Anglers help with whirling disease study

By Cherry Sokoloski
North Forty News

This summer, anglers at Parvin Lake near Red Feather Lakes can try their hands at doing aquatic wildlife research--or at least they can be research assistants. While at their "job," fishermen have a chance to catch some nice rainbows in a beautiful setting.

Parvin Lake is home to a Division of Wildlife research station, which is the hub of DOW efforts involving whirling disease. Run by fishery and wildlife biologist George Schisler, the station is experimenting with different varieties of Hofer-cross rainbows, fish that are extremely resistant to whirling disease.

The station, along with the DOW research hatchery in Bellvue, has achieved remarkable success with its research, which is aimed at reestablishing healthy, naturally reproducing rainbow trout populations in Colorado.

Parvin is being used as a "trial" lake for six different varieties of Hofer crosses. Last summer, 12,000 fingerlings (4- to 5-inch fish) were stocked at the lake. This year, the DOW wants to determine which of the Hofer strains have survived best--and which are being caught by fishermen. "It will help us make decisions on which varieties should be used in the future," explained Schisler.

With fingerlings, there can be a high mortality rate from predators such as birds, fish-eating mammals or other fish. But many do live through the winter. Last year's stockers will measure about 8 inches long this spring, and they'll grow as the summer progresses.

The Hofer crosses are significantly larger than Colorado River rainbows of similar age. At maturity, some of these crosses can weigh more than 5 pounds.

How to help

Helping with the research is pretty simple. The DOW wants fishermen to check in at the Parvin Lake check station when they arrive at the lake and when they leave, at which time they can report their catch. The agency is interested in the fishing experience, even if the angler got skunked that day. "All the information is important," noted Schisler.

If the station is not manned, fishermen may sign in and out using the logbook at the entrance to the lake.

The Hofer-cross fingerlings were tagged with tiny coded wires before planting. Fishermen will not be able to see these tags, since they are embedded in the nose of the fish, under the skin. However, a special scanner can determine if the fish has a tag - and if so, which variety of Hofer cross it is.

If a fisherman keeps fish, it is important to let the check station attendant examine the fish for tags. After scanning, anglers get to keep and eat the fish. Keep in mind that bait is not allowed at Parvin Lake, and there is a two-fish limit.

Research successes

The Parvin station and Bellvue Research Hatchery, along with several other labs in the country, have been working for several years to develop strains of whirling disease-resistant rainbows that can not only survive in the wild, but also reproduce. Because whirling disease attacks "fry," or young fish, it was not possible for Colorado River rainbows to successfully reproduce once the disease arrived in Colorado. As a result, wild populations of rainbows in the state were virtually wiped out by the disease.

As part of the current research effort, disease-resistant Hofer rainbows were brought from Germany a few years back. The Parvin Lake station has been crossing Hofers with various types of rainbows in an effort to create a fish that is viable in Colorado waters.

Interestingly, Hofers were originally exported to Germany from the United States, perhaps from the Gunnison River in Colorado.

Beginning in 2004, the DOW stocked Hofer crosses in several Colorado rivers. Recently, researchers have had the satisfaction of finding the first evidence of successful reproduction in the wild. Fry samples were taken from the Gunnison River last fall, and researchers--using genetic markers--found significant numbers of Hofer-cross offspring.

"We are confident that natural reproduction is occurring from the fish we stocked there in 2005 and 2006," said Schisler. Additional sampling will occur this year on both the Gunnison and Colorado Rivers.

Anglers who test their skills at Parvin Lake this summer can boast that they are part of an important project, one that's making it possible for rainbows to live and breed in Colorado waters once again.