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Maryland snakeheads take a turn--for the worse

Once upon a time, biologists believed that the deep, cold navigational channel in the Potomac River might keep those voracious aliens, northern snakeheads, on the Virginia side.

Until they appeared in Mattawoman Creek, on Maryland's shore.

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Then biologists believed the salinity of the Chesapeake Bay would keep salt-averse snakeheads bottled up in the Potomac. No less an authority than Walter Courtenay, aka Dr. Snakehead of the U.S. Geological Survey, calmed our fears.

Now it appears the fish that occupies a spot on the federal government invasive species hit list has looped around Point Lookout and has gotten as far north as St. Jerome Creek in St. Mary's County."They're on the move," said Jonathan McKnight, head of the Department of Natural Resources invasive species team. "The hardest part was to get around Point Lookout. Once you're around the point, it's only a bounce to the Patuxent River."

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Don Cosden, the head of DNR's inland fisheries program, said that over the last several years, biologists began seeing snakeheads in Potomac tributaries "farther down than we thought they could go."

They also found them upstream, capturing two snakeheads in the Anacostia River north of the Capital Beltway where DNR stocks trout. One snakehead, said Cosden, had "a really nice rainbow trout in its belly."

Experiments show that while snakeheads can't thrive in water with high salinity levels, "they can and are willing to swim through those areas that are not habitable," Cosden said. "When they find a creek, they make a beeline upstream until they find freshwater."

That apparently explains sightings in the St. Mary's River and Herring Creek, Potomac tributaries.

The appearance in a waterman's net outside the mouth of St. Jerome Creek was a bit of a surprise, however. Luckily, there isn't enough freshwater in the creek to make it a welcoming home. But freshwater can float on top of saltwater to create pathways to new territory.

"They're pretty adapable critters and they have a strong instinct to move when they get some freshwater. If they repeat that behavior enough times, I believe they'll make it to the Patuxent," Cosden said.

McKnight agrees, saying he believes bay waters "will act as a barrier for a time, but I would expect them to continue to move up."

Snakeheads slithered into the headlines in summer 2002, when an angler at a small pond in Crofton reeled in an 18-inch adult. The Department of Natural Resources was forced to poison that pond and another, killing thousands of baby and adult snakeheads, to ensure the fish wouldn't escape into the nearby Patuxent River.

That infestation was caused by a man who bought two fish to make soup, changed his mind and dumped them in the pond.

Later that year, the federal government banned the importing of all snakeheads, natives of Asia. Experts worry that, in time, snakeheads could assert themselves at the top of the aquatic food chain.

The website of the U.S. Geological Survey notes: "Should snakeheads become established in North American ecosystems," it says, "their predatory behavior could drastically disrupt food webs and ecological conditions, thus forever changing native aquatic systems by modifying the array of native species."

Cosden worries that in time snakeheads, which like the same food and habitat as bass, will muscle out the competition. So far, however, surveys haven't shown a dip in the bass population.

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"We don't know how abundant they may become," Cosden said of snakeheads. "I think the population has been increasing. There's only so much room and so much food out there. Something's got to give."

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