By: Brad J.B. - UNCG

Northern Snakehead Taxonomy

Snakeheads belong to the order Perciformes, family Channidae. There are currently 29 snakehead species within the family Channidae (Courtenay and Williams, 2004). 26 of them are of the genera Channa (which includes the Northern Snakehead and other snakeheads native to Asia, Malaysia and Indonesia), while three are of the genus Parachanna (African snakeheads) (Courtenay and Williams, 2004, USFWS, 2002). The Northern Snakehead, species Channa argus, is one of four species of snakehead known to have been introduced into the US. The other species are C. marulius (Bullseye Snakehead), C. micropeltes (Giant Snakehead), and C. maculata (Blotched Snakehead) (USFWS, 2003). There are also 2 sub-species of C. argus: C. argus argus, and C. argus warpachowski (Global Invasive Species Database, 2004).

Snakehead Physical Characteristics and Biology

In general, the Northern Snakehead is very similar to other Channa species, having a relatively long, cylindrical body (up to 1.2 m, 6.8 kg) and enlarged scales on the head (from which the common name snakehead was derived). Northern Snakeheads also have large mouths with protruding lower jaws that contain sharp, “canine-like teeth” (USFWS, 2002). They have “long dorsal and anal fins [and] dark irregular blotches along their sides, pelvic fins located beneath the pectorals, and truncate (not rounded) tail” (USFWS, 2003)

Snakeheads are capable of breathing atmospheric oxygen and may survive out of water for 3-4 days. They can migrate slowly over land by wriggling their bodies and pushing with their tail fins (Hilton, 2002). The Northern Snakehead is an apex predator that feeds upon a wide variety of animals. Adult Snakeheads primarily eat other fish, while juveniles eat crustaceans, insects, and plants (USFWS, 2002, 2003). Snakeheads can be typically found in muddy or vegetated freshwater ponds, slow-moving streams, and swamps. They can also live in water ranging from 0 to 30 C°, though their optimum temperature for growth is about 26 C° (Liu and Cui, 1998). Spawning typically occurs up to five times a year from June to August. Snakehead pairs may remain monogamous for one or more spawning seasons. Females may lay 50,000 or more eggs per year. Snakeheads build nests by clearing a small circular section (usually 1m in diameter) of aquatic vegetation. This provides a fairly secure vertical column of water that the eggs are laid in. Snakehead eggs are buoyant and rise to the top of the water column, where they are “vigorously guarded by one or both parents” (Courtenay and Williams, 2004). Juveniles become sexually mature at 2 years, about 30 cm long (Hilton, 2002). Length of maximum lifespan is still unknown.

Where Are They From?

The Northern Snakehead (Channa argus) is native to the freshwater lakes of China and Korea. A subspecies, C. argus warpachowski, is native to the Armur River of Russia and China. However, since the 1960's, this subspecies has become widespread in the Aral Sea basin and adjoining rivers (Hilton, 2002).

How did they get here?

It is likely that the Northern Snakehead (along with three other snakehead species) entered the United States through two main pathways:

1. Intentional releases by pet owners: It is possible for nearly anyone to acquire snakeheads through the Internet or in pet stores. Once the owner no longer wants the fish, or can no longer care for it, they are simply dumped into local lakes and rivers (USFWS, 2002). The snakehead caught in Lake Michigan is believed to an example of this practice.

2. The live food fish trade: Snakeheads are still being sold live at fish markets and in some restaurants in Boston and New York. As with neglectful pet owners, it is believed that some of the fish in the live fish trade are being intentionally released (USFWS, 2002).

Current Distribution

In addition to their native range, which includes China, Russia, and Korea, Northern Snakeheads have been found in the following places as well:

The United States:

California (1997)

Florida (juveniles found, 2000)

Maryland (juveniles found, 2002)

Massachusetts (2001)

North Carolina (2002)

Pennsylvania (2004)

Virginia (juveniles found, 2004)

Illinois (2004)

Additionally, snakehead confiscations and investigations into snakehead-related illegal activities have occurred in the states of Alabama, Arkansas, Kentucky, Texas and Washington (Courtenay and Williams, 2004).

They are also found in parts of: Japan (early 1900s)
Central Asia (Kazakhstan, Uzbekistan, Turkmenistan)
Eastern Europe (Russia, Czechoslovakia, 1950s)
Philippines
Madagascar




Associated Problems

Highly predatory. Northern Snakeheads are capable of disrupting entire food webs by consuming a large quantity and variety of prey, including other fish, amphibians, crustaceans, insects, zooplankton, and occasionally aquatic birds and small mammals. This can cause changes in the feeding pattern and food availability for other organisms in the ecosystem (USFWS, 2003). To compound the problem, the adult snakehead has no known natural predators in the US.

High fertility and parental care.Female snakeheads can lay as many as 50,000 eggs per year (1,300 to 15,000 eggs per spawn). The parents aggressively protect their young until they are about 18mm in length (after about 1 month of development). After this time, the juvenile snakeheads have developed fins, and are capable of fending for themselves (Berg, 1965, Courtenay and Williams, 2004).

Low oxygen requirement. Northern Snakeheads do not require high levels of dissolved oxygen. Thus, they tend to have a competitive advantage over fish that require more dissolved oxygen, such as trout, pike, and bass (USFWS, 2003).

Wide dispersal. They are capable of breathing atmospheric oxygen and can remain out of water for 3 – 4 days at a time (Agbayani, 2004). They can also move over land by wriggling their body and moving their fins. These physiological adaptations allow them to travel short distances over land, from one freshwater body to another (Hilton, 2002).

May spread disease. Northern Snakeheads may be able transfer pathogens to native fish, such as Epizootic Ulcerative Syndrome (USFWS, 2002).

Current Solutions

By August 2002, 14 states had already banned the possession of live snakeheads.

All 28 species of snakeheads (including C. argus) were listed as injurious fish under the Lacey Act in October 2002, which prohibited the interstate transport and importation of snakeheads. They are no longer found in pet shops or in the live food fish markets of New York and Boston (Courtenay and Williams, 2004).

The herbicides Diquat Dibromide and Glyphosate were applied to a pond in Crofton, Maryland in May 2002. Several adults and at least 100 juvenile snakeheads were captured from the pond prior to the treatment of herbicides. The herbicides dramatically lowered the oxygen level in the pond, killing many fish. Two weeks later, Rotenone, a natural insecticide, was applied to the pond in order to kill any snakeheads that might have survived A few weeks later, a sampling of the pond indicated that water quality levels had returned to normal and no Snakeheads were found (Hilton, 2002).

Similar eradication is likely to be much more difficult in rivers (such as the Potomac River, where they were found in the spring of 2004), streams and large lakes (Global Invasive Species Database, 2004).

Literature Cited

Agbayani, Eli. Channa argus argus Snakehead (2004). Available at http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=4799&genusname=Channa&speciesname= argus%20argus. (10 December 2004)

Berg, L.S., 1965. Freshwater fishes of the U.S.S.R. and adjacent countries. Vol. 3. Israel Program for Scientific Translations, Jerusalem. pp. 76-77.

Courtenay, W.R., Jr., and J.D. Williams. 2004. Snakeheads (Pisces, Channidae): A biological synopsis and risk assessment. U.S. Geological Survey Circular 1251. Availiable at http://fisc.er.usgs.gov/Snakehead_circ_1251/html/title.html (10 December 2004).

Cui, Y., and J. Liu. 1998. Food consumption and growth of two piscivorous fishes, the mandarin fish and the Chinese snakehead. Journal of Fish Biology 53 (5):1071-1083.

Global Invasive Species Database. Channa argus (fish) (2004). Available at http://www.issg.org/database/species/ecology.asp?si=380&fr=1&sts=sss (12 December 2004)

U.S. Fish and Wildlife Service. Invasive Species Program Snakeheads – The Newest Aquatic Invader (2002). Available at http://biology.usgs.gov/invasive/factsheets/SnakeHeadFish.pdf. (5 December 2004).

U.S. Fish and Wildlife Service. Recognizing Northern Snakehead (2003). Avaliable at http://midwest.fws.gov/fisheries/library/fact-snakehead.pdf. (5 December 2004).

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