Animal Diversity Web

Geographic Range

Channa argus, commonly known as northern snakehead, is native to river drainages to the Pacific in east Asia, from Heilong (Amur) River basin, Ussuri River basin, and Lake Khanka on the Russian-Chineses border south to the upper reaches of the Yangtze River in China. in in Korean and Chinese rivers in between. The species has been widely introduced, to Japan and central Asia (rivers in Kazakhstan, Uzbekistan, Turmenistan), and into eastern North America. In North American the first northern snakehead nest was found in Crofton Pont in Maryland and since then, northern snakehead populations have been found in the Hudson River (New York), the Chesapeake Bay area of Virginia and Maryland, and also in Pennsylvania and Florida. The Potomac River system in Virginia has also been a regularly reoccurring location of northern snakehead since 2002, with introductions estimated as early as 1998. Smaller populations have been found as far west as the Mississippi River in Arkansas. (Courtenay and Williams, 2004; Lapointe, et al., 2013; Lapointe, et al., 2010)

• Biogeographic Regions
• nearctic
  • introduced
• oriental
  • native

Habitat

Northern snakeheads freshwater fish, found in many types of freshwater habitats, from lakes and ponds to slow-moving rivers and streams, as well as swamps and marshes of sufficient depth. Their preferred habitats are shallow still or slow-moving waters with mud bottoms and plenty of aquatic vegetation. This is the most cold-tolerant species in the family Channidae, it can survive under ice, in temperatures from 0 - 30 degrees Celsius, and possibly higher. Snakeheads are air-breathers, so can persist in waters with very low oxygen levels. Northern snakeheads also are capable of survival in nearly every freshwater habitat system due to their ability to air breathe. Recent observations of the introduced population in the Potomac River in North America indicate tolerance of up to 15-18 ppt salinity. The main habitat preference of the northern snakehead is shallow waters typically less than 2.5m. However, the species has been understood to cross deep waters in order to reach spawning areas. (Courtenay and Williams, 2004; Lapointe, et al., 2013)

• Habitat Regions
• temperate
• freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools
• brackish water

• Wetlands
• marsh
• swamp

• Other Habitat Features
• riparian
• estuarine

• Range depth

  0.5 to 3 m

  1.64 to 9.84 ft

• Average depth

  2 m

  6.56 ft

Physical Description

Northern snakeheads have long slender bodies, and a flattened head with eyes that are located on the front of the head. The head has a large mouth with a protruding lower jaw. The fish also have very sharp teeth, located in their lower jaw. Northern snakeheads have dorsal and anal fins that are elongated and span nearly half of the ventral posterior portion of the body, or the bottom side of the fish’s body located closer to the tail fin. Also, the fish has small pelvic fins that are located directly behind their pectoral fins that are located on either side of the snakeheads’ head. The northern snakehead has approximately 8 rows of scales above, and 12 rows of scales below their lateral line. Northern snakeheads change color as they mature. As they are in their youth the most common color scheme is a golden brown to pale gray color. Once mature, northern snakeheads are typically a darker brown with dark brown-red blotches covering the entire body. Fully mature northern snakeheads range from 44 cm to 72 cm. However, in some locations northern snakeheads have been found to grow up to 150 cm and weigh nearly 8 kg. Females tend to be smaller than males, and have a shorter dorsal fin along with smaller snout and upper jaw.

In North America, northern snakehead can be mistaken for native species, such as the bowfin (Amia calva) and burbot (Lota lota). American bowfin pelvic fins are located further back on the body, whereas the northern snakeheads’ pelvic fins are located directly behind the pectoral fins. Also the bowfin has a divided dorsal fin, with the northern snakehead dorsal fin is a single long structure. The primary difference between northern snakehead and burbot is that the burbot has barbels similar to a catfish, also the burbot’s anal fin is quite short compared to the long anal fin of a northern snakehead. (Courtenay and Williams, 2004; Lapointe, et al., 2013; Wang, et al., 2012)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger

• Range mass

  2 to 8 kg

  4.41 to 17.62 lb

• Average mass

  4 kg

  8.81 lb

• Range length

  44 to 150 cm

  17.32 to 59.06 in

• Average length

  70 cm

  27.56 in

Development

Once hatched, northern snakeheads begin to grow rapidly. Pectoral fins develop one day after hatching, and as soon as day three external blood vessels will be reduced and respiration by gills begins. Now, around 7mm in length and very dark in color, the fish begin to feed on other substances besides their yolk sacs. At this point, the fish mainly feed on plankton. After two weeks, the yolk sac has completely disappeared and fin rays start to become visible in the pectoral fins. At this time the fish will be between 1 -2 cm in length and will fully develop their epibranchial breathing cavities, allowing the fish to air breathe. At this stage in development the snakehead’s color will change from black to brown, and the fish will be ready to move to deeper water. Scales develop when the fish reach a length of 4cm. At this point the diet of the northern snakehead consists mainly of small fish and crustaceans. Northern snakehead are classified as exhibiting indeterminant growth, meaning that they continue to grow their entire lives. Depending on whether or not the fish is in its native range, greatly influences its growth rate after the initial growth period. In the Huanghua Lake, a native region for northern snakeheads, the fish were observed to grow to a length of 637mm by age five. In the Potomac River system (an introduced habitat), the average length of northern snakeheads at five years was only 529mm. (Courtenay and Williams, 2004; Landis, et al., 2011)

• Development - Life Cycle
• indeterminate growth

Reproduction

Both male and female northern snakeheads help to build a nest in shallow, stagnant water when spawning. They first clip vegetation in order to create a circular nest, then the female lays free- floating eggs at the top of the nest. The eggs are able to float in water because of their large lipid droplet that surrounds the yolk sac. The male then fertilizes the eggs by swimming over them and releasing his sperm. The parents guard the young until they reach their juvenile period, and are able to swim to deeper waters. Northern snakeheads spawn multiple times per year, with different partners. (Courtenay and Williams, 2004; Landis, et al., 2011)

• Mating System
• polygynandrous (promiscuous)

Northern snakeheads’ reproductive habits largely depend on whether the fish is located in an introduced or native habitat. In its native range, in areas such as the Amur River, northern snakeheads have been observed spawning up to five times a year. In introduced ranges such as the Potomac River or in Kazakhstan, northern snakeheads have been observed spawning only one to three times per year. Also, northern snakeheads are capable of spawning at an age of two to three years in their native ranges, and younger than two years in their introduced ranges. In the spawning season, a male and female build an aquatic nest, in shallow slow moving waters, composed of plants that the parents clear of any debris or dirt prior to spawning. The female northern snakehead releases her eggs on top of the nest, and the male comes behind her to fertilize the eggs. Multiple studies report a wide range of eggs per female, varying from 1,300 – 15,000 eggs in one spawning session. Northern snakehead eggs were described by Soin ([1960], as cited by Courtney and Williams, 2012) as yellow, spherical, non-adhesive, and around 2mm in diameter. Depending on the temperature of the water, the eggs can hatch in as little 28 hours in 31 degree water, but can take as long as five days in cooler waters (ca. 18 degrees Celsius). (Courtenay and Williams, 2004; Landis, et al., 2011; Wang and Yang, 2011)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • external
• oviparous

• Breeding interval

  Northern snakeheads can breed up to 5 times a year

• Breeding season

  Peak spawning is in June and dwindles into October

• Range number of offspring

  1,300 to 15,000

• Average number of offspring

  7,300

• Range time to hatching

  28 to 120 hours

• Average time to hatching

  45 hours

• Range time to independence

  3 to 6 weeks

• Average time to independence

  4 weeks

• Range age at sexual or reproductive maturity (female)

  2 to 4 years

• Range age at sexual or reproductive maturity (male)

  2 to 4 years

Both parents guard the young until around four weeks after hatching, when the fish reach a length of 2 cm and are able to move to deeper water. Both parents guard the newly hatched, by creating a circular perimeter. The female closely guards the nest and the male circles the nest, occasionally taking breaks for respiration. (Courtenay and Williams, 2004; Landis, et al., 2011)

• Parental Investment
• male parental care
• female parental care
• pre-hatching/birth
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • male
    • female

Lifespan/Longevity

Northern snakeheads are known to live for 3-6 years in the wild, and the oldest recorded age for a wild northern snakehead was seven years old according to otolith readings from the Potomac River system. In their natural range northern snakeheads have a very similar lifespan; however the oldest documented fish in its natural range was eight years old. (Courtenay and Williams, 2004; Landis, et al., 2011; Odenkirk, et al., 2013; Wang and Yang, 2011)

• Average lifespan
  Status: wild

  8 years

• Typical lifespan
  Status: wild

  3 to 8 years

• Average lifespan
  Status: wild

  5-6 years

Behavior

Northern snakeheads are active mostly at late dusk and into the early night. This is when the species prefers to feed, often in schools that hunt in aquatic vegetation close to the shore. The species is known to be very aggressive towards their prey, and have even been called “voracious feeders” by Okada (([1960], as cited in Courtney and Williams, 2004). Shoaling is a common practice performed by the northern snakehead. Species dominance is established by aggressiveness that is demonstrated through biting and chasing. The species appears to be social, in that they prefer to hunt together, and only in extreme cases, such as low food source, will the species disperse.

Due to northern snakeheads' ability to breathe out of the water, it has been observed that the fish is capable of making its way across small gaps of land. The pectoral fin of the northern snakehead lacks any bony structure, so the fish cannot thrust itself forward. It instead relies on an eel-like motion, and cannot cross large distances.

A study was conducted to show if northern snakehead were capable of thriving in Czechoslovakia. The snakeheads were placed into three ponds, each containing a different native fish, to determine which the snakeheads preferred the most. At the end of the study, after the vegetation and water was removed from the ponds, it was noted that the snakeheads buried themselves in the mud in the bottom of the pond for survival. (Courtenay and Williams, 2004; Landis, et al., 2011; Wang and Yang, 2011)

• Key Behaviors
• natatorial
• crepuscular
• motile
• sedentary
• social

• Range territory size

  1.2 (low) km^2

Home Range

Northern snakeheads tend to disperse after they are old enough to endure deeper water and stronger currents. Adults are quite mobile, unless they are guarding their young. When guarding their young the home range averages 1.2 square kilometers. However, the distance of dispersal is largely dependent on the season. The highest average dispersal distance being directly after the spawning season, and the shortest dispersal was during the actual spawning season. Northern snakeheads were tagged in the Potomac River system to determine the home ranges of 42 fish. On average the fish dispersed up to 18 km, and one fish was recaptured 21 km from where it was originally tagged. (Courtenay and Williams, 2004; Lapointe, et al., 2013)

Communication and Perception

Northern snakeheads are capable of producing a small array of noises. Mature northern snakeheads have been observed making grunting noises as they feed, and clicking noises as they rise to the surface to breathe. Northern snakeheads also have good eyesight. They prefer to hunt in low light situations, and have even been known to attack insects and other non-aqueous animals that they see outside of the water (e.g., on low lying tree limbs). Northern snakehead are also capable of chemical perception. Snakeheads can perceive when there is a wounded animal in nearby waters, or if there is a current feed taking place by smelling chemical traces of blood in the water. (Courtenay and Williams, 2004; Landis, et al., 2011)

• Communication Channels
• visual

• Other Communication Modes
• vibrations

• Perception Channels
• visual
• tactile
• vibrations
• chemical

Food Habits

The northern snakehead is a predatory fish species that feed mostly on other fish, frogs, freshwater crustaceans, and some insects. As juvenile fish, the northern snakehead commonly feeds on small crustaceans and other fish larvae. A study conducted by Dukravets and Machulin ([1978], as cited in Courtney and Williams, 2012) showed that the fish would feed on other fish up to 33% of their own body size. The northern snakehead becomes predominately carnivorous when they reach 4cm in length. Once fully mature, other fish make up to 90% of the northern snakeheads’ diet. In their introduced range, specifically in the Potomac River system, northern snakeheads have been found to prey upon banded killifish (Fundulus diaphanous), white perch (Morone americana), pumpkinseed fish (Lepomis gibbosus), bluegill (Lepomis macrochirus) and goldfish (Carassius auratus). In their native range, some of the fish that northern snakeheads prey include perch (Perca fluviatilis), carp (Cyprinus carpio), bream (Abramis), and loach (Cobitis). Once seasonal water temperatures reach 10 degrees the northern snakeheads become fully active in their feeding habits. Northern snakeheads feed in schools, as many other snakehead species do, and prefer to hunt in low light scenarios. (Courtenay and Williams, 2004; Odenkirk, et al., 2013; Saylor, et al., 2012)

• Primary Diet
• carnivore
  • piscivore
  • insectivore
  • eats non-insect arthropods
• planktivore

• Animal Foods
• amphibians
• reptiles
• fish
• eggs
• insects
• aquatic crustaceans

Predation

Outside of humans (Homo sapiens), northern snakeheads are not prone to predation. In areas of China, the northern snakehead is farmed, and is the most commonly found snakehead species found in many of China’s fish markets.

It is likely that any large fish-eating predator in their habitats might prey on them, such as larger fish, birds, crocodilians, turtles, otters, etc. Large adult northern snakeheads are large enough that they may be the top predators in some habitats. In one study eastern mosquitofish, (Gambusia holbrooki), were observed eating newly fertilized eggs in a northern snakehead nest. Channa eggs and fry are small enough to be attacked by aquatic invertebrate predators too, such as dragonfly nymphs (Odonata) or predaceous diving bugs (Belostomatidae), if not protected by their parent.

The coloration pattern of these fish is probably cryptic, but this has not been shown experimentally. (Courtenay and Williams, 2004; Landis and Lapointe, 2010)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • Human Homo sapiens
  • eastern mosquitofish Gambusia holbrooki

Ecosystem Roles

Newly hatched snakeheads feed on insect species until they reach a length of around 2 cm. As a result of this, they likely help to keep the number of many pest related insects at bay. However, once they are big enough to become carnivorous, other fish make up more than 90% of their diet.

Northern snakeheads are an invasive species that could cause ecosystem disruption to their non-native environment. They have the potential to disrupt native aquatic foodwebs, by competing with native fish for prey and feeding directly on native fish, including desirable game fish.

Like most fish, northern snakeheads are also affected by several parasites, including myxozoans, tapeworms (including Cysticercus, Gryporhynchus cheilancristrotus), trematodes such as Clinostomum complanatum and Posthodiplostomum, and acanthocephalans including Paracanthocephalus cutus. (Courtenay and Williams, 2004; Landis and Lapointe, 2010; Nguyen, et al., 2012)

Economic Importance for Humans: Positive

In their native range, northern snakeheads are raised in commercial aquaculture for food. It is the most important snakehead species in China, and an estimated 500 tons are produced yearly, for food, in Korea. It is also stocked in many of its native ranges in order to be cultured as a sport fish. Also, in Europe and Japan, northern snakeheads are valued as pets and aquarium owners purchase them for this reason. (Courtenay and Williams, 2004)

• Positive Impacts
• pet trade
• food

Economic Importance for Humans: Negative

In the United States and other introduced ranges, northern snakeheads have a negative economic impact. They are known to deplete many freshwater game fish species, such as the largemouth bass, Micropterus salmoides, in the Potomac River system. Government agencies in the U.S., Canada, and other countries are working to control the spread of the species. (Courtenay and Williams, 2004; Gul, et al., 2011; Poulos, et al., 2012)

Conservation Status

The IUCN has not yet evaluated the conservation status of northern snakeheads. Given their wide range, and popularity in aquaculture, they are not in immediate danger, but native wild populations might be vulnerable. In the United States, Channa argus is considered an injurious species, and state and Federal agencies are working to eliminate small populations and prevent its spread. (Courtenay and Williams, 2004; Landis and Lapointe, 2010; Orrell and Weigt, 2005)

• IUCN Red List

  Not Evaluated

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Comments

All species of snakeheads (Channidae) are listed by the U.S. Fish & Wildlife Service as injurious species, and it is illegal to import live specimens into the U.S., or to transport them across state lines within the U.S. The FWS and state agencies urge anyone that catches a snakehead in the U.S. to keep it, freeze it, and report it to their local fish and game agency.

Contributors

Jeffrey Whedbee (author), Radford University, Karen Powers (editor), Radford University, George Hammond (editor), Animal Diversity Web Staff.

References

Adamson, E., D. Hurwood, P. Mather. 2010. A reappraisal of the evolution of Asian snakehead fishes (Pisces, Channidae) using molecular data from multiple genes and fossil calibration. Molecular Phylogenics and Evolution, 56: 707-717.

Courtenay, W., J. Williams. 2004. "Snakeheads (Pices, Channidae)- a biological synopsis and risk assessment" (On-line pdf). USGS. Accessed January 27, 2017 at https://pubs.er.usgs.gov/publication/cir1251.

Gul, Y., Z. Gao, X. Qian, W. Wang. 2011. Haematological and serum biochemical characterization and comparison of wild and cultured northern snakehead (Channa argus Cantor,1842). Journal of Applied Ichthyology, 27: 122-128.

Herborg, L., N. Mandrak, B. Cudmore, H. Maclsaac. 2007. Comparative distribution and invasion risk of snakehead (Channidae) and Asian carp (Cyprinidae) species in North America. Canadian Journal of Fisheries and Aquatic Sciences, 64: 1723-1735.

Landis, A., N. Lapointe. 2010. First record of a northern snakehead (Channa argus Cantor) nest in North America. Northeastern Naturalist, 17/2: 325-332.

Landis, A., N. Lapointe, P. Angermeier. 2011. Individual growth and reproductive behavior in a newly established population of northern snakehead (Channa argus), Potomac River, USA. Hydrobiologia, 661: 123-131.

Lapointe, N., J. Odenkirk, P. Angermeier. 2013. Seasonal movement, dispersal, and home range of northern snakehead Channa argus (Actinopterygii, Perciformes) in the Potomac River catchment. Hydrobiologia, 709: 73-87.

Lapointe, N., J. Thorson, P. Angermeier. 2010. Seasonal meso- and microhabitat selection by the northern snakehead (Channa argus) in the Potomac River system. Ecology of Freshwater Fish, 19: 566-577.

Nguyen, T., Y. Li, P. Makouloutou, L. Jimenez, H. Sato. 2012. Posthodiplostomum sp. metacercariae in the trunk muscle of northern snakeheads (Channa argus) from the Fushinogawa River, Yamaguchi, Japan. Journal of Veterinary Medical Science, 74/10: 1367-1372.

Odenkirk, J., C. Lim, S. Owens, M. Isel. 2013. Insight into age and growth of northern snakehead in the Potomac River. North American Journal of Fisheries Management, 33: 773-776.

Orrell, T., L. Weigt. 2005. The northern snakehead Channa argus (Anabantomorpha: Channidae), a non-indigenous fish species in the Potomac River, U.S.A. Proceedings of the Biological Society of Washington, 118/2: 407-415.

Poulos, H., B. Chernoff, P. Fuller, D. Butman. 2012. Ensemble forecasting of potential habitat for three invasive fishes. Aquatic Invasions, 7: 59-72.

Saylor, R., N. Lapointe, P. Angermeier. 2012. Diet of non-native northern snakehead (Channa argus) compared to three co-occurring predators in the lower Potomac River, USA. Ecology of Freshwater Fish, 21: 443-452.

Wang, J., G. Yang. 2011. The complete mitogenome of the snakehead Channa argus (Perciformes: Channoidei): Genome characterization and phylogenetic implications. Mitochondrial DNA, 22/4: 120-129.

Wang, Q., W. Wang, Q. Huang, Y. Zhang, Y. Luo. 2012. Effect of meal size on the specific dynamic action of the juvenile snakehead (Channa argus). Comparative Biochemistry and Physiology, Part A, 161: 401-405.