FUTILE FIGHT? Battle against snakeheads in Pine Lake in Wheaton, Md., began in April with temporary removal of native fish before lake drainage (top). But adults later turned up in the Potomac River (bottom). Image: MATT HOUSTON AP Photo
Few invasive species play their threatening parts with as much panache as the northern snakehead. With its toothy mug, scaly head, predatory nature and decidedly unfishlike need to breathe air, this interloper from the waters of eastern Asia made headlines as "Frankenfish" when it was discovered in a Maryland pond in 2002. Worried that a heavy rain could wash the fish into the nearby Little Patuxent River--harming native species in a large, open ecosystem--wildlife officials poisoned the pond, killing a population of some 1,300 northern snakeheads that most likely began with a local resident's release of a few fish. Having launched a public education campaign on the dangers of freeing nonnative species in the wild, officials hoped the snakehead was gone for good.
Two years later they got a troubling answer: the fish, Channa argus, turned up in the waters of the Potomac River, the result of one or perhaps multiple releases along its shores. In May an angler caught a female in a Virginia tributary, and as the summer progressed, the river's tally rose to 19. The biggest blow came September 29, when a juvenile northern snakehead fell out of the aquatic weeds tangled around a boat trailer that was pulled from Virginia's Dogue Creek, another tributary. The result of a midsummer spawn, the juvenile points to a reproducing population in a waterway with tens of thousands of acres of habitat. "This time you can't get rid of them," says Walter Courtenay, Jr., a U.S. Geological Survey research fishery biologist.
This article was originally published with the title Snaking Its Way In.