State neutralizes poisoned snakehead pond

Biologists believe all alien fish are dead

September 18, 2002|By Jackie Powder | Jackie Powder,SUN STAFF

Declaring that the northern snakehead fish has been eradicated in Crofton, state biologists applied a neutralizing agent yesterday to the largest of three poisoned ponds to rid the water of toxic chemicals added this month to kill the alien fish.

"We believe it's the end of the snakeheads in the pond, but we're going to come back again later this fall and do some additional sampling just to make sure," said state Department of Natural Resources spokesman John Surrick.

Since 15 gallons of the poison rotenone were sprayed on the ponds two weeks ago, state cleanup crews have recovered more than 1,000 dead juvenile northern snakeheads and six adults.

"What's left is monitoring to make sure that we've achieved what we believe we've achieved," Surrick said. "The pond was toxic for enough time that there wouldn't be any fish in it, and had there been any additional fish eggs there, the pond was toxic for long enough that they would have hatched and been killed."

The state poisoned the ponds on the recommendation of a panel of scientific experts that convened this summer to deal with the non-native fish. DNR officials were concerned that the fish - which can survive out of water for up to three days and slither short distances on land - would make their way to the nearby Little Patuxent River, multiply and devour native fish.

Scientists had expected the rotenone to decompose quickly, aided by warm water temperatures, but recent rain and clouds slowed the decomposition process.

Biologists with DNR's fisheries services applied potassium permanganate yesterday morning to the 4-acre Crofton pond to neutralize the poison, Surrick said. They will sample the pond today to determine whether the water quality has returned to normal.

DNR crews treated the middle-sized pond - measuring three-tenths of an acre - with the same chemical Monday night, and the water quality had returned to normal by yesterday morning, Surrick said. The poison in the smallest pond decomposed without the a neutralizer, he said.

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