Snakeheads Appear at Home in the Potomac

It was a nest, but there was no doughnut hole.

"The fish aren't behaving here the way they might be expected to behave in Asia," said John Odenkirk, a snakehead expert and a biologist with the Virginia Department of Game and Inland Fisheries.

Researchers are similarly confused about whether the river's snakeheads migrate. One Sunday last fall, Dogue Creek was suddenly full of hundreds of fish heading upstream, so thick that fishermen snatched out at least 80. This may have been a freak event caused by a large rainfall -- or it may have been the first running of an annual ritual. Researchers are keeping watch to see what happens this year.

What little scientists do know about the snakehead's habits was gathered this spring, when Odenkirk inserted small tracking devices into the body cavities of 20 fish. He found them to be mainly homebodies, lurking in the same weedy and shallow spots week after week.

But some strayed farther afield: Fish No. 1204 crossed the deep midsection of the Potomac to visit Maryland's Piscataway Creek. Fish 1301 disappeared completely, meaning that it was perhaps speared by a heron, caught by an angler or just moved so far away that Odenkirk can't get the signal.

"It tells me that some obviously are bucking the trend and being a little more adventurous and crossing the main-stem Potomac," Odenkirk said.

This year's catch of snakeheads has made it clear how widespread the fish have become. In Maryland, the fish have been found across an unprecedented swath of creeks in Prince George's and Charles counties.

On the Virginia side, snakeheads have moved north from their epicenter to a creek near Belle Haven Marina in the Alexandria section of Fairfax. To the south, Odenkirk said, their numbers have increased substantially in the Occoquan River basin, on the border between Prince William and Fairfax counties.

They've also appeared in another place puzzlingly far afield: Kenilworth Park and Aquatic Gardens in the District. In the late spring, more than 500 baby snakeheads and a handful of larger adults were found in ponds there, having eaten almost every other fish in the water.

D.C. officials think that this may be a separate population of snakeheads, descended from fish dumped directly in the aquatic gardens.

But because the ponds share connections with the Anacostia River, there's some chance the D.C. snakeheads might be adventurous specimens from the Potomac.

For all that's known about the snakeheads' expanding reach, much more is still in question. That was obvious Wednesday, when Odenkirk and two assistants set out on the Occoquan in a shallow boat with a spindly metal claw dangling from its front. They were electro-fishing.