Invasion of the Snakeheads

The voracious "Frankenfish" has turned up in the Potomac River, Lake Michigan and a California lake, sparking fears of an ecological Armageddon

Smithsonian Magazine | Subscribe

(Continued from page 2)

Electrofishing, a common sampling method in fisheries research, isn’t meant to kill fish. But it may knock them out for a while. (It’s not considered sporting and requires a special permit.) Odenkirk nosed the boat in and out of the empty slips at the Mount Vernon Yacht Club a couple of miles downriver from Little Hunting Creek. Tiny fish leapt out of the water as others lolled gracelessly on their backs, stunned, just below the surface. Biologist Steve Owens and technician Scott Herrmann leaned over the bow clutching long-handled nets. Afish’s response to the electrical current depends on its skeletal structure, scales, size and how close it is to the wires. “Snakeheads are—they’re kind of bad-asses,” Odenkirk said. “They don’t like the juice and they try to avoid it.” Still, a snakehead that got close to the trailing wires would be stunned and surface, for Herrmann or Owens to snag. At least, that was the theory. We sped back up the Potomac past Mount Vernon to Little Hunting Creek, where the first Potomac snakehead was caught by a fisherman back in May. At the end of an hour and a half of electrofishing, the catch included many carp, several species of catfish, a bunch of goldfish, a long-nosed gar, a turtle— and zero snakeheads. Odenkirk said he’s always conflicted after an unsuccessful day of snakehead fishing. On the one hand, he said, he was disappointed he’d failed to catch one. On the other, “you’d be happy if you never saw one again.”

Though we didn’t see any snakeheads that day, Odenkirk says he’s sure the fish is established in the Potomac or soon will be. “It’s just not even an option that we’ve caught them all.” He says the fish probably nest in wide, shallow expanses of lily pads and wetlands. “We just can’t get back in those areas.”

But other officials say they’re not convinced the fish are here to stay. Steve Early, assistant director in the fisheries service at the DNR, worked on the Crofton pond in 2002 and has handled some of the Potomac snakeheads. He thinks the fish were only very recently dumped in the river, perhaps after Virginia’s 2002 ban on snakehead ownership. He points out that most of the snakeheads caught this year have been 2 to 6 years old, and that if they’d been living in the Potomac for years, surely someone would have caught one before. Early remained unpersuaded even after a baby snakehead was found in a Potomac tributary this past September. It was the 20th northern snakehead caught in the Potomac watershed, and the first juvenile. “Well, it’s not good news,” he says of the discovery, but points out that if some snakeheads do manage to reproduce, they may never thrive in the big river. Their future also depends on whether other fish in the Potomac develop a taste for snakehead fry.

For now, scientists are working on figuring out how the adults got there. It’s a critical question—if the fish were just recently dumped in the river, there’s a chance they’ll die without having generated a self-sustaining population—but it will require more than a rod and reel or a stun gun to answer.

Behind a door at the National Museum of Natural History in Washington, D.C. rest specimens from the world’s largest fish collection. Smithsonian ichthyologist Thomas Orrell walked down an aisle between rows of gray metal shelves containing jars with labels such as “China 1924.” Orrell held up a jar marked Channa argus, the northern snakehead. “They’re really beautiful fish,” he said.

Orrell is trying to learn if the northern snakeheads caught this past summer in the Potomac were born there. He’s analyzing DNA from 16 fish; if some of the Potomac specimens are closely related, it’s likely that the fish bred in the river. If they’re not kin, they were likely dumped in the river. Orrell is also comparing the DNA of Potomac fish with that of those caught in the Crofton pond, testing the idea that someone might have captured juveniles before the pond was poisoned and released them in the Potomac.

Orrell led me down a bare stairwell into the museum’s basement, past sandbags piled near an entrance in case of heavy rain and a walk-in freezer that smelled of long-dead fish, containing, among other things, an enormous tuna frozen since the 1960s. He lifted the top of a nearby freezer chest, rooted around and pulled out a long, black lump. “Watch out for flying debris,” he said, unwrapping a black garbage bag and scattering pieces of frozen blood. Inside was one of the most recent Potomac catches: a dark, diamond-patterned snakehead more than a foot long, now solid as a rock. After showing it off, Orrell shrugged, wrapped it up, laid it back in the freezer and washed his hands. He already knows whether the snakeheads are reproducing in the Potomac, but he isn’t telling; adhering to scientific protocol, Orrell declines to share his data until they’ve been reviewed by other experts and published in a scientific journal.

If northern snakeheads do have some ecological impact in the Potomac, largemouth bass are likely to suffer, says U.S. Geological Survey fishery biologist Walter Courtenay, who in 2002 wrote a snakehead risk assessment for the agency. The two species have similar habitats and would probably eat each other’s young. Capt. Steve Chaconas, one of only a few full-time fishing guides on the Potomac, does not like snakeheads one bit. “Of course, I’m worried about what potential it could have to impact the fishery,” he says. “Also because I’m a businessperson and my business relies entirely on people coming here to fish.” Even now, he says, customers ask how much the snakeheads have hurt fishing. It’s hard to estimate the extent of the snakehead’s impact on largemouth bass and other Potomac species. The northern snakehead was introduced to rivers in Japan in the early 20th century, but there has been little study of its ecological effects there. (The largemouth bass, native to North America, was introduced to Japanese waters in 1925 and is reportedly terrorizing native fish and snakeheads alike.)


Comment on this Story

comments powered by Disqus