Just before dawn on October 15, 1997, four people wearing wet suits waded into Lake Davis in California’s northern Sierra mountains, swam out 100 yards and chained themselves to a buoy. The crowd that gathered on shore in the dark raised candles in solidarity with the swimmers and in silent protest against the grim action scheduled to begin at daylight.

State fish biologists arrived on cue dressed in coveralls, gloves and facemasks. Ignoring the demonstrators, they began pumping chemicals into the lake, a seasonal water supply for the city of Portola. The biologists’ mission was to kill northern pike, a voracious nonnative species that had been illegally introduced to the lake. By noon, pike and trout, carp and frogs floated belly up on the lake’s surface.

Chemical treatments like the one at Lake Davis are by no means unique. Every autumn, fish biologists don protective gear to dump thousands of gallons of chemicals into streams and lakes around the West. After a half-century, poisoning public and private waters has become a seasonal rite as predictable as spring spawning.

From the Colorado Rockies to the Sierra Nevada, wildlife managers have come to rely on rotenone, an organic pesticide, to improve sport fishing for anglers and to protect native species threatened with extinction by invaders. The operations range from two-pound applications in pools on remote mountain streams to the 878,000 pounds of rotenone dumped into Strawberry Valley, Utah, to remove chubs and suckers competing with anglers for rainbow trout and other game fish. Along with promoting the sport fishing industry, anglers credit rotenone with rescuing the Apache cutthroat trout in Arizona, the greenback trout in Rocky Mountain National Park and the Lahontan cutthroat trout in Nevada. Chemical treatment has been so widely accepted over the years that poisoning entire lakes has hardly raised a public eyebrow.

Lately, however, rotenone has begun generating opposition from scientists and the general public. In an era of eroding trust in government, some are challenging the effectiveness of a procedure that is time and labor intensive and generally requires repeated treatments. Others are condemning chemical eradication altogether, calling it “management by death,” an indiscriminate killing of species, both vertebrates and invertebrates. A growing number of critics—including opponents of the Lake Davis poisoning—worry about the unknown health effects of chemicals in their drinking water.

As public values shift from preserving individual species to protecting entire ecosystems, many are questioning the long-term effects of management by chemicals and the merit of using them at all.

“Fish managers have never thought about whole ecosystems or about what they are harming in their management of specific fish,” says Nancy A. Erman, a specialist emerita and aquatic ecologist at the University of California, Davis. “They just go on wiping out the food for everything that depends on an aquatic system, ignoring the other species that have evolved.”

Fish biologists devoted to preserving native species defend the use of rotenone as a lesser evil than extinction. Phil Pister, known as the father of native fish restoration in America, has spent decades in the Sierra Nevada trying to rescue the golden trout, California’s state fish. Left alone, hybrids of golden and rainbow trout would breed with the pure strain, contaminating the population and launching the golden trout toward a listing under the federal Endangered Species Act.

That would be a biological calamity, says Pister, a retired California Fish and Game Department biologist who is founder and executive secretary of the Desert Fishes Council based in Bishop, California. Preventing it justifies drastic measures.

“Rotenone is the final tool—the one you use when nothing else will work,” he says. “A whole bunch of native fish literally would not exist but for rotenone.”

But once-isolated voices like Erman’s are growing louder. They became an earsplitting chorus at Lake Davis despite public concern about the demise of the local trout fishery to the cravings of northern pike. The predatory pike, a native of midwestern waters, first surfaced in 1994 in the lake, fifty miles northwest of Reno, Nevada. Without action, fish biologists believed pike would make their way downstream through the Feather River into the Sacramento and San Joaquin rivers. There, officials feared, their voracious appetite for smaller fish would destroy California’s multimillion-dollar commercial fishing industry. The state’s $2 million plan aimed to poison the pike and all of the other fish in Lake Davis, then replant the lake with rainbow trout.

Local residents fought the plan in court and out. Although most were as eager as state officials to get rid of the pike, they were worried about the poisoning’s effect on tourism, the mainstay of the rural economy. Mainly, however, they were alarmed about chemicals in their seasonal water supply. No one wanted to drink Lake Davis water after it had been pumped with enough chemicals to kill all the fish, says Portola Mayor Bill Powers, one of the four protesters chained to the buoy.

The chemical treatment of Lake Davis went badly. Poisons leaked downstream into Grizzly Creek, killing fish throughout a five-mile stretch of stream. In the lake itself, the chemicals that officials promised would completely dissipate within two months lingered for ten. The California Fish and Game Department was fined $250,000 by the regional water quality board, and state legislators eventually authorized $9 million in reparation payments to Portola, Plumas County and local residents and businesses harmed by the project.

That, however, did not end the ordeal. Northern pike resurfaced in Lake Davis last spring, probably survivors of the rotenone treatment. By fall, state officials admitted that the more than 200 young pike they had netted were generated by adult pike spawning in the lake.

The debacle of Lake Davis has become a rallying cry for other western communities fighting the use of rotenone in local streams and lakes. In the southwestern Montana town of Three Forks, opponents have used the California experience to protest a project that managers say will help native westslope cutthroat trout. Biologists want to put ten gallons of liquid rotenone in Cherry Creek, which drains into the Missouri River. The fish’s competitor, the Yellowstone cutthroat trout, is nearly identical to its westslope cousin but is native to streams that flow into the Yellowstone River. Both species appear on Montana’s list of species that merit special concern. After conducting an environmental review for the project, biologists determined that the only significant impact would be removal of a nonnative species and replacing it with a native fish, says Pat Clancy, a Montana fish biologist and Cherry Creek project manager.

But opponents say the project violates clean water regulations. They claim in their appeal that the federal Clean Water Act and Montana water laws prohibit the discharge of any pollutant in concentrations great enough to harm a species. Fish eradication projects around the state have historically ignored these regulations, says Alan Joscelyn, a Helena attorney who filed the appeal. He questions how well government agencies in any state have thought through the long-term ramifications of their rotenone projects. “Lake Davis raised the question of alternatives to poison and how these projects fit into the larger framework of management for other species,” Joscelyn says.

Clancy counters that Cherry Creek is one of the few places in the state where it is feasible to replace an introduced fish species with a native species. The stream is protected from most invaders by waterfalls downstream and still has the habitat to sustain a healthy population of westslope cutthroat trout. The value of the biological diversity that stands to be gained easily justifies using ten gallons of rotenone. Without the chemical, preserving the westslope cutthroat would be nearly impossible, he says.

“It’s a matter of magnitude. When you’re trying to conserve a native species in peril of going extinct, I don’t see why we shouldn’t use chemicals,” Clancy says.

In most places, however, it’s not a matter of using rotenone one time and forever protecting a threatened native fish. The vast majority of cases require repeat applications. Fish managers have not always been honest about how often rotenone must be applied, says Mike Kossow, founder of Meadow Brook Conservation Associates in Taylorsville, California. And they have been less than straightforward about the effectiveness.

“Rotenone generally fails to eradicate nonnative species. It never gets rid of them all and it never keeps them gone,” Kossow says.

Pister’s golden trout restoration program on the Kern River in the Sierra Nevada has been relying on rotenone for more than three decades. The largest current threat to the native fish is a hybrid strain that carries the genes of nonnative rainbow trout. If the hybrids breed with the pure strain, California and the world will likely lose the golden trout—a beautiful fish that seems to glow through the water.

It is the U.S. Forest Service that has forced a delay in the latest poisoning plan. The agency manages the Golden Trout Wilderness, the trout’s native habitat, and must approve the use of rotenone. Inyo National Forest officials have insisted on completing an environmental study before deciding whether to authorize the project, which is backed by the U.S. Fish and Wildlife Service and California’s Department of Fish and Game.

“We don’t want to dump poisons into a stream in a wilderness area unless we fully understand all the effects,” says Matt Mathes, a Forest Service spokesman in California. “We don’t want to get so focused on one species of trout that we overlook the effects on other organisms, down to microorganisms.”

Even those who endorse rotenone are critical of the way agencies have used it. “It’s an easy way out,” says Robert Behnke, a fisheries biology professor at Colorado State University. “They use it instead of finding creative ways to manage fish populations.”

Despite his dedication to preserving the golden trout, Pister, too, is cautious about endorsing the use of chemicals in natural systems. Aquatic ecologists like Erman are legitimately concerned that “in our zeal to protect one species we wipe out another,” he says. And he shares some of the criticism of the rotenone project at Lake Davis. But Pister bristles at direct comparisons between the Lake Davis and Kern River projects. The pike eradication used 16,000 gallons and 64,000 pounds of rotenone. The golden trout protections call for fewer than ten gallons of chemicals.

“It’s like comparing World War II to an outbreak somewhere in the Sudan,” Pister says.

Still, rotenone is designed to kill all aquatic life. Its indiscriminate quality has prodded managers in Great Smoky Mountains National Park to seek alternatives for protecting native fish. Although rotenone was used in the park many years ago, biologists today have chosen mechanical methods to restore the native brook trout. They have spent days—even weeks—electroshocking streams and netting the stunned fish. They replace the unharmed brook trout and remove the nonnative rainbow and brown trout.

Along with brook trout, the primary beneficiaries of electroshocking are the native nongame fish—dace, sculpins and stonerollers, says Bob Miller, a park spokesman. “Rotenone tends to kill not only the target species but every other species in there,” he says.

But park officials are planning to use rotenone on several small sections of stream where such species are absent. Increased acid in creeks, primarily from air pollution, is reducing the areas where brook trout can survive. Park biologists feel pressure to maintain the habitat wherever they can, Miller says. It’s a small portion of the national park’s waterways. Of the 730 miles of stream within the park, fewer than twenty miles have been restored.

Fish managers would have fewer problems protecting native species if they had exercised more foresight in the past, says Erman, the UC Davis aquatic ecologist. Rotenone is being used to solve problems caused by government agencies’ own exotic fish planting programs. The invasive species they now poison to restore native species are often the very species they planted to enhance sport fishing in previous years, she says.

“Agency fish managers need better ecological education. I hope they will become more enlightened, but I’m not sure they will,” says Erman.

Pister says it’s not as simple as better education. Human tinkering with ecosystems has created complex natural resource dilemmas. The attempt to solve some of those dilemmas has spawned the rotenone controversy. In reaching his own determinations about whether to poison or not to poison, Pister turns to Aldo Leopold, the father of American conservation ecology.

“Leopold said a thing is right when it tends to preserve the integrity, stability and beauty of the biotic community,” Pister says. “It is wrong when it tends not to. That’s the ethic that underwrites all resource management.”