Ag Weekly Online: Twin Falls, Idaho

KETCHUM, Idaho (AP) - Conservationists and fish biologists are hoping their recent efforts to make three irrigation dams on the Big Lost River more fish friendly will help bolster fish populations in the central Idaho stream.

In October, several conservation groups joined with the state to add fish passages to the diversion dams, to reconnect fish populations along several stretches of the river.

State fish biologists say the project should help trout. But they hope the biggest beneficiary is a species of whitefish unique to the Big Lost drainage.

Once prolific in the river, officials say the Big Lost mountain whitefish has declined to just 2 percent of its historic levels. A 2005 survey of adult fish estimated the total population at 2,745 fish.

The obstacles posed by the diversion dams have been singled out as a key factor in the fishery’s decline, Bart Gamett, a U.S. Forest Service biologist based in Mackay, told the Idaho Mountain Express.

The Idaho Department of Fish and Game issued a restoration plan for the whitefish in May 2007. It set a goal of establishing two distinct populations of mountain whitefish, one above and another below the Mackay Dam, each with at least 5,000 fish.

This fall, volunteers led by Trout Unlimited retrofitted three diversion dams with fish ladders and bypass channels. Officials say the ladders and bypasses will help whitefish move out of sections of the river that become uninhabitable and migrate to spawning areas.

Unlike trout species, Gamett says whitefish can’t jump, which hurts their ability to get past the diversion dams, small vertical drops or other barriers as they head upstream.

Others involved in the work include the Big Lost River Irrigation District, the U.S. Forest Service, Natural Resources Conservation Service, and several area landowners.

Information from: Idaho Mountain Express, http://www.mtnexpress.com

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