National Hatchery Works on Restoration of Threatened Trout

Last month’s destruction of 300,000 Lahontan cutthroat trout infected with disease was a devastating blow to workers at the Lahontan National Fish Hatchery.

It was the first time in the facility’s 33-year history that such a massive extermination was required to control the spread of illness.

But fisheries experts hope future improvements will reduce the risk of disease and help them restore the threatened and popular sport fish to its historic prominence.

“Because we’re on a water reuse system we weren’t able to treat the bacteria,” said Larry Marchant, supervisor of the hatchery operated by the U.S. Fish and Wildlife Service.

Fish treated with antibiotics to combat furunculosis, caused by a bacterium found naturally in northern Nevada watersheds, developed a resistance to medication and were reinfected in the recirculated water.

Seventy percent of the hatchery’s operation is supported by recycled water. Only a small percentage of its daily water needs is available from fresh water pumped from wells, Marchant said.

After the diseased fish were destroyed, another 200,000 fish earmarked for planting this spring in Walker Lake, near Hawthorne, were moved into raceways fed by fresh water and are being treated with medicated food four to five times daily.

“They’re starting to do a little better now,” Marchant said of his patients.

Of the 17 federally owned production hatcheries in the West, Lahontan is one of four to use recirculated water. Marchant said he hopes to convert the facility to a fully freshwater system.

The change would require three new wells and the acquisition of water rights and land easements. The estimated price tag is $4.1 million, money that would have to be appropriated by Congress.

The hatchery raises 500,000 to 750,000 Lahontan cutthroats annually for stocking in area rivers and lakes. The rearing process, from egg to the time the fish reach about 7 inches in length and are ready for release, can take up to 14 months.

Each year before their release, tens of thousands of fish are implanted with a coded wire tag, a tiny magnetized wire no bigger than a thorn and thinner than a thread. The fish’s adipose fin is clipped to identify that it has being tagged.

After a fish is caught, biologists can track its age and movement.

“We try to tag about 20% of the fish we release,” Marchant said. “The main thing is survivability. We want to know the best size to release, the best locations to release.”

Native Lahontan cutthroat were prominent in the Truckee and Walker rivers, Pyramid Lake, Walker Lake and Lake Tahoe until the early part of this century, when numbers fell because of human encroachment on the fish’s habitat.

Once, the species was the largest trout in North America. The record sport-caught Lahontan cutthroat--a whopper weighing 41 pounds--came from Pyramid Lake in 1925.

The lake’s original population of Lahontan cutthroats became extinct 60 years ago. Other populations are listed as threatened under the Endangered Species Act, though they can be fished because of hatchery-production programs.

Today hatchery-raised fish in the lake grow to an average size of eight to 15 pounds--much smaller than historic natives.

Biologists at the Lahontan hatchery are intimately involved in research and efforts to restore the species to its previous grandeur. Since 1996 they have been harvesting eggs from Lahontan cutthroats found in a stream in the Pilot Mountains near the Nevada-Utah line and raising them at the hatchery.

The Pilot Peak brood stock, as they are called, “are the most genetically similar to the original Pyramid Lake strain of Lahontan cutthroats that we have,” said Fish and Wildlife spokeswoman Randi Thompson.

Workers at the hatchery incubate the eggs and carefully monitor their breeding to ensure genetic diversity. Each fish in the brood stock of about 200 is implanted with a “pit tag,” a tiny transmitter that allows biologists to identify each individual fish.

Marchant said they hope to collect about 100,000 more eggs from fish in the Pilot Mountains during the spawning run this spring.

“We’re hoping to make some of these eggs available for experimentation with egg incubation in the Truckee River,” he said.