Invasion of the Snakehead Fish

by Thomas Twain

Since their discovery in a Crofton pond late in June of 2002, the northern snakehead fish, humorously dubbed “Frankefish,” has become a serious and heavily debated topic. The northern snakehead fish is a vicious, unrelenting predator that has no natural predators in the Potomac tributary region that it has spread to. The uncanny thing about the snakehead fish, however, is its ability to wiggle, or “walk,” across dry land while breathing air with its primitive lung. Experts agree that the snakehead fish can survive out of water for two to three days as long as they are in a moist environment. Scientists are in hot pursuit of the snakehead fish because of concerns that, in a predation-free environment, the snakehead will quickly establish itself at the head of the food-chain and possibly radically change the ecosystem by eating or displacing the other fish. Snakehead fish, with sharp teeth and powerful jaws strong enough to bite other fish in half, require large amounts of food and feed on anything from frogs, aquatic birds, and small mammals so that they aren’t continuously hungry. The torpedo-shaped, toothy meat-eaters are native to China and can be found in other parts of Eurasia. In Singapore, the snakehead is considered a savory delicacy served with apples and ginger and it is also a vital ingredient used in soups and as a curative.

The northern snakefish, with its torpedo shaped body, long dorsal and anal fins without spines, and toothed jaws, does bear a resemblance to and may be confused as the native bowfin (mudfish), sea lamprey, American eel, . It may grow to about three feet long and its jaws contain numerous canine-like teeth (similar to a pike or pickerel). Typically found in stagnant shallow ponds, swamps, and slow, muddy streams with vegetation. The snakehead typically has red eyes and is gold-tinted brown to pale grey in younger fish, while the older fish are dark colored and have large black splotches. There is often a distinctive marking near the base of the tail fin that is a black spot rimmed with orange, known as an eye-spot or ocellus.

Shortly after the snakehead fish discovery in Crofton, the Deparment of Natural Resources formed a Snakehead Scientific Advisory Panel to address the issue. A few weeks later, the Crofton pond was poisoned and the fish were exterminated. In April more snakehead fish were found in Wheaton Regional Park’s Pine Lake and that lake had to be drained in order to make sure the snakehead fish were eliminated. Since April, there have been at least six confirmed captures of snakehead, all within an eight mile stretch of the Potomac, with the most recent being on June 17th. It is important to note that the most recent catch was of a sexually mature specimen which means that reproduction amongst the snakeheads may have been occurring for some time.

Although scientists are concerned now about how the snakehead fish have been distributed, it could take years before the effect on the ecosystem is observed or understood. Wildlife researchers are currently awaiting test results to determine if there is any relation between the snakeheads found in the Potomac River and those found in Crofton. Florida officials say that concerns about snakeheads may be overblown. A similar species discovered in a Broward County canal system four years ago has had little effect on the large-mouth bass, sunfish and blue gill populations, they say. There are very few examples of how the non-native snakehead interacts with native species and many are skeptical that there is anything to worry about. Biologist are not taking any chances, however, and have been “electro-fishing” several times a week over a 10-mile stretch in order to find any young or recently hatched snakehead fish that may be lingering near a nesting site. One encouraging sign is the fact that no females capable of spawning have been found. When the snakehead fish does spawn, they lay about 15000 eggs and can spawn up to five times a year. This may be a serious issue because the snakehead fish is able to survive where many other fish can’t, allowing them to continue to repopulate, and potentially transmit and spread parasites or diseases that could effect humans.

There have been reports from China of the giant snakehead fish, a distant cousin of the northern snakehead, attacking and wounding people, but all of those incidents involved the snakehead protecting their brood of young. The nests are typically located in dense vegetation near the waters’ surface. Locally, there has been only one unsubstantiated report from Newport News Daily press which reported that a fisherman had suffered a suspicious bite in the salty waters around Virginia Beach, where the Chesapeake Bay meets the Atlantic Ocean. The problem with this report however, is that the northern snakehead is native to freshwater rivers and streams in Asia and does not tolerate salinity well. Additional research from Japan also shows instances where largemouth bass were shown to prey upon the snakehead population enough to cause a significant decline. Reports from China also show that it could take up to 14 years for a snakehead population to double, but only in ideal conditions. Snakeheads have been found in Wisconsin, California, Texas, Massachusettes, and Florida, where there is a spawning population. As a result the United States Fish and Wildlife Service made it illegal to import live snakehead into the US and to transport live snakehead fish across state lines.

Anglers are asked NOT TO RELEASE a suspect fish, but to kill it humanely with a blow to the head and to get it on ice as quickly as possible. Anglers should report their catches to authorities immediately:

Virginia — Call the Virginia Department of Game and Inland Fisheries in state, toll-free at 1-800-770-4951. Out-of-state callers reporting snakehead fish caught in Virginia waters should call directly to 804-367-1258.

Maryland — Call the Maryland Department of Natural Resources at 410-260-8320, or toll-free at 1-877-520-8DNR, ext. 8230.