The northern snakeheads that have moved into Potomac River may be getting the idea that they aren't wanted. More than 100 fishermen showed up at a Potomac tributary last Friday hungry for a snakehead derby, and not a single fish fell for the trap.

The Marina Operators Association of America and the National Marine Manufacturers Association co-sponsored last week's fishing outing to help rid the tributary of the Potomac of its snakehead infestation, the Washington Times reported. Any fisherman who successfully landed a snakehead would have received a fishing rod, but with every angler going home skunked, the prizes went unclaimed.

The northern snakehead, an invasive species of fish that were illegally imported as food and aquarium pets from Asia, were first discovered in Maryland two years ago. Biologists poisoned the pond that held the fish, killing six adults and about 1,000 immature snakeheads.

This year has brought about a second wave of snakeheads with 16 documented catches since the spring, including that of a 6-year-old specimen, which could suggest that the fish have made a permanent home for themselves in the Potomac. If the snakeheads continue to thrive, fisheries biologists worry about the future of largemouth bass, a popular and economically important game fish. "The snakeheads are voracious predators, and they prey on fish that might utilize the same habitat," Albert J. Spells of the U.S. Fish and Wildlife Service told the Times. "We think large-mouth bass and snakeheads may share the same habitat."

Despite Friday's snakehead drought, the day didn't end without its share of thrills. When Becky Chissler of Poolesville, Maryland, hooked onto something big she hoped it would be a monster fish but it turned out to be an old anchor. Her husband, Bob, didn't see much difference between the rusty metal and an ugly snakehead. "The anchor was her snakehead," he told the Times.