepared statement.

“We’re driven by scientific inquiry that’s based on hard work and diligence. This is a major discovery for Colorado, and it shows the critical importance of continuing our research and conservation work,” he said.

Native cutthroat have struggled to survive across the state, battling low stream flows, degrading water quality and competition with other introduced fish species, like rainbow, brown and brook trout.

Stocking of cutthroat began in the mid-1990s, and is limited to high lakes and headwater streams, Lewandowski said.

jromeo@durangoherald.com

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