( Channa argus )
DESCRIPTION: The northern snakehead has a long, thin body that can grow to 47 inches and 15 pounds. It has a somewhat flattened head with eyes located in a dorsolateral position on the anterior part of the head; tubular anterior nostrils; elongated dorsal and anal fins; and a truncated tail. As the name implies, the scaled head of the fish looks like a snake and includes a large mouth with sharp teeth and protruding lower jaws. Snakehead change color as they mature; younger fish may be gold-tinted brown to pale gray in color, while older fish are generally dark brown with large black blotches. Northern snakeheads look similar to the native burbot and bowfin. The burbot can be distinguished from the northern snakehead by a split dorsal fin, and a single barbell on the lower jaw. The bowfin can be distinguished by a rounded tail, no scales on its head, and an eyespot near the tail in males.
PATHWAYS/HISTORY: The northern snakehead is native to areas of China, Russia, and Korea. In the United States, the snakehead was first discovered in 1977 within Silverwood Lake, California. In 2002, this species was discovered in a pond in Crofton, Maryland. This population was eradicated by state biologists using chemical treatments. Despite these efforts, in 2004 it was confirmed that snakeheads had become established in the Potomac River. The northern snakehead has also been reported in Florida, where it may be established. Specimens have been collected from a lake within a New York park; two ponds outside Philadelphia, Pennsylvania; a pond in Massachusetts; and reservoirs in California and North Carolina. In 2008, the northern snakehead was found in drainage ditches in Arkansas, as a result of a commercial fish farming accident. It is feared that recent flooding allowed the species to spread into the nearby White River, which would allow for the eventual population of the fish in the Arkansas and Mississippi Rivers.
Before their threat was fully appreciated, live snakeheads were openly sold in the United States in pet shops and live fish markets. This fish is popular in the Asian food market and most introductions were likely released for this purpose. Uninformed pet owners may have also released snakeheads into the wild when they grew too big for aquarium tanks, or as part of religious or cultural practices. In 2002, the import and interstate transport of the northern snakehead was banned without a permit from the U.S. Fish and Wildlife Service.
RISKS/IMPACTS: The impact northern snakeheads will have on U.S. waters is largely unknown. Like most other invasive species, these predatory fish compete with native species for food and habitat. Juveniles feed on zooplankton, insect larvae, small crustaceans, and the fry of other fish. As adults, they become voracious predators, feeding on other fish, crustaceans, frogs, small reptiles, and even birds and mammals. Snakeheads have the ability to breathe air by using an air bladder that works as a primitive lung, allowing them to survive for up to four days out of the water; they can survive for even longer periods of time burrowed in the sediment. This unique adaptation and their ability to travel over land to new bodies of water by wiggling their bodies over the ground, gives the snakehead a competitive edge over other fishes in securing habitat and expanding its range.
MANAGEMENT: The potential control methods for a snakehead infestation are limited, but vary with each specific infestation site. Physical removal of the fish using nets, traps, angling, electrofishing or biological control by introduction of predators are not likely to be successful for large infestations. If the infestation is believed to be limited to a few individuals the above techniques may be successful in removing the target organisms. However, even with a few individuals, it may be difficult to determine if the eradication was 100% successful. If the infestation is within an impoundment with water level control capability, removing all water may be a viable control technique. However, a water drawdown effort would result in damage to many desirable plant and fish species. An effort could be made to capture and relocate desirable species, but this would be an expensive and lengthy undertaking. Impoundments that are spring fed may be difficult to keep dry and the snakeheads may survive in the moist bottom sediments if any water is allowed to remain. Rotenone can be used to eradicate northern snakeheads from lakes and ponds; however, this chemical is not a selective piscicide and is effective against nearly all species of fish, native and non-native. The major drawback of treating with rotenone is the loss of native fish species along with the target species. Endangered species within a waterbody may be impacted by this technique. However, every fish species may be impacted by the introduction of northern snakeheads. In many cases, rotenone may be the only option to eradicate the population and ensure these fish do not spread to other waterbodies.
WHAT YOU CAN DO: Learn how to identify the northern snakehead. Your help is vital to report new sightings and to prevent their spread. Early detection of isolated populations may help slow or restrict the spread of the snakehead. If you find a snakehead fish, kill it and put it on ice, then contact your state’s Department of Natural Resources. General aquatic nuisance species prevention: Do not release aquarium pets or live food into the environment. Never dump live fish, e.g. baitbuckets, from one body of water into another body of water. Always drain water from your boat, livewell, and bilge before leaving any water access.
PROFILE CREDIT: Susan Pasko, NOAA and Anne Marie Eich, USFWS - IMAGE CREDIT: USGS