An Invader’s Less-Than-Elegant Move From Water to Land

The much-maligned northern snakehead fish might be less menacing than it was made out to be.

A snakehead fish caught in Maryland in 2002 (Steve Ruark / AP)

When invasive snakehead fish first appeared in the United States, in 2002, the secretary of interior herself called a press conference to warn of impending danger. “These fish are like something from a bad horror movie,” she told reporters. “They can eat virtually any small animal in their path. They can travel across land and live out of water for at least three days. They reproduce quickly.” What’s more, they can breathe air, and they have razor-sharp teeth. The interior department banned the importation of snakeheads to the U.S.

Meanwhile, National Geographic dubbed the snakeheads “fishzilla.” They inspired actual bad horror movies, with titles such as Frankenfish and Snakehead Terror. And as snakehead fish have continued to spread to new parts of the U.S., most recently Georgia, the advice has been blunt and unsparing: “Kill it immediately.”

But after almost two decades in the U.S, the horror of the snakehead fish has not come to pass. They’ve had little ecological impact on most of their new habitats. They definitely haven’t chased any humans around on land. (Hello, Frankenfish.) In fact, after all that hype, it’s not even clear how well the species in the U.S., the northern snakehead fish, can travel across land—if at all.

Noah Bressman

That’s how Noah Bressman, a graduate student at Wake Forest University, ended up spending the summer of 2018 catching northern snakeheads and trying to coax them out of the water. He was surprised, he told me, to find nothing in the scientific literature about how northern snakeheads move on land. The Interior Department’s ominous 2002 press conference had lumped together all snakeheads, which comprise a whole family of fish species found in Asia and Africa. Some were known to move on land. Others, such as the northern snakehead fish, were less studied.

With the help of the Maryland Department of Natural Resources, Bressman ended up catching several hundred northern snakehead fish. He then subjected them to a battery of poor water conditions, including low oxygen, low pH, high pH, salt water, hydrogen sulfide, and crowding. The low-oxygen water didn’t seem to affect the snakehead, which makes sense because they have evolved to breathe air. But when the water was too acidic or too salty or too high in carbon dioxide, a number of northern snakehead fish climbed out of the water via a wooden ramp.

Bressman also separately videotaped snakehead fish moving on land. Not of all them really moved, and the ones that did look quite clumsy. They kind of bend their body back and forth in a sinuous, serpentine motion—but with none of the grace or efficiency of actual snakes. The fastest they went was about half a foot per second. Bressman said he saw fish that moved a total of 20 feet back and forth.

Altogether, his study lays out a case that snakeheads can emerge from water when conditions are poor—to find better places to live. “I think this is really rare behavior to see in the wild,” he said. “But in terms of a management perspective, even a rare behavior can still have big impacts.” In other words, this behavior might be helping snakeheads spread across the U.S.

But will snakehead fish actually do this in the wild—outside of artificial lab conditions? Not everyone who manages fisheries with snakeheads is convinced. John Odenkirk, a biologist with the Virginia Department of Game and Inland Fisheries, says he’s seen no evidence of significant overland movement. In any case, he has clearly been irritated by all the hype about snakeheads over the years. “There’s still this ingrained fear in a lot of people that snakeheads are these evil fish that are extremely destructive,” he says. “We’ve been working for 20 years to calm people down.”

In Arkansas, Jimmy Barnett, the aquatic-nuisance-species coordinator with the state’s Game and Fish Commission, says, snakeheads are often found in rice paddies there. When rice farmers drain the paddies, the fish seem capable of wriggling around in the mud until they find a ditch with water. However, he says, “they’re not going to get up and walk across dry ground from one area to another.” According to Joshua Newhard, a fish biologist with the U.S. Fish and Wildlife Service in Maryland, snakeheads that find themselves struggling in large waterbodies will probably just swim to another part of the river or reservoir in search of better conditions. “Perhaps, in a very small waterbody (i.e. a pond) with poor conditions snakeheads may opt to get out via land if possible,” he wrote in an email. But those cases would indeed be rare.

Ultimately, snakeheads are more likely to spread through another means: humans. “It’s mostly humans moving things around that allow these things to occupy new environments,” says Emily Standen, a biologist at the University of Ottawa who has studied other air-breathing fish. Bressman and his co-authors acknowledge the same role of humans in snakehead spread, as well. And that gets at how snakehead fish made it to America in the first place.

Northern snakeheads, it turns out, are delicious. In their native Asia, they are prized for their mild, white flesh. Before they were banned in the U.S. in 2002, snakeheads were sold at pet stores and live-fish markets. They specifically ended up in Arkansas because a farmer there was growing them to sell commercially, and they escaped into the wild when he shut down his operation following the ban.

Since then, though, word of their deliciousness has spread to high-end chefs and foodies willing to pay $22 a pound. Last year, at the first International Snakehead Symposium, which Odenkirk co-organized and where Bressman presented some of his initial research, scientists discussed the impact of the invasive species—while snacking on snakehead ceviche, snakehead egg rolls, and snakehead and grits. “I highly recommend,” Bressman said.