Voracious invader: Nonnative snakehead wreaks havoc

Imagine a fresh water fish that can grow to the size of a rolled-up tent, has an appetite so voracious that it feeds on small mammals, and has reportedly killed humans with its razor-sharp teeth. Now imagine that this fish, after clearing a lake of all food sources, can emerge on the shore and squirm across land for days on its dorsal fins to find a new loch filled with fresh prey.

Northern snakehead caught in a lake in Maryland in 2002. Officials suspect the Asian import got too large to be kept as a pet and was released. photo by Maryland Department of Natural Resources

In the last four years, such a creature has been an unwelcome invader in many American waters. The so-called snakehead fish, however, has not squirmed its way across the country on its own. Instead the fish has traveled in cargo ships and along interstate highways. Importers have smuggled the live fish into the country for sale in Asian food markets where consumers are eager for a taste of home or in pet stores for sale to hobbyists. Occasionally, imported snakeheads end up in a lake or stream instead of on a plate.

Named for its less-than-photogenic appearance, the snakehead is actually many species within the family Channidae. With its unique ability to breath air through its suprabronchial chambers, the snakehead may be the most colorful of the hundreds of invasive species in the U.S. Invasive species represent a tremendous cost to the environment, and ecologist David Pimentel of Cornell University has estimated that they cost the U.S. $100 billion annually. They also impact almost one half of native species that are listed as endangered.

In Asia, instead of conjuring images of Godzilla the snakehead brings to mind tasty filets and fish stews with perceived medicinal properties. In fact, the snakehead is a delicacy in much of that region. (There cultivators of snakeheads must wear helmets and protective gear to avoid injury and enclose growing ponds with cages in order to prevent escape.) Recently, live snakeheads sold for $15 per pound in Los Angeles.

In order to combat the spread of this invasive species, law enforcement officials are springing to action. On May 14, federal officials arrested Koreatown grocer Sung Chul Rhee after investigations revealed several snakehead shipments to his market disguised as sea bass shipments. Assistant U.S. Attorney. Joseph O. Johns said that the prosecution is not intended to 'indict any one cultural practice' but hopes that it 'informs those cultures that might be doing the importation of these injurious species.'

No one is quite sure what effect the introduction of the snakehead will have on the ecosystems it inhabits, but most ecologists expect the worst. To date, five species of the snakehead have been found in U.S. waters. When officials find a snakehead they rush to the site and take immediate action. Typically, an entire lake will be poisoned and then restocked with native species.

The first known introduction of snakeheads in the continental U.S. occurred in 1997 in Silverwood Lake in California. But the snakehead found fame and fortune when it turned up in Maryland and New England. In October 2001, the Massachusetts Fish and Wildlife department located a northern snakehead in Newton Pond in Worcester County. In Boston, an angler in the Charles River caught two blotched snakeheads. Officials also linked all of these fish to local ethnic markets. In May 2002, a northern snakehead was caught in a Crofton, Md., pond. Over 100 juveniles were caught, and officials poisoned the lake.

The discoveries of snakeheads in the northeast spawned a media frenzy. David Letterman featured the snakehead in one of his top-ten lists and The New Yorker magazine even covered a snakehead vs. crab race on land. Who won? The snakehead.

So how do fish that are imported for fish markets end up in lakes and streams? At least one study has postulated that sellers and/or consumers of the fish hope to create a live supply of snakehead fish close to home. Others believe some fish collectors find the snakeheads too voracious for their home aquariums and set the fish free.

Wildlife officials in Florida have expressed resignation and acceptance of the strange invader. They have little choice: The bull's-eye snakehead has become a permanent resident in South Florida since officials cannot poison the entire network of lakes and canals in the area. Since this particular species of snakehead cannot survive winters north of South Florida, the fish is not likely to waddle up I-95 anytime soon. And already 32 species of fresh water invaders live in South Florida, so the snakehead is just one of many insults to the native environment. Encouragingly, so far it has not yet decimated all in its path.

In Virginia, however, officials are more sanguine about the effects of the snakehead. In the last three months, nine specimens have been fished out of the Potomac River. Unfortunately, as in South Florida, once the fish has infested open waters, nothing can be done. William Woodfin, director of the Virginia Department of Game and Inland Fisheries, commented that no one knows how the snakehead will impact the river and its tributaries, but its effect 'will be noticeable and significant.'