WADSWORTH, Nev. (AP) -- State and federal biologists and a local tribe are releasing 50,000 Lahontan cutthroat trout into the Truckee River in the final phase of a five-year study aimed at helping to save the fish from extinction.
Lahontan cutthroats 40 pounds or larger once migrated 100 miles from Pyramid Lake in the high desert northeast of Reno to the alpine waters of Lake Tahoe.
That was before their spawning route was blocked by the Derby Dam in 1905, the cornerstone of the first major irrigation system in the West.
The native fish, now protected as threatened under the Endangered Species Act, disappeared from the river and Pyramid Lake by the end of World War II.
But the Pyramid Lake Paiute Tribe has been raising the cutthroats in its hatchery at the lake near Nixon, Nev. The state and federal governments in recent years have been taking strides to reintroduce the fish to the Truckee River, which passes through Reno on its way down from the Sierra Nevada.
''The habitat seems to be improving. We've neglected it for so many years it's nice that people are concerned,'' said Kim Tisdale, western regional fisheries biologist for the Nevada Division of Wildlife.
The Bureau of Reclamation is developing plans for a fish ladder or other passage system around Derby Dam about 20 miles east of Reno. But other small dams and diversions still block the route to Lake Tahoe, including a power-producing dam at Verdi just west of Reno.
To learn more about how the hatchery-reared cutthroats respond to the river, the U.S. Fish and Wildlife Service and the state have released 50,000 young fish into the Truckee in each of the past four years.
Another 50,000 of the eight-inch, year-old cutthroats are being released this year -- 10,000 on Wednesday near Wadsworth and 10,000 more Thursday near Painted Rock. The other 30,000 are to be released next week in Sparks, Reno and Verdi.
The tribe contributed all the fish from its hatchery this year after a disease caused a massive fish kill at the Fish and Wildlife Service's hatchery at Gardnerville earlier this year.
''We're trying to assess the habitat and learn more about migration patterns,'' said Elwood Lowery, executive director of the tribe's fisheries program.
The four year's of releases so far have taught scientists that the fish are determined to move upstream in search of better habitat with shaded banks and cooler waters.
That means passage around existing dams likely will be important to overall recovery efforts.
''As far as the recovery of the fish, fish passage is imperative,'' John Branstetter, a fishery biologist for the Fish and Wildlife Service in Reno.
''The fish are going to have to get upstream to find some suitable habitat,'' he said. ''We are going to have to start dealing with some habitat problems. We've got a lot of open areas where there used to be a cottonwood canopy.''
The other major hurdle facing the cutthroats appears to be competition from brown and rainbow trout. Those two species have been stocked in the river for years and tend to feed on the young cutthroats.
''It's very difficult for cutthroats to compete with those other fish in these circumstances,'' Branstetter said.
Meanwhile, the tribe is focussing its efforts on hatching hundreds of thousands of eggs in tanks filled with well water along the Truckee River in an effort to place an imprint on the fish that will cause them to return upstream to spawn, rather than returning to areas near the hatchery where most hatchery fish consider home.
''You can put as many fish in the river as you want and not make a difference because they are hatchery-reared fish. We need to rear them on the river,'' Lowery said Thursday.
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