STORY - Wyoming's oldest operating fish hatchery is getting an upgrade that should be complete in about a year, a change that could result in more of a prized trout species appearing in the state's alpine waters.

Since 1906, the Story hatchery has drawn water from a spring fed through a half-mile of caverns connected to South Piney Creek, said Steve Diekema, superintendent of the Wyoming Game and Fish Department facility.

The protected water supply had always been considered an asset to the hatchery until South Piney Creek tested positive for whirling disease several years ago, Diekema told a group visiting the facility earlier this week as part of the Governor's Natural Resource Tour.

The annual two-day educational field trip is organized by the Wyoming Department of Agriculture as a way to highlight successful programs and projects in counties around the state.

Whirling disease is caused by a parasite that infects salmon, trout and whitefish, causing them to swim erratically, sometimes "whirling" in circles. Young fish are especially susceptible, and can die from the disease or become vulnerable to predators.

Diekema said the hatchery had regularly tested its fish for the disease, knowing the parasite was present in South Piney Creek. After fish at the hatchery tested positive in 2005, the department had to destroy 80,000 trout.

Though a combination of filtration and ultraviolet radiation could kill the parasite in incoming water supplies, that option is impractical because of the heavy silt present in the hatchery's water supply, he said.

Instead, the hatchery has been reconfigured as a brood stock facility, supplying trout eggs for use in other waters free of the disease. The Legislature appropriated $2.6 million in 2006 to rehabilitate the facility for brood stock operations.

Adult trout are usually less susceptible to infection with whirling disease, and typically show milder symptoms when afflicted. They do not transmit the disease to eggs, Diekema said.

And though the parasite, which doesn't harm people, could return to the water at the Story hatchery, trout typically can't contract whirling disease until they are at least two days old, making the Story eggs safe for hatching in disease-free waters.

Diekema said renovations should be complete by the fall of 2009, after which the Story hatchery will annually produce 1 million lake trout eggs, 500,000 brook trout eggs, 2.5 million rainbow trout eggs and eggs for 300,000 splake, a cross between a lake trout and a brook trout.

Hatchery managers also plan to oversee production of up to 50,000 golden trout eggs, Diekema said.

"A lot of the golden trout eggs out there aren't genetically pure," he said, so Wyoming is looking to breed its own eggs for stocking lakes at high elevations with the rare trout.

The finicky, elusive fish are most commonly found in Wyoming in the Wind River Range.

Fisherman often travel long distances to remote areas to fish for golden trout, which are native only to the Sierra Mountains in California, he said, adding that golden trout egg production has proven difficult at those hatcheries where it has been tried.

"We think we can do it," he said.