Officials Seek to Protect Fisheries : Poison Poured in Lake to Kill Off White Bass

Starting at dawn Friday, California Department of Fish and Game crews began hosing 5,500 gallons of pesticide into Kaweah Lake, launching what experts say is the largest fish-kill operation of its kind in the state.

By mid-afternoon, tons of dead fish were floating on the surface of the lake, a flood-control reservoir that is tucked between the wrinkled brown foothills of the Sierra Nevada in Tulare County.

As the hot San Joaquin Valley sun beat down on the lake, crews worked from a dozen boats, dragging nets through the water, scooping up the kill they say was necessary if the commercial and sport fisheries in the Sacramento-San Joaquin Delta are to be protected.

Frustrated and Sad

Along the banks of the lake, hundreds of local fishermen stared at the dying fish flopping in the mud, frustrated by what they were witnessing, sad because there was no way they could stop what was happening.

“They’re killing our fish,” said Ray Bimap, 69, of nearby Woodlake. Standing beside him, R. M. Cook, 77, nodded, saying, “Bass fishing is about the only recreation we get around here.”

Poisoning the reservoir was the first step in a five-week effort by the department to rid the Kaweah and Tule river systems of all white bass, a voracious predator that experts say poses a serious threat to the delta, 150 miles to the north. Early next week, helicopters and ground rigs will begin spraying the pesticide rotenone along the Kaweah and Tule rivers and in the irrigation canals and farm ponds as far south as the Tulare Lake Basin.

Almost everyone, including officials of the major environmental groups, agree that poisoning the lake and streams is a radical but necessary step to eliminate the threat posed by the white bass.

“The . . . rotenone treatment in the Kaweah-Tulare Lake Basin is an unfortunate but necessary step,” according to the Environmental Defense Fund. The Sierra Club said that while it was not “enthusiastic about . . . an eradication program dependent on use of a toxic substance . . . the seriousness of the threat to the delta fisheries posed by white bass compels our support. . . .”

Supervisors Object

The only major objection to the fish kill came from the Tulare County Board of Supervisors. The board twice filed suit in an unsuccessful attempt to block the poisoning of the lake on the grounds that the state did not have the authority to conduct the project without the county’s approval.

The 150,000-acre reservoir, operated by the Army Corps of Engineers, is a popular fishing and boating spot for San Joaquin Valley residents. There are nearly 300 house boats moored on the lake and Corps reports show the area gets 650,000 visitor-days of use a year.

Revenues from the county’s 10% hotel occupancy tax and a 1.2% sales tax will be adversely affected, said Margaret Woodbury, a deputy county counsel.

She said, “They are going to put the lake out of commission for six weeks or more, then it will be two years before they restore the lake . . . and that will result in a substantial loss to the county.”

The white bass is a popular game fish in other states. The species--which grows to 16 inches or more and weights three or four pounds--is not found naturally in California. Biologists fear that if the voracious predator ever gets established in the Sacramento-San Joaquin Delta, east of San Francisco Bay, it would easily eat its way through the young salmon and striped bass populations.

$14-Million Loss

The loss of commercial and sport fishing income resulting from “an established white bass population in the delta could exceed $14 million annually,” the Department of Fish and Game’s environmental impact report concluded. That would amount to nearly one-fourth of the total income from commercial and sport fishing the delta.

White bass were brought into California experimentally by the department more than 20 years ago and planted in Lake Nacimiento, on the Salinas River. That coastal area was chosen for the experiment because the lake is isolated and the fish could not escape into other waterways, officials said. White bass were subsequently planted in Kaweah Lake illegally, they added.

“The white bass is a good game fish,” said Peter Moyle, chairman of the University of California, Davis, biology department and a leading fish expert. He is critical of the department’s initial decision to bring the fish to California because of the temptation to plant the fish illegally elsewhere.

“Somehow they appeared in Kaweah Lake; some bass fisherman threw them it, it’s an easy thing to do,” Moyle said.

Since the white bass was planted in Kaweah Lake, they have worked their way down the Kaweah River into a network of canals and stream courses that flow into the Tule River and the Tulare Lake Basin.

Drained by Farmers

Once a vast, shallow lake, the basin was drained by farmers who built levees and canals to contain and manage the waters so they could grow cotton and grain on the rich land.

The basin has no waterway connecting it to the north-flowing San Joaquin River. But state fish biologists fear that in very wet years, when the basin’s canals fill up, the white bass could swim north into the delta.

To prevent the bass from moving northward in the 1983-84 floods, the state built 24 fish barriers at strategic points along the rivers and canals, according to Nick Villa, the department’s white bass project director.

The state spends $600,000 to $800,000 a year to maintain these barriers, but they were only a temporary solution, Villa said. By poisoning the lake and the streams, killing off all of the white bass, the department hopes to solve the problem once and for all.

Rotenone, a pesticide made from the roots of the South American flame tree and other legumes, is the safest material to use, according to the department’s environmental impact report. The chemical blocks the fishes’ ability to extract oxygen from the water, causing it to suffocate.

“Rotenone has been used by the Department of Fish and Game for nearly 40 years without serious incident,” according to the environmental impact report. “The use of rotenone . . . does not present any identifiable or calculable public or environmental risks,” the report concludes.

Villa estimated the pesticide would kill 200 tons of fish. The fish, which will be unfit for human consumption, will be hauled to a rendering plant where the carcasses will be turned into fertilizers or other products, he said.

After the fish kill, the state will plant 120,000 catchable-size trout in the lake, along with bluegill and other warm-water fish.