The northern snakehead, native to China, Korea and Russia and resembling a cross between an eel, a snake and a piranha, has been found in wide areas of the Potomac basin, the (Norfolk) Virginian-Pilot reported Tuesday.
"We're talking about 100 miles of waterway, in all these creeks and canals," John Odenkirk, a biologist with the Virginia Department of Game and Inland Fisheries, said. "There's just no way you could eradicate all of them."
Snakeheads have been found in almost every creek and tributary from Washington, D.C., south to the Chesapeake Bay.
Snakeheads are a popular, relatively cheap food fish in Southeast Asia, and because they can breathe oxygen and live out of water, they are believed by some to have medicinal benefits.
Scientists say they do not appear to be taking over the ecosystem, as some officials feared six years ago when the first population of wild, reproducing Asian carp was confirmed in the Potomac.
So far they have not damaged the Potomac's prized largemouth bass population, or that of any other fish, bird or amphibian on which they feed.
"We haven't seen any of the really bad, negative ecological effects," Steve Minkkinen of the U.S. Fish and Wildlife Service said.