- Associated Press - Saturday, June 27, 2015

DENVER (AP) - If the Brothers Grimm ever wrote a fable about a fish, the rainbow trout surely would have been cast in the lead role.

The shimmering salmonid brightly colored in green and red was long the star of Western fishing dramas, a handsome champion rising to an angler’s offering and leaping skyward with the nimble agility of an athlete in its prime. Although originally transplanted from the Pacific Northwest, the fish established themselves in Colorado long ago, eventually evolving into their own strain recognized, for a time, for its hardiness.

Name alone served as an icon enough to attract anglers eager to discover their own Rocky Mountain rainbow.

“People definitely associate rainbows with the West,” said Greg Felt, a veteran fishing guide and co-owner of Ark Anglers fly shop and guide service in Salida and Buena Vista. “It’s a magical-sounding name, like a unicorn - ‘rainbow’ trout.”

Much like the mythological unicorn, though, Colorado’s rainbow trout pulled a disappearing act about 20 years ago. The black magic known as whirling disease decimated the state’s rainbow trout population, reducing it to less than 1 percent of the total trout population in former strongholds such as the Colorado River in the mid-1990s.

With fish hatcheries and rivers statewide soon testing positive for the parasite responsible for whirling disease, the outlook grew increasingly grim. But the tumultuous story may have finally found its fairy-tale ending.

“It’s been a long road, but bringing back populations of fish that were essentially extirpated from Colorado can only be called a huge success,” said George Schisler, Fort Collins-based aquatic research team leader for Colorado Parks and Wildlife.

Like so many fairy tales, the rainbow’s current reality show traces its roots to Germany. It was there that a family named Hofer realized it had established a strain of rainbow trout resistant to the parasite that otherwise infects young fish. The infection deforms the fish’s spine, causing the fish to swim in a whirling pattern, thus the name.

Infection is a virtual death sentence to fish, yet the parasite survives to infect others. When whirling disease hit Colorado’s rivers, natural reproduction of rainbow trout virtually ended. And even a costly, eight-figure cleanup of Colorado’s entire hatchery network could do nothing to restore wild, stream-bred rainbow trout.

Almost overnight, brown trout, which are resilient to the disease, became the dominant sport fish of Colorado.

“People like the opportunity to catch multiple species of fish,” said Felt, whose hands-on experience as a guide is corroborated by CPW angler surveys. “Especially for people new to fishing, brown trout may be something they need to learn a little more about. So variety, a mix of fish is really good for people to experience.”

That experience has grown increasingly more accessible since German researcher Mansour El-Matbouli presented data on the Hofer strain at a Denver conference in 2002. CPW quickly began importing rainbow trout eggs from Germany, eventually crossbreeding them with Colorado River rainbows in an effort to instill more wild characteristics into the otherwise docile hatchery trout. Hofer rainbows have also been crossed with lake-adapted Harrison rainbows from Montana to bolster populations in Colorado lakes and reservoirs.

By 2006, Schisler had established the Hofer’s disease resistance in local reservoirs and in 2010, fingerlings were stocked in the Colorado River near Hot Sulphur Springs. Fourteen months later, researchers returned to find a good number of 15-inch rainbows and evidence that young fish were hatching in the wild.

Since then, CPW biologists have been stocking fingerling Hofer-crosses throughout the state at different sizes and times of year to optimize survival. After 15 years of brown trout dominance in most Colorado rivers, presto! The rainbow has returned. Anglers are once again reporting healthy rainbow catches in the upper Colorado, Rio Grande, upper Gunnison, Poudre, East, Taylor and Yampa rivers, even places like the Arkansas that were never considered major rainbow trout fisheries.

“The introduction of the Hofer-cross strain has definitely had some positive impacts on the character of the fishing here,” Felt said. “They are just a different fish altogether, and given some of the conditions we deal with on the Arkansas, they are apt to achieve a larger size over the course of their life than the browns are.

One of the things I’ve come to appreciate is that the rainbows help diversify the character of the fishery and the experience. They tend to be more active at times and in places when browns might not be. Since they’ve been introduced, it’s made more of the river and more of the year productive. It’s a fun thing.”

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Information from: The Denver Post, http://www.denverpost.com

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