DURANGO, Colo. (AP) — A decades-long effort to restore the Colorado River cutthroat trout to the upper reaches of Hermosa Creek has been completed, resulting in the largest continuous stretch of waterway for the native fish species in the state.

“This is a 35-plus-year vision come true,” said Jim White, an aquatic biologist with Colorado Parks and Wildlife.

After Western settlement in the late 1880s, the Colorado River cutthroat trout were fished to the point of extinction. Then to make matters worse, settlers dumped other, more competitive species of trout into the cutthroat’s habitat.

All of the factors – habitat loss, over-fishing and competition with non-native species – led to a dramatic decline in the cutthroat’s historic range, which once spanned Colorado, New Mexico, Utah and Wyoming.

Some estimates show cutthroats are now found in just 14% of their historic natural habitat.

As a result, over the years, there’s been the possibility of listing the cutthroat on the U.S. Fish & Wildlife Service’s endangered species list.

Wanting more local control and less restrictive federal regulation, however, three states – Colorado, Utah and Wyoming – entered an agreement to lead an aggressive reintroduction program to avoid the endangered species list.

The upper reaches of Hermosa Creek were instantly recognized as an ideal place for a restoration project, both for its outstanding water quality as well as easy access through a Forest Service road that runs behind Purgatory Resort.

Over the years, barriers have been installed to isolate certain stretches of water and an organic poison known as rotenone has been used to clear out invasive species, like brown, brookie and rainbow trout.

All this to clear the path for cutthroat reintroduction.

CPW recently stocked an estimated 4,000 cutthroat fingerlings and an additional 475 mature cutthroats in the final stretch of the Hermosa Creek project, giving the waterway back to the native fish for the first time in 100 years.

And now, the project to restore 23 miles (37 kilometers) of cutthroat habitat is finally complete.

“We’ve worked piecemeal to get to this point,” White said. “And this is the final project area that’s been completed.”

There is one caveat, White said: Hybridized rainbow trout were found after the application of rotenone, and though wildlife officials believe they have since removed the fish from that stretch of the creek, it will be necessary to keep monitoring it.

“We’re not confident where the (hybridized rainbow) came from,” he said. “We’re going to monitor ... for the foreseeable future.”

If the hybridized rainbows start showing in increased numbers, it may be necessary to treat the stretch of water again, White said.

For the stretches of upper Hermosa Creek that have been restocked with cutthroats, populations are showing encouraging signs. White said there are about 400 to 600 fish per mile, which he called a “nice, healthy population.”

Because the area is a popular draw for anglers, there is a strict catch-and-release policy. Local fish-guiding companies have said in the past that anglers come from all over the country to fish native cutthroats.

The Hermosa Creek project was a collaboration between CPW, the U.S. Forest Service and Trout Unlimited.

Buck Skillen, with the local chapter of Trout Unlimited, said the organization has contributed countless volunteer hours over the last 15 or so years in this reintroduction effort, as well as provided funding.

“We stand ready to assist our partners, CPW and USFS, in on-going habitat improvement and stabilization efforts that will contribute to the safeguard of our cold water fishery in this very special place,” he said.

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