Dedicated to the Conservation of Southeastern Fishes
Snakehead's Latest Lair May Be The Potomac River
June 10, 2004
OCCOQUAN - So fierce a predator is the snakehead fish - and so menacing to the ecosystem - that the mere sighting of the creatures compelled Maryland officials to drain one pond and poison another.
Now there's a bigger problem.
Five have been caught in the Potomac River this spring.
"We can't drain the Potomac," said John Odenkirk, a marine biologist with the Virginia Department of Game and Inland Fisheries, who is working with U.S. and Maryland officials to figure out how to eliminate the alien species.
Most days, they've been out on boats unsuccessfully hunting the elusive eater in shallow reeds and lily pads. They've posted signs at marinas with a picture of the saw-toothed swimmer and a warning to fishermen: "If you find a snakehead fish, kill it."
The dead fish are being turned over to the Smithsonian Institution, which is testing their DNA to learn whether any breeding has taken place in the Potomac.
"'I don't know,' that's m y answer to everything about the snakehead," Odenkirk said last week, steering a motorboat into to Occoquan Bay, off the Potomac in southern Fairfax County. "We're trying to learn as much as we can. The worst-case scenario is that species could exponentially increase and replace all of our desirable species, like the largemouth bass."
There are about three dozen different types of snakehead fish, most of them native to Asia. The northern snakehead, the species turning up in the in the Potomac, is indigenous to China, Korea and Russia, where they are regarded as a delicacy and a remedy.
They were shipped live to the United States as food and exotic pets until 2003, when Congress banned their importation. The General Assembly passed a law that year making them illegal to possess in Virginia.
Scientists suspect the fast-growing fish were tossed in the Potomac by owners who tired of feeding them. A northern snakehead grows up to 33 inches long and can easily eat three dozen goldfish a week .
In the wild, it feeds on fish, frogs and any other aquatic life it can push through its jaws with its sharp, inward-slanting teeth.
Snakeheads are generally tan with dark brown mottling. They have long bodies that are often mistaken for bowfin, sea lamprey and eels. A key difference is that snakeheads have a long dorsal fin.
They have an amazing ability to survive in water or on land. Snakeheads can breathe air through a primitive lung that allows them to live out of the water for up to three days. Although there have been some reports that the creatures can move impressive distances on land, Odenkirk said that ability has been "greatly exaggerated."
They hunt in shallow reeds and lilies.
They hibernate in cracks and crevices during the winter and go dormant in the mud during droughts.
Snakeheads have no natural predators in the Potomac River. "The concern is that we could end up with a whole system of snakeheads and not much else," Odenkirk said.
The first alarm sounded two years ago when the fish was found in a murky pond in Crofton, Md. Game officials poured enough poison into the pond to kill every fish in it, including hundreds of juvenile snakeheads and six adults.
They were owned by a resident who bought them in New York to make soup for a sick relative. When the relative recovered, the unused fish were dumped into the pond, where they reproduced quickly.
In April, a snakehead was caught in a pond at a regional park in Montgomery County, Md., a few miles northeast of the Potomac.
Maryland officials drained the pond and found another snakehead.
Since May, however, five have been caught in the Potomac. Three were snagged by recreational fishermen, one by a professional fisherman and one by an official of the Maryland Department of Natural Resources.
Virginia marine biologists have yet to catch one, but not for lack of trying.
Odenkirk and his colleagues have logged scores of hours electro-fishing in the shallows of the Potomac. Through an antenna-like prod hanging over the bow of their motorboat, they release a 6-amp current into the water. It's enough to stun the fish and send them to the surface.
Odenkirk steered the boat during a recent excursion while two colleagues stood with nets, capturing, classifying and releasing the dazed fish. Each species reacted to the shock differently. The yellow carp lay motionless on their sides.
The catfish shuddered spasmodically, whiskers twitching. A white perch swam in circles, as if part of their fins had been paralyzed. After a minute or two, the fish moved normally.
Osprey, blue heron and bald eagles soared overhead. Turtles basked on logs. Snakes curved by, their heads barely above the water.
In four hours, Odenkirk and his colleagues netted more than 300 fish of 21 different species. They let hundreds more float by.
Nowhere was a snakehead to be found. That was mixed news.
Odenkirk and his co-workers were a little disappointed. After weeks of searching, they were hoping to catch a snakehead, especially after Maryland game officials snared one. Once, when Odenkirk's cell phone rang, he quipped, "It's Maryland. They've shocked six snakeheads today."
It was a good day for the Potomac River, however.
"It appears that the snakehead may not be as plentiful as we thought," Odenkirk said. "If we can't find them, the chances of sexually mature males and females finding each other may also be slim." The search will go on, although biologists will discontinue their use of electric shocks and focus on looking for potential nesting areas.
Odenkirk put his hands behind his head. "When you combine all these fish we've seen today with the birds and snakes and turtles, it means that we still have a healthy system."