- The Washington Times - Saturday, July 27, 2002

ANNAPOLIS Fish poison is the answer to ridding Maryland of those troublesome northern snakeheads multiplying in a Crofton pond, a panel of scientists officially recommended yesterday.

Tests conducted this week at the University of Maryland Center for Environmental Science in Oxford confirmed that the fish poison rotenone should effectively eradicate the Chinese fish from the pond.

Although scientists say all invasive species could pose problems to natural ecosystems, the snakeheads are particularly worrisome because they are top predators. If the fish proliferate, they could devastate native fish populations. Snakeheads are also tough to control because they can survive on land, breathe air and move slowly across damp surfaces.

In the tests, scientists placed dozens of juvenile snakeheads 2 to 4 inches long in aquariums containing water from the pond. The fish all died within 24 hours of being exposed to rotenone, a plant-based fish poison approved by the Environmental Protection Agency.

"If indeed we add the right effective doses to the pond, there's every reason to believe it will eradicate the little fish and the larger fish," said Don Boesch, the panel chairman and director of UMCES.

Earlier this month a local angler caught a 26-inch snakehead in the pond. The Department of Natural Resources said a Maryland man dumped a male and female snakehead in the pond two years ago and that the fish are apparently reproducing.

The panel's recommendations are subject to approval by DNR Secretary J. Charles Fox, who will announce a decision next week after leaving the matter open to public comments. DNR spokesman John Surrick declined to speculate when poisoning would begin, only saying it could be soon.

Rotenone is commonly used to control fish populations because it quickly and naturally degrades within days and poses no threat to humans, birds or other animals. The poison should be sprayed on the water's surface and injected underwater over the entire pond, the scientists said.

Dead and dying fish including those native to the pond that float to the surface should be quickly removed. The number and size of snakeheads should also be recorded before the remains are buried, the scientists said.

If they are available, some of the juvenile snakeheads should be placed in underwater cages in the pond during the rotenone application to verify that the dosage was lethal, the panel said.

About one week before the treatment, scientists should treat the water with herbicides to knock back the dense levels of aquatic vegetation, which includes waterlily, duckweed and watershield.

Before treating the pond with the chemicals, overflow barriers should be erected to minimize the risk of any rotenone or herbicide entering the Little Patuxent River, just 75 yards away.

After the rotenone treatment is complete, surveys should be conducted to determine whether any fish survived, the panel suggested. If so, another dose of rotenone should be applied.


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