Snakeheads Appear at Home in the Potomac
Monday, October 2, 2006
The northern snakehead fish seems to be expanding its territory in the Potomac River, government researchers say, after a year in which the toothy Asian transplant has appeared in new places and at higher concentrations across the area.
In the third year that the fish has been studied in the Potomac, scientists are starting to build a portrait of the snakehead at home in the area. Some of the most frightening concerns have been dispelled: The fish turn out to be well-nigh helpless on land (early reports said the snakehead could wriggle short distances out of water), and the creatures haven't gobbled up or driven out the Potomac's famous bass.
But worries remain, because the snakeheads are reproducing rapidly and starting to push outward. The next few weeks will bring a crucial test of the snakeheads' growth, and science's understanding of them, as researchers wait to see if last October's startling mass snakehead migration is repeated.
"It looks like they're becoming pretty solidly entrenched, as far as establishing that beachhead here in the Potomac," said Steve Minkkinen of the U.S. Fish and Wildlife Service.
Over the past year, the snakeheads have spread out and become endemic in about 15 miles of the Potomac and some of its tributaries south of Washington from a home base of two creeks in Virginia, he said.
That has switched scientists' focus from eradication to coexistence. "As much as we can, we're just trying to collect information," Minkkinen said.
The story of snakeheads in the Potomac may have begun as early as 1998 or perhaps as late as 2002. The key event, scientists believe, was when a male and female were dumped into the water and found each other in Fairfax County's Dogue Creek. Since then, that stream, along with nearby Little Hunting Creek, has become the epicenter of the Potomac's snakehead population, scientists say.
Now, the two creeks are also the area's premier snakehead laboratory, as researchers seek to understand the life the fish have created in an alien home.
One obvious conclusion: Snakeheads are thriving. Virginia state scientists who use electric current to stun and capture fish in these creeks used to catch one snakehead every five hours. This year, they got 6.9 fish an hour, nearly 35 times more.
But the snakeheads don't appear to have had a serious impact on the river's largemouth or smallmouth bass, which are also top predators in the river. Scientists say they believe this might be because the snakeheads prefer shallower water or different prey.
"A bass is probably more likely to eat one of them" than a snakehead eat a bass, said longtime guide Ken Penrod, who said he hadn't seen any change in the bass fishing. "It's a lot about nothing, I think."
But scientists say they still have a lot to learn. They're unsure how the snakeheads nest, for instance. In their native habitat, they are said to clear out a "doughnut hole" in a thicket of underwater vegetation and lay their eggs there. But this year, a Virginia biologist spotted a cloud of 500-plus snakehead babies -- orange and black, with a minuscule version of the distinctive snakehead mouth -- swirling in Little Hunting Creek.