In River of Many Aliens, Snakehead Looms as Threat
Sunday, May 29, 2005
This is the summer of the snakehead, Part II. A year after 20 of the toothy Asian fish were found in the Potomac, the creatures are growing in size, number and legend.
They are far from the river's only invaders. Over time, the Potomac has been so altered by man that it has become the underwater equivalent of the "Star Wars" alien bar. There are carpets of Asian clams and thickets of grass originally from Southeast Asia. Largemouth bass and channel catfish, transplants from other parts of the United States, share the Potomac with carp native to Asia.
Feral goldfish have been spotted -- bigger and browner than usual after being liberated from their fishbowls -- along with the occasional piranha. And scientists estimate that 35 percent of the Potomac's fish species were not there 200 years ago.
So why worry now about a few dozen snakeheads? Because all the previous nonnative species found a niche without throwing the river's ecosystem out of whack. Some scientists said they believe the same might not be true of snakeheads, which are known for their voracious appetites and rapid reproduction.
"It might change the balance, and that's not something you want to happen," said Thomas Orrell, a Smithsonian Institution researcher.
Jim Cummins, a scientist for the Interstate Commission on the Potomac River Basin, compared it to Russian roulette. "We've been lucky in the roulette game of introduced species," he said. "We might be pulling a loaded chamber" with the snakehead.
The northern snakehead, a native of China and Korea that was brought to the United States as food and as aquarium fish, first appeared in the area in 2002. That was when six adults and about 1,000 babies were found in a pond in Crofton. Authorities poisoned the pond to kill those snakeheads.
Last year, however, the fish appeared again -- in the Potomac and some of its tributaries. No one is certain who put the snakeheads in the river, though genetic tests have eliminated any connection to the Crofton fish.
Fifteen more have been caught this year, including one by fisherman Tom Woo that measured more than two feet long. Woo, of Fort Belvoir, said he cast an artificial worm lure at the Mount Vernon Yacht Club's marina, then felt something hit the bait "like a freight train." A torpedo-shaped fish jumped a foot and a half out of the water, he said.
"I was like, 'Whoa, that's a snakehead,' " he said, recognizing the fish because he had caught three.
The other snakeheads caught this year included some as small as 11 inches long. Scientists have said the size differences probably mean that several generations are living in the river. They also said it's a sign that the fish are breeding.
For the Potomac, this is a very old story.