When all is said and done, the upper reaches of Hermosa Creek, north of Durango, will have the largest continuous stretch of native Colorado River cutthroat trout in the state.

“In Colorado, we’ve got a religion that we need to bring back the natives,” said Buck Skillen, a member of the local chapter of Trout Unlimited. “And this is a big deal.”

The effort to restore Colorado River cutthroat trout in Hermosa Creek dates back to the early 1990s when wildlife managers used a natural waterfall on the creek’s east fork as a protective barrier.

Colorado Parks and Wildlife cleared out non-native species of trout – specifically brook, brown and rainbows – using a short-lived, organic poison known as rotenone. And in their place, it released Colorado River cutthroat trout, giving the waterway to the native fish for the first time in probably 100 years.

“And we’re going to work real hard to keep it that way,” Skillen said.

In the late 1880s, Western settlers fished the Colorado River cutthroat trout to the point of extinction. Then, to keep an important food source available, they dumped other species of trout into the cutthroat’s habitat.

The introduction of brook, brown and rainbow trout further exacerbated any chance of a cutthroat revival, because the fish is ill-equipped to compete with the invasive species, which take over rivers through predation and hybridization.

The magnitude of the cutthroat’s loss has never been truly quantified, but its range – which once spanned Colorado, New Mexico, Utah and Wyoming – was dramatically reduced, mostly because of habitat loss, overharvesting and competition with non-native species.

Clay Kampf, a fisheries biologist for the San Juan National Forest, said the best estimates show the Colorado River cutthroat trout is now found in about 14 percent of its historic natural habitat.

Facing the possibility of the U.S. Fish & Wildlife Service listing the Colorado River cutthroat trout as “endangered,” which would bring a host of restrictive protections, Colorado, Utah and Wyoming entered a three-state agreement to lead an aggressive reintroduction program.

“It works well for both parties,” said Jim White, an aquatic biologist with Colorado Parks and Wildlife. “This way, the states and local groups have more say in where and how to manage these fish. And it benefits the (Fish & Wildlife Service) because their resources are stretched pretty thin.”

In the last decade, the state of Wyoming has restored more than 60 miles of Colorado River cutthroat habitat, with most of that occurring in the upper Green River drainage by the town of Big Piney.

There, Mark Smith of the Wyoming Game and Fish Department said the population has been struggling since reintroduction. The fish haven’t spawned early enough, he said, which means they don’t grow big enough to survive winter.

“The turnaround hasn’t been as quick as we would have hoped, but we’re getting there,” Smith said. “We’re certainly making gains and going in the right direction.”

In Utah, the program has been wildly successful, with hundreds of miles of streams restored with their native species of trout, said Randy Oplinger of the Utah Division of Wildlife Resources.

Oplinger said Utah has been the most ambitious of the three states, likely because of the fact many projects are located on federal lands managed by agencies open to large-scale restoration efforts.

This year alone, the department plans to restore 75 miles of cutthroat habitat within the Colorado River basin. And Oplinger said trout populations tend to fair well throughout the river system.

“We started having a policy of go big or don’t do it at all,” Oplinger said. “And there’s still a lot of room for us to do more work.” The state of Colorado has started numerous restoration projects, and the effort is ongoing, resulting in about 890 miles of streams containing Colorado River cutthroat trout. But still, that’s only about 7 percent of its historic range.

Once a final barrier is constructed this summer on Hermosa Creek, just below its confluence with the east fork, an effort to dedicate more than 23 miles solely to the cutthroat trout will almost be complete.

Two decades ago, Hermosa Creek was recognized as an ideal place for a restoration project because of the creek’s outstanding water quality and because of its easy accessibility through Forest Service Road 578, which runs behind Purgatory Resort.

After the waterfall near Sig Creek Campground was used as a natural blockade from non-native intrusion in the early 1990s, two more human-made barriers were built in 2007 and 2013.

This summer, the U.S. Forest Service will begin construction on the final barrier at the Hermosa-east fork confluence to safeguard the waters above the blockade for the Colorado River cutthroat.

CPW’s White said that in the segments of the creek that have already been repopulated with cutthroat, population trends are encouraging. He said a recent sweep a few years ago found about 400 to 600 fish per mile.

“Populations above 400 fish per mile are usually ranked in the good to excellent category,” White said. “We’ve seen natural reproduction ... very shortly after that project on the main stem (of Hermosa) was completed.”

With a successful stretch of river returned to its native species, wildlife managers are expecting Hermosa Creek to get a lot of use from excited anglers.

As a result, a strict catch-and-release policy is on that section of river, White said, and there are other measures, such as habitat improvement and limiting bank erosion, that the agencies can take to protect the fish.

Andy McKinley, an employee with Duranglers, said anglers from all over the country come to this portion of Southwest Colorado to fish in Hermosa Creek’s waters.

“That’s a big draw for us, for sure,” McKinley said. “Some people put a big importance on catching native fish. I think it hearkens back to a time before mankind had a huge impact on the area.”

The quest to set right altered habitats continues to have strong cultural and ecological justifications, said Noah Greenwald of the Centers for Biological Diversity.

“We’re taking away what makes places like Colorado unique and special,” he said. “And we’re likely impacting other species when we replace a native with a non-native. It’s part of this larger extinction crisis.”

The Hermosa Creek restoration project is a coordinated effort between the U.S. Forest Service and Colorado Parks and Wildlife, as well as Trout Unlimited, which in total have spent more than a $1 million, Kampf said.

It will take a few more years for the waters upstream of the forthcoming barrier to carry only cutthroats, as non-natives still need to be removed, but Kampf said it will be worth the wait.

“I think the whole picture will finally be realized,” he said.

jromeo@durangoherald.com