Thursday, April 27, 2017

Northern Snakehead


The Northern Snakehead is an air breathing, invasive fish species that is spreading throughout the United States. Introduced to United States waters by careless disposal of aquarium pets or by illegal stocking, the Northern Snakehead is a top predator.

The United States Fish and Wildlife Service determined that regulation of all snakehead species is necessary to protect native wildlife. On October 4, 2002, the entire snakehead family of fish (Channidae) including those currently recognized, and those that may be described in the future, was added to the injurious wildlife list described under the Lacey Act. Under this Act, it is illegal to import snakeheads into the United States or transport them across United States lines without permit. Permits for importation or interstate transportation can be obtained from the U.S. Fish and Wildlife Service Division of Management Authority (800-358-2104). Permits are issued for specific uses only, including medical or scientific research and education1. Anglers who catch Northern Snakehead are strongly encouraged to kill them immediately.

Two Department of the Interior (DOI) agencies are responsible for researching and regulating snakeheads. The first, a research branch of the DOI, is the United States Geological Survey (USGS; USGS scientists conducted detailed, worldwide research on snakeheads that provided the basis for regulating snakehead importation and interstate transport. Research funding was sponsored by another DOI agency, the U.S. Fish and Wildlife Service (FWS; The U.S Fish and Wildlife Service is responsible for fisheries management, regulations, law enforcement, and education. The mission of the FWS is to work with others to conserve, protect, and enhance fish, wildlife, and plants for the continued benefit of the American people. 2

Frankometer™ Factors –

Why So Feared? Why Banned?

Fankometer™ Defined

The Frankometer™ is an index used to express the threat level of a Frankenfish species. The Northern Snakehead is given a rating of 9 evil Frnakenfish. We stopped shy of 10 simply because expected devastation has not yet occurred.

Frankometer™ Factors for the Northern Snakehead


Range Expansion - Without vigilance and intervention, Northern Snakehead range expansion is almost certain.3 The Northern Snakehead has a broad latitudinal range and temperature tolerance suggesting that populations could be established throughout most of the continental United States and adjoining Canadian provinces.4


Natural Enemies – None. The Northern Snakehead is a top predator.

Voracity – The Northern Snakehead is a voracious predator.5

Indiscriminate Pallet – Northern Snakehead prey indescriminantly on all fish species in the waters in which they live. They also prey on crustaceans, aquatic insects (including worms), reptiles including snakes, frogs, tadpoles, small birds and mammals (Fuller 2009; Galveston Bay Invasive Species Risk Assessment Invasive Species Summary). Juvenile Northern Snakeheads feed in schools, with most of the activity during early evening and again in early morning, usually in vegetation close to shore (Courtenay and Williams 2004).6

Aquatic Ecosystem Alteration – Because the Northern Snakehead has no natural predators, can survive in most aquatic environments, is prolific, and is voracious, it could cause permanent alteration of aquatic ecosystems throughout the United States and Canada.

Threat to Endangered Species – Of all endangered species in United States aquatic habitats, 115 fish, sixteen amphibians, and five crustaceans are at high risk of severe impact by predacious snakeheads.7

Exotic (Disease Causing) Pathogens – Invasive species often carry and introduce exotic pathogens, against which native species have no resistance. Further, Northern Snakehead, acting as hosts, could easily contribute to the propagation of the pathogen.

In 2006, a filterable and probably viral agent was found in a number of Northern Snakehead of the Chesapeake Bay Watershed. Scientists are working to determine the following:

 • Positively identify the “putative viral isolate”
 • Determine the isolate’s range
 • Whether or not the agent causes disease in Northern Snakehead
 • If the agent causes disease in native species
 • If the agent arrived with the introduction of the Northern Snakehead or if the agent is a native pathogen8

The Northern Snakehead and species native to United States waters are impacted by the following parasites:

 • Mysosoma acuta (also affects crucian carp)
 • Henneguya zschokkei (also affects salmonids)
 • Cysticercus gryporhynchus cheilancristrotus
 • (also affects cyprinids, perches)
 • Clinostomum complanatum (also affects perches)
 • Paracanthocephalus cutus (also affects cyprinids, escocids, sleepers and bagrid catfish)

(For more information regarding parasites carried by Northern Snakehead, see Courtenay & Williams 2004).9


Once established in an aquatic ecosystem, the Northern Snakehead is almost impossible to exterminate. Here’s why…

High Fertility Rate

Long Lifespan – Northern Snakehead can live for up to eight years.10

Withstands Freezing – The Northern Snakehead can withstand freezing temperatures11 by hibernating.12

Tolerates Poorly Oxygenated Water– Northern Snakehead can survive in poorly oxygenated water, giving them a competitive advantage over species such as pike and bass that require higher oxygenation (Sea Grant Pennsylvania 2007).13

Goes Dormant – During drought, the Northern Snakehead goes dormant in mud. The moisture of the mud is sufficient to keep the Northern Snakehead alive.14

Tolerates Absence of Water – The Northern Snakehead can tolerate the absence of water for up to four days15 by breathing with an air bladder that works as a primitive lung. This bladder is not found in most fish.16

Ambulation – The Northern Snakehead is capable of moving short distances on land using its pectoral fins.17 Ambulation allows the Northern Snakehead to migrate from one body of water to another during times of drought or food shortage.

Economic Threat

Economic/Livelihoods – In 2008, the US Fish and Wildlife Service and the Arkansas Game and Fish Commission suggested that the economic impact of the Northern Snakehead might be significantly negative if it became established throughout the Mississippi River basin.18

The concern is that the Northern Snakehead could decimate native fish populations fishermen currently depend upon for their livelihoods.

Lacy Act

In October 2002, the US Fish and Wildlife Service passed the Lacy Act, banning ALL snakeheads from importation and interstate transport. Further, all Snakehead species are included on the Federal Prohibited Fish, Mollusks, and Crustaceans list. The list encompasses all “taking, possession, transportation, sale, purchase, barter, exportation, and importation of wildlife and plants”.19

 (a) Upon an exporter filing a written declaration with the District Director of Customs at the port of entry as required under 14.61 of this chapter, live or dead fish, mollusks, and crustaceans, or parts thereof, or their gametes or fertilized eggs, may be imported, transported, and possessed in captivity without a permit except as follows: (1) No such live fish, mollusks, crustacean, or any progency (the immediate descendant or descendants of ) or eggs thereof may be released into the wild except by the State wildlife conservation agency having jurisdiction over the area of release or by persons having prior written permission from such agency.

 (b) The importation, transportation, or acquisition of any of the species listed in this paragraph is prohibited except as provided under the terms and conditions set forth in 16.22: (i) Live fish or viable eggs of walking catfish, family Clariidae; (ii) Live mitten crabs, genus Eriocheir, or their viable eggs; (iii) Live mollusks, veligers, or viable eggs of zebra mussels, genus Dreissena; and (iv) Any live fish or viable eggs of snakehead fishes of the genera Channa and Parachanna (or their generic synonyms of Bostrychoides, Ophicephalus, Ophiocephalus, and Parophiocephalus) of the Family Channidae, including but not limited to: (A) Channa amphibeus (Chel or Borna snakehead).20

Fisherman Responsibility

Fisherman are urged to kill and freeze all snakeheads, regardless of species, and report all sightings and catches to the USGS at


Class Actinopterygii
   • Subclass Neopterygii
      • Order Perciformes
         • Suborder Channoidei
              • Family Channidae
               • Group Fishes
                  • Genus Channa
                     • Species Agus
                        • Common Name Northern Snakehead


1. Channa argus argus (Cantor, 1842)
2. Ophicephalus argus kimurai (Shih, 1936)
3. Ophicephalus argus warpachowskii (Berg, 1909)
4. Ophicephalus argus (Cantor, 1842)
5. Ophicephalus nigricans, Ophicephalus pekinensis (Basilewsky, 1855)21

Northern Snakehead – Alternative Names

The Northern Snakehead is indigenous to many places in Asia, and has been introduced to countries around the world. Below is a list Northern Snakehead common names.

1. Amur snakehead (English)
2. Eastern snakehead (English)
3. Ocellated snakehead (English)
4. Amurinkäärmeenpää (Finnish-Finland)
5. Idänkäärmeenpää (Finnish-Finland)
6. Amur-Schlangenkopf (German-Germany)
7. Cabeza de serpiente (Spanish-Spain),
8. Ga mul chi (Korean)
9. Her-yu (Chinese-China)
10. Kamuruchi (Japanese)
11. Raigyo (Japanese)
12. Kinesisk slangehovedfisk (Danish-Denmark)
13. Poisson tête de serpent (French-France)
14. Zmeegolov (Russian)22


Native Range

The Northern Snakehead’s native range includes:

1. China: (from Yunnan to Peking, the Liao, Yalu, and Lianzi Lakes, and upper reaches of the Beijiang in Guangdong Province)
2. Russia (the Ussuri River and the lower reaches of the Amur)
3. Korea – All of Korea except for the northeastern regions (FishBase 2009).23

Alien Range

Mostly through stocking, the Northern Snakehead populates rivers, lakes and ponds in these countries:

1. Asia
2. Cambodia
3. Canada
4. China
5. Czech Republic
6. Europe
7. Hong Kong
8. India
9. Indonesia
10. Japan
11. Kazakhstan
12. Nigeria
13. Russian Federation
14. Slovakia
15. Switzerland
16. Thailand
17. Turkmenistan
18. United States (USA)
19. Uzbekistan
20. Viet Nam (Vietnam)24

United States Introduction

The first report of the Northern Snakehead in the United States came from Silverwood Lake, California in 1977.25

Fish Farming: The Northern Snakehead was cultured on three Arkansas fish farms until prohibited by the Arkansas Fish and Game Commission in August 2002 (Courtenay & Williams 2004).

Hunting/fishing: The Northern Snakehead was introduced to many locations for sport fishing (Courtenay & Williams 2004).

Internet sales/postal services: Though illegal, hobbyists and importers can purchase Northern Snakeheads from numerous Internet vendors (Courtenay & Williams 2004).

Live food trade: Many introductions of the Northern Snakehead are suspected to be the result of intentional release of fish obtained for the live food trade (Courtenay & Williams 2004).

Pet/aquarium trade: Some introductions are believed to be the result of intentional release of aquarium fish that have become too expensive to feed or have outgrown their aquaria (Courtenay & Williams 2004).26

Northern Snakehead – United States


Northern Snakehead Sightings Distribution

This map layer is a compilation of confirmed Northern Snakehead reports in the United States from 1997 through 2010. It is updated daily.
It provides geographical and historical information to show distribution
over space and time. The reports came primarily from State agencies in the region. The locations of confirmed sightings were registered at 1:100,000-scale on EPA Reach File Version 3.0 and are maintained as an ArcInfo shapefile. These data are intended for geographic display and analysis at the national level, and for large regional areas. Sightings were reported with varying levels of accuracy.
Some of the reports were as latitude-longitude coordinates, some as
river miles, and others as just a lake, beach, harbor, or a water body and nearest town name. If no specific location was reported in a lake, the point was assigned to the center. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the U.S. Geological Survey in the use of these data.

Northern snakeheads are represented with larger red markers. Click on a marker for more information. To REPORT an observation or collection of snakeheads, click here.

Suggested citation: Benson, A. J. 2010. Northern snakehead sightings distribution.
Retrieved 12/4/2010 from

For more information, contact: Amy Benson,

References to non-U.S. Department of the Interior (DOI) products do not constitute an endorsement by the DOI.
By viewing the Google Maps API on this web site the user agrees to these TERMS of Service set forth by Google.

Know the Difference

The Northern Snakehead is often mistaken for other species native to North America. Below is a description of the Northern Snakehead and similar looking species.

Northern Snakehead Description

The Northern Snakehead grows to about 85 cm (about 33 inches). Males tend to be larger than females. Northern Snakeheads have small, scaled snakelike heads. They have large mouths with sharp teeth (similar to those of pike or pickerel). Their bodies are cylindrical with tapering toward a short tail. They have a single, long dorsal fin and a long anal fin. There is a dark stripe from just behind the eye to the upper edge of the operculum with another dark stripe below from behind the orbit extending to the lower quadrant of the operculum. Along their sides, Northern Snakeheads have dark irregular blotches on a background of golden tan to pale brown (Sea Grant Pennsylvania 2007). Northern Snakeheads are capable of darkening their golden tan to pale brown background, almost obscuring the blotches. Unlike other snakehead species, Northern Snakehead fry coloration is substantially similar to that of adults.27

A very hardy species, the Northern Snakehead inhabits freshwater within a temperature range of 0 to 30°C. They prefer stagnant, shallow ponds, streams, canals, reservoirs, lakes, rivers or swamps with mud substrate and vegetation.28


The Bowfin is tan-olive, with dark olive reticulation. Its body is somewhat elongated, and it has a long dorsal fin and bony scales. Small canine and peg-like teeth fill its mouth. There is a yellow rimmed, black spot at the caudal peduncle which tends to be more prominent in males.

The Bowfin are a predatory species that generally eat fish, aquatic invertebrates and frogs Bowfin grow to a maximum length of about 32 inches.

Typically associated with swamps and sluggish open marsh-fringed rivers, Bowfin are found waters of all depths. They are a nocturnal species, but most active at dusk and dawn.

Like the Northern Snakehead, Bowfin are capable of breathing surface air using an air bladder as a lung. Also like Northern Snakehead, Bowfin are able to withstand droughts by going dormant in the mud.29

American Eel
Typically found in mountain streams, lakes and estuaries, the American Eel grows to about 40 inches. Its body is very elongated. It has long dorsal and anal fins, converging with the caudal fin to create the appearance of one continuous fin. It does not have a pelvic fin. It has small teeth.

The American Eel coloration may be

• olive-brown
• yellow-olive
• almost black

There is normally a silver sheen on lower side.30

Sea Lamprey

The Sea Lamprey has an eel-like body and grows to 12-20 inches. Its back is typically dark brown or black. Its belly is typically light yellow or pale brown. They have large reddish eyes. They have circle shaped mouths with numerous teeth.31

Interestingly, while the Sea Lamprey, is native to the coastal waters of the Eastern United States, it is considered an invasive species to the Great Lakes.


Northern Snakeheads reach sexual maturity by two to three years of age and when they grow to a length of about 30 centimeters. Females produce eggs up to five times each year and release 22,000 to 51,000 eggs per spawn (Frank 1970, Nikol’skiy 1956, in Courtenay and Williams 2004). Annually, females lay as many as 100,000 eggs. Fertilization is external and occurs in early morning in shallow water nests. The eggs float, are pelagic, spherical, non-adhesive, yellow, and about two millimeters in diameter. Hatching takes about 28 hours at 31°C and 45 hours at 25°C. Eggs can hatch at lower temperatures but the time to hatch is usually considerably longer (Courtenay and Williams 2004). Adults care for their young which feed on plankton until they are about four weeks old.32

Lifecycle stages

Northern Snakehead larvae are about 4.5 millimeters long. Within two weeks of hatching, fry yolk sacks are absorbed, their fin rays are noticeable, they grow to a length of about eleven millimeters and are black. Within four weeks of hatching, fry grow to about two centimeters. Their pelvic fins are developed, their epibranchial breathing cavities are functional and their coloration is brown. Also at about four weeks, fry no longer behave in aggregate and move to deeper waters. Scales develop at a length of about four centimeters.33

Juvenile northern snakehead, about 4 cm long, captured from pond in Crofton, Anne Arundel County, Maryland, July 9, 2002. Photo by Algerina Perna; reproduced with permission of the Baltimore Sun.



3USGS NAS Fact sheet


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Snakehead Fingerlings Feeding

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