Potomac Fever

That name came from the snakehead's first appearance in an Anne Arundel County pond. Around 2000, a man who lived in Crofton had ordered two live snakeheads from an Asian fish market in New York, wanting to make his sister, who was ill, a pot of snakehead soup. But the sister got better before the fish hit the pot. The snakeheads, a male and a female, were set free in the pond. They made babies.

In 2002, an angler caught one of the fish, setting off a panic. Scientists reported that the snakeheads could crawl across land, breathe air and eat anything. "It's the baddest bunny in the bush," one Maryland biologist said.

The state tried fish traps and electro-shocking to get rid of them, before finally going to the "nuclear option." The pond was filled with milky poison, killing the snakeheads and everything else. The final body count showed that in two years, two snakeheads had become more than 800.

The hubbub inspired two straight-to-cable movies, both of which featured enormous snakeheads chowing down on people. But in real life, scientists exhaled after Crofton: The threat seemed to be over.

Then the bad bunnies started turning up in the Potomac. In early May 2004, a 12.5-inch fish was caught in Little Hunting Creek, a tributary near Mount Vernon. Several days later, a foot-long fish was caught in the Potomac near the Charles County shore. A few days later, a third was hooked near Occoquan.

Now, three years later, the range of the Potomac snakeheads starts in Northeast Washington, at the Kenilworth Aquatic Gardens on the Anacostia River, and extends about 45 miles downriver to Aquia Creek, in Stafford County. In between, scientists say, there could be hundreds or even thousands of snakeheads, though some of Frankenfish's original hype has turned out to be overblown. They can't, for instance, waddle any significant distance on land. They haven't eaten every other fish in the river. But they are odd, adaptable beasts: Snakeheads can breathe air and can survive for hours or even days out of water. They have gnarly rows of sharp teeth in their mouth, and even in their throat -- not for chewing prey, apparently, but to make sure the things they vacuum down can't wriggle their way out again.

There are 29 species of snakeheads spread from Iran to Siberia, with the biggest concentration in Southeast Asia. A lot of people farm them for food -- the northern snakehead is grown in ponds in China, then sold alive to fish markets -- and a few people, mainly Western or Japanese tourists, catch them for fun.

Researchers still aren't sure how northern snakeheads wound up in the Potomac. Most people guess that two or more were dumped out of aquariums somewhere near Mount Vernon. Then those few became many, and they started their colonization in a pair of tributaries on either side of George Washington's estate. They have thrived: Unlike other snakehead species, this one can live through an icy winter.

"Now they're over 75 kilometers of river. That's pretty successful," for just a few years' breeding, says Steve Minkkinen of the U.S. Fish and Wildlife Service. Already the snakeheads are getting very, very big. In May, Minkkinen was out electrofishing in Dogue Creek and saw a monster that escaped his net. He estimated the fish weighed 20 pounds. (The International Game Fish Association's record for northern snakeheads, set by a fish hooked in Japan in 2004, is 17 pounds, 6 ounces.)

Some scientists and bass fishermen fear that, in the coming years, the snakeheads' expansion will come at the expense of largemouth bass (both are nonnative, of course, but the bass's longer tenure in the river and its value as a sport fish have put the state on their side). The newcomers might eat the bass's young, they say, or -- because the two species prefer similar spots in which to hunt and spawn -- the larger snakeheads might simply crowd the bass out. Some anglers think they're already seeing a decline in the bass fishery in such snakehead hot spots as Dogue Creek. And some scientists worry that, if snakehead fishing takes off in the Potomac, somebody might purposely dump the fish into another body of water, and start the cycle over again.

To prevent snakehead mayhem, D.C. area officials organized a "roundup" in 2004, recruiting some of the river's leading fishermen to go after the invaders. There was Cliff Magnus, a woodworking artist from Waldorf, who had already caught a six-pound snakehead. There was Tom Woo, a stay-at-home dad from Fort Belvoir, who had once caught three snakeheads in 10 days. And there was Chaconas, who was then so worried about the snakeheads' impact on bass that he helped persuade extra fishermen to participate.

The anglers roared off from a marina near the Pentagon with what sounded like an easy mission: Catch as many of the it'll-eat-anything fish as possible. When the boats returned later that day, they had hauled in a lot of bass and other fish. But not a single snakehead.