"That should catch any snakeheads or eggs," said Doug Redmond, a natural resources specialist for the commission.

It will take about two days and cost about $10,000 to drain the lake and -- if rainfall doesn't speed up the process -- about two weeks to refill it, officials said.

The work attracted small crowds throughout the afternoon, including Jan Bachman, a fisherman who lives five minutes by car from the park in Wheaton.

Bachman said that the lake has become a source of trout for him in the past two years and that it angers him that someone dumped a snakehead in it. He said the snakeheads' ability to gobble up other fish and destroy fisheries is widely known.

"I think somebody's trying to create a fishery for snakeheads," Bachman said.

Federal officials banned the importation and interstate sale of snakeheads in 2002. But people continue to sell them privately on the Internet and in pet shops.

Emergency ban

Duncan's emergency ban on selling or possessing snakeheads is expected to go into effect when he signs the measure next week. It will expire in 90 days unless approved by the County Council, according to a county spokeswoman.

The measure will subject anyone who owns a northern snakehead to a $1,000 fine and up to six months in jail. County snakehead owners are asked to turn in their fish by calling 301-650-2890.

"You can't have one on a leash either," Duncan told reporters.