Snakehead fish are increasing their populations in tributaries of the Potomac River, biologists say.
Fisherman have caught twice as many of the air-breathing, land-walking fish this year as in all of 2006, said John Odenkirk, fisheries biologist for Virginia's Department of Game and Inland Fisheries.
"This year alone, there have been 40 counted," Mr. Odenkirk said.
Snakeheads have been dubbed such ominous nicknames as "Frankenfish," "killer fish," "pit bulls with fins" and "Chinese thug fish." Research showed that northern snakehead fish eat other fish, can walk on land and can live out of water for three days.
The fish, native to China, were first found in Virginia in 2004. Since then, there have been 800 reported statewide by fishermen and naturalists, Mr. Odenkirk said.
State officials aren't attempting to extinguish snakeheads, which can grow to about three feet long and weigh more than 15 pounds. Snakehead meat is considered a delicatessen in both China and the United States.
However, it is against state law to keep snakeheads as pets, Mr. Odenkirk said.
The fish got nationwide attention in 2002 after an adult snakehead was caught in a pond at Crofton, Md. Two fishermen threw the fish back after taking photographs, which were shown to state biologists.
Maryland officials, concerned that snakeheads would damage or destroy the ecosystem, poisoned the pond and two nearby ponds.
Two years later, after a snakehead was caught in Pine Lake in Wheaton Regional Park, the five-acre lake was temporarily drained to exterminate the snakeheads.
The region's snakehead population spawned from a Maryland resident, who dumped two adult fish in the pond, according to the Department of Natural Resources.
The resident originally bought the fish on the New York live-fish market, according to the department.
Snakeheads have since been found in Pennsylvania, New York, North Carolina and Wisconsin.
Mr. Odenkirk said snakefish avoid salt waters such as the Rappahannock River, Chesapeake Bay and the Atlantic Ocean. The fish often patrol shores of freshwater rivers and creeks to find food brought in by the tides, he said.