Red Feather Lakes
If you appreciate the notion of using old resources to solve new problems, you’ll love the current happenings at the Colorado Division of Wildlife’s venerable Parvin Lake Research Station. This is the story of how a place that time – and the wildlife establishment – forgot now contains the seeds for the revival of a vital part of Colorado’s trout resource.
After two decades in the aquatic equivalent of mothballs, the once-ramshackle facility fairly hums as the hotbed of research that promises to re-establish the state’s supply of stream-bred rainbow trout.
The story of how a rainbow strain developed resistance to whirling disease during more than a century of evolution in a hatchery in Germany already has been told on these pages. What’s new is how the Division of Wildlife dusted off its old Parvin facility as the centerpiece of a program aimed at restoring a treasured sport fishing component.
Since its unfortunate introduction during the late 1980s, whirling disease almost totally removed naturally occurring rainbows from most Colorado streams. The Parvin project, in a few short years, could bring them back. Rivers that once teemed with wild, thick-shouldered rainbows – the Colorado and Gunnison quickly come to mind – again might sport lots of trout with pink side panels.
“Our goal is to create fish that reproduce in the wild,” said George Schisler, DOW biologist who is leader of a thrust that ultimately might change the way the entire nation deals with WD.
Star performer in this drama is the Hofer rainbow, named for a German hatchery and celebrated for a resistance to WD similar to that of brown trout, an indigenous European species that evolved with the malady. Trouble is, the Hofer strain is highly domesticated, trout poultry if you will. Lacking fright response, it has limited ability to survive and reproduce in a natural environment.
Thus we have Schisler’s challenge: to develop a closely manipulated hybrid representing the best of both breeds. That’s where the Parvin facility, dark since the early 1980s, comes into play.
“We needed a place to expose the offspring of these crosses to whirling disease away from any of our active trout-rearing facilities,” said Schisler, who specializes in such pioneering research ventures. “Parvin gives us the ability to conduct a large research project. It’s a powerful tool.”
Without drowning in the many intricacies, it’s enough to know it generally involves blending the milt from the highly susceptible Colorado River rainbow stock with eggs from a female of the Hofer strain. Predictably, a certain percentage of the offspring retain a resistance to the disease.
The notion is to select these resilient specimens through successive generations of hybrids to produce a fish that exhibits the wild characteristics of the CRR, along with a certain immunity to WD.
Schisler also is experimenting with other wild rainbow strains, along with native Colorado cutthroats. Official results from an exposure of second-generation fish using a three-fourths CRR mix is pending, but the biologist can read the signs.
“Some will inherit the resistance, others won’t,” he said. “That’s pretty obvious looking at the family patterns.”
The experiment will produce 2-year-old adults next spring, from which will emerge another generation of hardy trout.
“A true test is when we see natural reproduction from these crosses,” Schisler said. “That would come in the third generation.”
As for the wild characteristics, the first generation of Hofer hybrids begins to show some evidence of fright; the second become highly skittish.
A separate test involves placing fish directly in the Gunnison Gorge, where a once-thriving population of trophy rainbow has been decimated by WD. The trial involved 10,000 pure CRR and an equal number of 50/50 hybrids, all of a size – 4 1/2 to 6 inches – at which they are impervious to the disease.
Oddly, neither survived well, a result Schisler attributes to predation from the large brown trout that occupy the niche vacated by rainbows. In fact, this balance between reintroduced rainbow and the now-dominant browns is one of the technical and political issues the wildlife agency must address as the process continues.
Yet another benefit of the Hofer variety may reside in its high growth rate, which may exceed those types currently used in DOW’s expansive put-and-take stocking operation. The agency has begun tests to determine relative desirability of various crosses.
Meanwhile, the potential of a wild rainbow strain recently discovered in a German stream has stateside biologists drifting off into sweet daydreams of a super trout that might render all these machinations unnecessary.
But until this uber-trout can be imported and proved true, the Parvin antique hums along as the unlikely center of a trout research universe no one could have imagined short years ago.
Listen to Charlie Meyers at 9 a.m. each Saturday on “The Fan Outdoors,” radio KKFN 950 AM. He can be reached at 303-820-1609 or cmeyers@denverpost.com.
