Invasion of the Snakeheads- page 4 | Science | Smithsonian

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

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In southern Florida, a close relative of the northern snakehead, the bullseye or cobra snakehead, has been living for a few years in the canals of BrowardCounty. The fish, which is native to rivers in South Asia and Southeast Asia, can grow to four feet or longer, but there are not yet enough data to know what effect the bullseye snakehead has had or will have on Florida ecology. Courtenay says the fish probably first got into Florida waters through ritual animal release, a common practice in East Asia that some immigrants have continued in their new land. (A study conducted in Taiwan in the 1990s, for instance, found that 30 percent of Taipei citizens— most of them Buddhists—had released animals as part of a prayer.)

Florida is home to dozens of introduced fish. Paul Shafland, a fisheries scientist with the Florida Fish and Wildlife Conservation Commission, has worked with invasive fish for 30 years, but he isn’t as troubled by them as most biologists. “We have philosophically, largely determined that exotics are inherently bad, and that’s fine,” he says. But, he adds, some introduced fish might fill up some part of the food web that was previously unoccupied.

In fact, introduced fish are just about everywhere. Rainbow trout, native to the western United States, have been transplanted into cold waters all over the Midwest and East. In the Great Smoky MountainsNational Park, on the border between Tennessee and North Carolina, rainbows have taken over at least 70 percent of the native brook trout’s territory since the 1930s. In the late 1960s, the walking catfish, an Asian species that really can move over land, escaped into the Florida wild. They’ve walked their way into warm waters throughout the southern half of the state, without causing major damage so far, Shafland says.

Lake Michigan, says Philip Willink, an ichthyologist at Chicago’s FieldMuseum, is also infested with nonnative fish. “Out of eight species of salmon here, six are introduced,” Willink says. But, as in the Potomac, some native fish still hang on in the lake, and he says it’s worth fighting new invasions. “We’re just trying to preserve what is left, because once it’s gone, it’s gone.” Since the Lake Michigan snakehead was found in a fairly deep harbor with little vegetation—an unlikely snakehead habitat—Willink surmises that the fish was probably just tossed into the water. Scientists did some electrofishing in the harbor to look for more snakeheads but didn’t turn up any.

The Potomac is not the river it was when George Washington looked upon it from Mount Vernon and made good money selling native shad. Goldfish, carp, channel catfish—none is native to the river. The now-widespread common carp, brought over from Europe, was put in the river in the late 1800s. Carp stir up a riverbed and make the water too cloudy for some other fish. The largemouth bass, native to other U.S. rivers, was introduced into the Potomac in the 1800s. And the blue catfish, a sharp-spined transplant from the Mississippi River basin that arrived in the Potomac late in the 20th century, is a headache for fishery managers now, who fear it could interfere with the commercial fishing of channel catfish—which were introduced from the Mississippi basin decades earlier. Descendants of released pet goldfish flourish in the Potomac, as they do virtually all over the world. But the other introduced species aren’t the point; the native fish are, says Dan Simberloff, an ecologist at the University of Tennessee, Knoxville. If the snakehead is different enough from the predators that natives have evolved with, it might drive some natives to extinction. It’s hard to predict what will happen, though. “Most invasive species don’t cause a huge amount of trouble, but some fraction of them do, and we haven’t been too good at predicting that,” he says. About the snakehead, he says, “I’m not optimistic.”

Cliff Magnus is a semiprofessional fisherman (he says he’s been sponsored for the past ten years by “Team Spouse,” a.k.a. his wife, a lawyer), but the attention he got from catching a snakehead last June in a Potomac tributary has brought him sponsors willing to pay his entry fees for bass tournaments. Magnus may have witnessed a seminal moment. He says he saw two northern snakeheads swimming around each other in Little Hunting Creek in late July. The fish were chasing and nipping at each other. The scene, which he described to some fisheries biologists, wasn’t exactly the makings of a Snakehead Terror sequel, but it was definitely ominous. The way the biologists see it, the fish were getting ready to spawn.

 


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