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California Poisons Lake, Targeting Invasive Pike

California's Department of Fish and Game has begun poisoning Lake Davis, near the small Sierra Nevada community of Portola. The move targets the northern pike, an invasive species — but the gallons of poison will kill many other fish, as well.

In some parts of the country, the northern pike is a popular game fish. A bit bony and toothy, the fish puts up a good fight, which fishermen find rewarding.

California state wildlife officials have a different opinion of the fish. They are in midst a $17 million operation to poison the northern pike out of Lake Davis in the Sierra Nevada.


Officials say they want to prevent the pike from working down the water system, getting into the delta and killing endangered salmon. The state tried to eradicate the pike a decade ago by setting off explosions in the lake, electro-fishing and poisoning. It was highly controversial — and the pike came back.

No one knows exactly how the northern pike got from its native waters to Lake Davis, but most people figure they were brought in by someone from Minnesota or a local resident who missed fishing for the feisty pike. But in California, the fish are an unwelcome invader.

"They're a voracious fast-growing predator. We don't want them around," said Peter Moyle, a fish biologist at UC-Davis who specializes in invasive species.

Pike can get quite large and devour fish up to half their size — sometimes even waterfowl and small mammals.

Moyle points out that Lake Davis is in the Sacramento River watershed, which drains into the ecologically fragile Sacramento San Joaquin Delta. The delta houses numerous endangered species and supplies water to 25 million Californians. And that's not a good place for a top predator like the northern pike, Moyle said.


The California Department of Fish and Game tried to poison the pike out of the lake in 1997, but like the plot of a horror movie — 18 months later they were back with a vengeance. Since then, the state has tried electro-fishing, netting, even explosives. And now they're back to poison.

Beginning Tuesday, there will be two dozen boats on Lake Davis, pumping thousands of gallons of a fish-killing poison called rotenone into the water.

The poison will also be fed into miles of tributaries and ponds around the lake. Ed Pert, who is leading the pike eradication project, says the rotenone should knock out everything with gills: pike, trout, catfish, even aquatic bugs.

"There's no one that wants to put a bunch of chemicals in the water. I want to be clear about that," Pert said. "That's just something that we have to do because it's the last alternative that we have. No other alternatives will eradicate pike at Lake Davis."

The pike takeover has been nothing but trouble for the town of Portola just south of Lake Davis. The lake used to be Portola's drinking water source — until the first time the state tried to kill the pike with rotenone. Back then, hundreds of residents protested and the mayor even chained himself to a buoy to try and stop the poisoning. This time the opposition is muted and most have come to see it as necessary.

"It's been a long battle, a long long battle," said Sara Bensinger, owner of the Grizzly Store, a little bait and tackle shop right by the lake.

She rests against a counter in the hamburger stand she built next to her shop, back when times were good. She hasn't opened it for business in three years. She says the pike ate up Lake Davis's trophy-sized trout and drove away her customers. She can't wait until the pike are gone and the state restocks the lake with trout.

"Fish and Game has assured me that they're going to plant a ton of fish, big fish, little fish, in-between fish, fingerlings, all kinds of stuff," Bensinger said. "And life will be good all over again."

It will take a couple of years to know whether the operation was a success. One leading biologist describes it as a crapshoot. And if the pike do return, they're likely here to stay.

Fish and Game officials say this is their last best effort to eradicate the pike in Lake Davis, and in California.

Tamara Keith reports from member station KQED.

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