California Clearing Lake of Northern Pike Fish With Poison

By Anonymous

Northern pike, Esox lucius, are a normative invasive fish species that threaten California’s aquatic resources. California has been working to eradicate the fish from Lake Davis. The project uses a liquid rotenone formulation, CFT Legumine , to kill off the fish. After a recent successful treatment of the creeks flowing into Lake Davis, the California Department of Fish and Game (DFG) began a second stream treatment on September 24. The reservoir treatment occurred on the following two days. The reservoir was about 41,000 to 42,000 acre-feet at that time.

Releases from the dam into Big Grizzly Creek were shut off for five days when the reservoir treatment began. Plans then called for the dam to remain closed for up to 45 days to allow the rotenone formulation compounds to degrade naturally in the reservoir. DFG crews netted about 200 trout in Big Grizzly Creek immediately below the dam and moved them further down the creek so incoming springs could provide a sufficient habitat after flow from the dam was shut off.

About half the fish were eight inches or larger in size, and about two-thirds were brown trout and the remainder were rainbow trout.

After the first treatment in the creeks upstream of Lake Davis, several hundred dead pike were observed-mostly young-of-the-year, one-year-old fish and a few two-year olds. In some areas, pike were the only fish found, demonstrating how pike can dominate an ecosystem. This summer, DFG field crews did intensive electrofishing in the creeks to reduce the numbers of pike and help keep them from spreading further up the streams. Nearly 2,000 pike were removed by that control method.

Northern pike are top predators with long torpedo-shaped bodies built for speed. Their camouflaged coloration enables them to hide in aquatic vegetation and ambush their prey.

Once a pike is about eight inches long, it primarily feeds on other fish, which it grasps in its wide mouth. Pike are also highly fecund; for each pound of body weight, a female can lay 10,000 eggs.

The dead fish pose no danger to wildlife, such as herons and coyote, which scavenge in the area. The water is safe for wildlife to drink.

Copyright Compass Publications, Inc. Nov 2007

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