RENO, Nev. (AP) - The U.S. Forest Service is proposing to eradicate trout from seven Sierra Nevada lakes in the Desolation Wilderness to help save the rare mountain yellow-legged frog.

"It's been done successfully in other areas," said Rex Norman, spokesman for the Forest Service's Lake Tahoe Basin Management
Unit. "It's a pretty well-proven technique and we're hoping it'll be effective here."

The frog, a candidate for listing under the Endangered Species Act, is no longer found at Tamarack, Cagwin, Ralston, Lucille, Margery, Jabu and LeConte lakes in the wilderness area west of Lake Tahoe, biologists said.

They hope getting rid of nonnative trout will restore the waters' once frog-friendly habitat, and the amphibians will make the leap from other areas in the nearby Eldorado National Forest.

"They are capable of moving on their own, and we prefer for them to do that," Norman said Thursday.

Until the 1960s, the Sierra Nevada population of the mountain yellow-legged frog was prevalent throughout the northern and central Sierra. Since then, biologists estimate its population has declined by as much as 90 percent because of nonnative fish stocking, disease, pollution and livestock grazing, according to the U.S. Fish and Wildlife Service.

Biologists say it takes up to four years for the mountain frog to complete its life stages from egg to tadpole to adulthood, which
leaves it vulnerable to predators like trout.

There were no fish in the seven alpine lakes before stocking of rainbow and brown trout to satisfy anglers began around 1950. Experts since have learned that the voracious fish are the frog's No. 1 enemy, and steps are being taken throughout the Sierra to remove nonnative trout from high elevations waters.

Among the targeted lakes, the last fish planting was in 2000.

Sarah Muskopf, a Forest Service aquatic biologist and project manager, said field surveys indicate many of the fish already may have disappeared over the past eight years.

"Some of the lakes, we think, have naturally become fishless on their own because they don't provide adequate spawning habitat or food," she said.

"I don't think any of the lakes we've selected have a huge fishery anyway."

Muskopf added that other lakes in the wilderness area will continue to be stocked for recreational fishing.

The Forest Service said no chemicals will be used to kill the fish. Instead, they will be trapped using gill nets that will be left in the lakes over the winter. Electroshocking will be conducted to stun and retrieve fish from streams and creeks. The dead fish will then be removed.

Biologists estimate it will take three to five years to remove all the fish from each lake, with the entire effort taking about 10 years.

The agency is soliciting public comment on the plan through Aug. 22.

(Copyright 2008 by The Associated Press. All Rights Reserved.)