Channoidei

(Snakeheads)

Class Actinopterygii

Order Perciformes

Suborder Channoidei

Number of families 1

Evolution and systematics

The single-family (Channidae) suborder Channoidei (snakeheads) is composed of only two genera, Channa, which includes all Asian species, and Parachanna, which includes all African species. The two genera differ mainly in the morphology of the air-breathing (suprabranchial) organ; that of the latter being less developed. Currently, 25 species of Channa and three species of Parachanna have been recognized. Although snakeheads have been considered a sister group of the Anabantoidei (climbing gouramies) or the Synbranchiformes (swamp eels), the relationship of snakeheads to other fish groups still remains uncertain. The earliest fossil record of snakeheads is Eochanna chorlakkiensis from the Kuldana Formation, Pakistan (middle Eocene).

Physical characteristics

Snakeheads form a morphologically unique group of primarily freshwater fishes, which greatly vary in size at maturity. Some species have distinctively small pelvic fins, while a few others lack them completely. Generally, snakeheads have an elongated cylindrical body; flattened head; long, entirely soft-rayed dorsal and anal fins; a large mouth with well-developed teeth on both upper and lower jaws; tubelike anterior nostrils; a round to somewhat truncate caudal fin; cycloid or ctenoid body scales; shield-like scales on a head that superficially resemble that of a snake; a lengthy, elongated swim bladder reaching to the caudal peduncle region; and an accessory air-breathing apparatus (suprabranchial organ) in the head region. This suprabranchial organ is mainly composed of three parts: a suprabranchial chamber, epibranchial respiratory fold, and hyomandibular process.

Species of snakeheads can be distinguished based on coloration, meristics, and morphometrics, as well as the distribution of scales on the underside of the lower jaw, the shape of the head, and the morphology of the suprabranchial organs. Much taxonomic confusion has resulted from the fact that coloration in each species changes dramatically during growth, and in many cases, the color of juveniles is completely different from that of adults. One such case is the giant snakehead (Channa micropeltes), a popular aquarium fish that has striking black and red "racing stripes" as a juvenile, but variegated blackish markings as an adult. Many species have distinct adult coloration, such as ocellus (ocelli) on the body and/or caudal fin, vertical bands on the pectoral fins, and small spots on the body.

Distribution

Members of the genus Channa are widely distributed, occurring from Iran in the west, to China and southeastern Russia in the east, and throughout Southeast Asia, extending downward into the Philippines and Indonesia (Java being the southernmost location). Species of the genus Parachanna are restricted to central West Africa. Species are most diverse in tropical Asia. Some species are endemic to restricted areas that include special features such as tropical rainforests, such

as the walking snakehead (Channa orientalis) from southern Sri Lanka, and the orange-spotted snakehead (Channa aurantimaculata) and rainbow snakehead (Channa bleheri) from northern Assam. Some species are now found outside their natural distributions, apparently as a result of human introduction. These include established populations of the northern snakehead (Channa argus) in Japan, the United States, and Aral Sea basin; the blotched snakehead (Channa maculata) in Japan; the bullseye snakehead (Channa marulius) in the United States; and the striped snakehead (Channa striata) in the islands of Indonesia east of Wallace's line, Papua New Guinea, New Caledonia, Fiji, Hawaii, Mauritius, and Madagascar. In Madagascar the striped snakehead has had a severely detrimental effect upon the island's endemic freshwater fish fauna.

Habitat

Most snakeheads prefer stagnant or slow-running waters, usually hiding under vegetation, rocks, and sunken trees. However, large species such as the northern snakehead, bullseye snakehead, and giant snakehead can usually be found inhabiting relatively deep waters with somewhat heavy vegetation in low, open country such as large rivers, swamps, ponds, and reservoirs. One species, the banka snakehead (Channa bankanensis), has been found only in peat swamps, which have dark brown, highly acid water. Most small species, such as the walking snakehead, usually live in mountain streams, but can also be found in lowland habitats. The northeastern Indian barca snakehead (Channa barca), a large species attaining 35.4 in (90 cm), is reported to live in holes within the banks of ponds and rivers. Many snakeheads are highly adaptable, being tolerant to a wide range of environments, including polluted waters.

Behavior

Highly territorial, snakeheads usually stay hidden, and migrate only short distances. Fry of some species have been reported to be cannibalistic, opportunistically eating eggs from a later spawn. Generally, the young tend to school. Snakeheads appear to need to breach the water surface periodically to exchange the air in their suprabranchial chamber. Experiments have shown that breathing surface air is far more important to them than using their gills. This is supported by evidence from the drowning deaths of fishes that have been caught in nets under water, and could not surface to breathe. Some species of snakeheads can live out of water for several days if their bodies are wet, amazingly migrating on land during the raining season by using their bodies, pectoral fins, and caudal fins. However, no one has reported them feeding while moving on land. The striped snakehead (Channa striata) has been reported to survive in the bottom mud of lakes, swamps, and canals that have dried up; fishermen using long knives to cut away the mud in layers have found these fishes singly or in clusters within cavities of the mud.

Feeding ecology and diet

Active during the day, although the dwarf snakehead (Channa gachua) has been reported to be nocturnal, all snakeheads are predatory, ambush feeders, eating almost any animal smaller than their mouths. Usually solitary feeders as adults, as juveniles they actively migrate in schools, hunting foods such as zooplankton, small insects, and crustaceans. Adult snakeheads feed on everything from insects (both terrestrial and aquatic) to young birds, including fishes, frogs, tadpoles, lizards, geckos, mice, rats, and ducks. They primarily

hunt by sight, but smell and other senses may also be involved. They sometimes jump up from the water surface to grasp their prey.

Reproductive biology

Although the reproductive biology of many species of snakeheads is still unknown, it does appear that they are monogamous, exhibit parental care, and become aggressive, especially so during breeding. Many are known to be nest breeders, the parents first clearing vegetation and then building a simple circular nest at the water surface. In these species, there is a spawning embrace with the male encircling the female, squeezing the eggs out, and fertilizing them. The eggs float upward into the nest, usually guarded. After hatching, the fry will be cared for by either parent, dependent on species. The giant snakehead, with its strong canine-like teeth, has been known to attack and seriously injure humans who disturb it, especially while guarding its brood. On the other hand, two small species, the walking and dwarf snakeheads, are known to be mouth brooders, with the male reported to keep the fertilized eggs, and later fry (for a few days), in his mouth.

Conservation status

Although generally not threatened, the status of populations of some species are poorly known. No species are included on the IUCN Red List.

Significance to humans

Most channid species are important food fishes in southern Asia and China and the flesh is considered delicious. Some medium-to-large species are cultured in ponds or in cages set in slow-running rivers. Although sold fresh and sun-dried, several species, northern snakehead (C. argus) and striped snakehead (C. striata), are known as intermediate hosts of parasites harmful to humans, including Gnathostoma (jaw worms), and should be cooked thoroughly at a high temperature before eating. Two species have even been used as predators to control tilapia in aquaculture ponds. Larger species are popular game fishes in Asia, and several species feature in local beliefs or myths. In October 2002, the U.S. Fish and Wildlife Service passed a rule that prohibits the importation of live snakeheads into the United States except by scientific, medical, or educational organizations, which would be required to obtain a permit to import the fishes.

Species accounts

List of Species

Northern snakehead

Channa argus

family

Channidae

taxonomy

Ophicephalus argus Cantor, 1842, Chusan Island, China.

other common names

German: Amur-Schlangenkopf; Chinese: Hey yu; Japanese: Kamuruchi; Russian: Zmeegolov.

physical characteristics

Length 44.1 in (112 cm); a large snakehead. Has relatively small scales (LL=61–72), no scales on the underside of the jaw, large canine-like teeth on the upper and lower jaws; two horizontal rows of 9–15 irregular dark brown blotches that sometimes coalesce, and brownish pectoral fins with a black mark at the base.

distribution

Central China (Yangtze to Luan River basins) including Korea to the Amur River basin, southern Russia; introduced and established in Japan, the United States, and republics in the former Soviet Union adjacent to Caspian Sea.

habitat

Lakes, swamps, marshes, reservoirs, and rivers in lowland slow-moving to stagnant temperate waters.

behavior

Known to burrow into the mud and hibernate when the water becomes very cold, has not been reported to move over land.

feeding ecology and diet

Feeds on fishes, frogs, prawns, worms, crayfishes, and juvenile water birds.

reproductive biology

Spawns usually in early morning from spring to summer, Male and female build donut-shaped nest about 39.4 in (100 cm) in diameter using aquatic plant debris. Female deposits an average of 7,300 eggs 0.06–0.08 in (0.15–0.2 cm) in diameter; incubation takes about 45 hours at 77°F (25°C). Guarded and cared for by the parents, newly hatched fry are all black, and leave the nest when they reach 0.03 in (0.8 cm), at which size the body has become yellowish.

conservation status

Not threatened; common in almost all areas within its distribution.

significance to humans

One of the most popular food fishes in China, where it is believed to be beneficial for helping in postpartum recovery.

Orange-spotted snakehead

Channa aurantimaculata

family

Channidae

taxonomy

Channa aurantimaculata Musikasinthorn, 2000, Dibrugarh, Assam, India.

other common names

Assamese: Naga cheng.

physical characteristics

Maximum length 19.7 in (50 cm). Has two large scales on each side of lower jaw undersurface, scales relatively large (LL=51–54), black spot at the base of the pectoral fins with five vivid black vertical broad bands, and relatively small pelvic fins (less than half of pectoral fins). Very colorful, upper half of body dark brown to black, with seven or eight large irregular orange blotches, becoming yellow, golden, or orange below, and changing to blue ventrally, with many scattered small black spots.

distribution

Known only from Dibrugarh (Brahmaputra River basin), Northern Assam, India.

habitat

Streams, swamps, and ponds probably throughout the region's discontinuous patches of tropical rainforest.

behavior

Effectively transverses wet terrestrial environments.

feeding ecology and diet

Nothing known.

reproductive biology

Nothing known.

conservation status

Not listed by the IUCN.

significance to humans

Sold in local markets as food fish; also known as an aquarium fish.

Rainbow snakehead

Channa bleheri

family

Channidae

taxonomy

Channa bleheri Vierke, 1991, upper portion of Dibru River, near Guijan, Brahmaputra River basin, northeastern Assam, India.

other common names

Assamese: Deo cheng.

physical characteristics

Length 3.9 in (10 cm), one of the smallest snakeheads. Has relatively large scales (LL=42–46), no pelvic fins, and a single large scale on each side of the underside of the lower jaw. One of the most colorful snakeheads, has very distinctive 4–11 medium-to-large irregular red or orange spots on the caudal fin which sometimes coalesce; and pectoral fins with a black spot at the base and 7–9 black concentric bands.

distribution

Endemic to Brahmaputra River basin, northern Assam, India.

habitat

Forest streams, swamps, and ponds connected with the Brahmaputra River.

behavior

Highly capable of terrestrial movement.

feeding ecology and diet

Nothing known, but is probably a predator feeding on insects, crustaceans, and small fishes.

reproductive biology

The species guards the eggs, which float at the water surface.

conservation status

Not threatened, but because of its relatively small, highly restricted distribution, along with its popularity among aquarists, there is a possibility that over-collecting of natural populations may cause a serious decline in the future.

significance to humans

Due to some spiritual reasons, not considered a food fish by the local Assam populace (the Assamese common name means "ghost [or spirit] snakehead"); a popular aquarium fish.

Bullseye snakehead

Channa marulius

family

Channidae

taxonomy

Ophiocephalus marulius Hamilton, 1822, ponds and freshwater rivers of Bengal.

other common names

English: Great snakehead; Thai: Pla chon ngu hao, pla kalon; Burmese: Nga yan dyne; Laotian: Pa gooan; Khmer: Trey raws; Bengali (West Bengal): Sal, gajal; Sinhalese: Ara.

physical characteristics

Among the largest of snakeheads (48 in or 122 cm maximum length). It has 4–6 large round black blotches on the body; some populations have white margins and small white spots on these blotches. Also has a white or orange-rimmed ocellus on the upper portion of the caudal fin base (sometimes absent or indistinct in indiviuals over 300 mm SL), moderately large scales (LL=52–70), and no scales on the underside of the lower jaw. Also, young may have an orange longitudinal band running from the tip of the head to the caudal fin that fades as the fish matures.

distribution

Widely distributed in tropical Asia from the Indus River basin of Pakistan and the whole Indian subcontinent, including Sri Lanka, through Myanmar and Indochina. Also introduced and established in Florida, United States.

habitat

Large rivers, lakes, and reservoirs; prefers clear stretches of water with a sandy and rocky bottom.

feeding ecology and diet

Known to feed mainly on fishes. It probably also eats other vertebrates and invertebrates such as frogs and crustaceans.

behavior

The species is capable of terrestrial movement.

reproductive biology

In West Bengal this species spawns from April to June. Parents use their mouths to cut elaborate passages through the weeds leading to the floating bubble nest, where 2,000–40,000 light red-yellow eggs (0.08 in [2 mm] in diameter) hatch in about 54 hours. The pair also guards the fry.

conservation status

Not threatened.

significance to humans

Readily seen as a food fish in India and some parts of Southeast Asia. A number of interesting local beliefs are attributed to this fish. In central Thailand, the common name means "cobra snakehead" and comes from the superstition that its bite is very poisonous, leading to death. In Myanmar, the Karen people regard it with awe and avoid eating it, practices that arise out the belief that these fish were formerly humans who were changed into fish for their sins, as well as the belief that if a person eats one, he or she will be transformed into a lion.

Giant snakehead

Channa micropeltes

family

Channidae

taxonomy

Ophicephalus micropeltes Cuvier in Cuvier and Valenciennes, 1831, Java.

other common names

English: Red snakehead; Khmer: Trey chhdaur; Laotian: Pa do; Malay: Ikan toman: Thai: Pla chado; Vietnamese: Cá bong.

physical characteristics

Length 51.2 in (130 cm); one of the largest snakeheads. Has very small scales (LL=83–106); patch of small scales near underside tip of lower jaw; large canine-like teeth on upper and lower jaws. Juveniles have vivid black horizontal stripe above and below a bright orange to red stripe running head to tail. Coloration fades into bluish black and white dappled upper body in adults.

distribution

Widely distributed in Southeast Asia (excluding Myanmar and northern Vietnam) and coastal region of southwestern India.

habitat

Large, slow-running to stagnant waters in open country.

behavior

The most aggressive snakehead; has not been reported to travel over land.

feeding ecology and diet

Extremely voracious, consumes fishes of all kinds and sizes, frogs, and even juvenile ducks and water birds, killing far in excess of need. Young or subadults tend to school when hunting for smaller fishes.

reproductive biology

Male and female build donut-shaped floating nest from surrounding aquatic vegetation into which the floating eggs are placed. Parents aggressively guard and care for eggs and fry. Once fry hatch, they soon form and forage as a dense school.

conservation status

Relatively to very common in Southeast Asian range; status of population in southwestern India is unknown.

significance to humans

One of the most popularly marketed snakehead fishes in Southeast Asia. Adults are primarily game fish, juveniles are recognized worldwide as aquarium fish.

Walking snakehead

Channa orientalis

family

Channidae

taxonomy

Channa orientalis Bloch and Schneider, 1801, India "orientali" (presumably Sri Lanka).

other common names

English: Smooth-breasted snakehead; Sinhalese: Kola kanaya.

physical characteristics

Maximum length 3.9 in (10 cm); one of the smallest snakeheads. Pelvic fins absent; body scales relatively large (LL=39–43), and a single large scale is on each side of the underside of lower jaw. Body often has bluish cast with 8–11 black descending bands on a grayish to dark brown dorsal background blending into a whitish ventral, with an orange to red outer margin on the dorsal, anal and caudal fins, a black spot at the base with 3–8 concentric black bands on the pectoral fins. Single orange or yellow-rimmed black ocellus at the back end of the dorsal fin in young usually fades away by maturity.

distribution

Endemic to tropical rainforest environment of southern Sri Lanka.

habitat

Small, shallow rivulets barely deeper than its body, and also in mountain streams, small ponds, and ditches.

behavior

Known to effectively transverse land.

feeding ecology and diet

Feeds mostly on terrestrial and aquatic insects, caddisflies, and small fish.

reproductive biology

Mouth brooders. Around 40 eggs are deposited in the floating nest, then 9–10 days after fertilization the male takes the eggs into his mouth for hatching. After hatching, either parent may hold the brood, which exits and enters through the gills, not the mouth. Fry feed on eggs laid later by their mother.

conservation status

Not threatened, but a decline in the number of unpolluted streams and shrinking rainforests in Sri Lanka will probably affect future populations in the future.

significance to humans

A small number have been exported for the aquarium fish trade.

Ocellated snakehead

Channa pleurophthalmus

family

Channidae

taxonomy

Ophicephalus pleurophthalmus Bleeker, 1851, Bandjermassing.

other common names

Indonesian: Kerandang.

physical characteristics

Total length 15.7 in (40 cm). Body is distinctively compressed laterally and quite deep compared to other snakeheads, has moderately large scales (LL=49–55), large canine-like teeth on the upper and lower jaw, and patch of small scales near the tip of the underside of the lower jaw. Body grayish with scattered small black spots and several orange or orangey red-rimmed black ocelli, yellowish black to gray pectoral fins, and a single ocellus on the gill cover and middle of the caudal fin.

distribution

Islands of Sumatra and Borneo (western and southern portions), Indonesia.

habitat

Usually lowland, slow-moving murky rivers.

behavior

Not known to be capable of terrestrial movement.

feeding ecology and diet

Nothing known; presumed to be a predator, feeding on fishes and other small aquatic animals.

reproductive biology

Nothing known, but like other medium-to-large snakeheads, is probably a bubble nest builder.

conservation status

Not threatened.

significance to humans

Marketed as a food fish within its distribution, also quite popular as an aquarium fish.

Striped snakehead

Channa striata

family

Channidae

taxonomy

Ophicephalus striatus Bloch, 1793, Tranquebar, Malabar coast, India.

other common names

English: Chevron snakehead, snakehead murrel; German: Quergestreifter Schlangenkopf; Burmese: Nga-yan; Khmer: Trey raws; Bengali: Shol; Laotian: Pa kho; Malay: Aruan; Indonesian: Ikan gabus; Thai: Pla chon; Vietnamese: Cá lòk.

physical characteristics

Length 23.6 in (60 cm). No scales on underside of the jaw, no large canine-like teeth on the upper jaw, moderately large scales (lateral line scales 50–61). Generally dark brown above, extending into irregular blackish bands below; no bands or spots on pectoral fins. Juveniles have black spot (sometimes forming an ocellus) at posterior end of dorsal fin, but this disappears as fish reaches maturity.

distribution

The most widely naturally distributed snakehead, occurs from Pakistan through Southeast Asia east to Yunnan, southern China. Has also been introduced and established in tropical islands, including Madagascar, Hawaii, New Guinea, the Philippines, and Sulawesi, Indonesia.

habitat

Tropical stagnant to slow-running lowland waters (prefers the former) with muddy bottoms, such as ponds, swamps, and ditches.

behavior

Can move over land during rainy season. Reported to survive in cavities in the bottom mud of lakes, swamps, and canals that have dried up.

feeding ecology and diet

In native waters, feeds on smaller fishes, frogs, prawns, and worms.

reproductive biology

Spawns year round, builds a nest in shallow (11.8–39.4 in/30–100 cm), swampy stagnant areas near waters' edge. Male and female use mouth and tail to clear away dense vegetation to make donut-shaped floating nest about 11.8 in (30 cm) in diameter, into which the translucent yellow nonadhesive eggs (about 0.06 in/0.15 cm in diameter) are placed. Hatching period lasts about three days, during which male guards the nest until a short while after the vivid reddish orange fry hatch. After hatching, fry move in a dense school while foraging, still protected by male.

conservation status

Not threatened; common in almost all areas within its distribution.

significance to humans

One of the most common and important freshwater food fishes in tropical Asia, also used for control of tilapia in pond aquaculture. In Myanmar, included in a spiritual ceremony to help a sick person recover.

African snakehead

Parachanna obscura

family

Channidae

taxonomy

Ophiocephalus obscurus Günther, 1861, West Africa.

other common names

German: Dunkelbäuchiger Schlangenkopf; Dinka: Abioth; Ga: Hauti; Hausa: Tuhi.

physical characteristics

Length 15.7 in (40 cm). Medium-sized, head somewhat concave, pointed in lateral view and depressed anteriorly; has small scales (LL=65–78), patch of small scales near the tip of the underside of the lower jaw, and no large canine-like teeth on the upper jaw. Body brown to dark brown with several large black blotches, blackish mark at base of pectoral fins along with several rows of black spots. Young have broad blackish band on body sides and light-edged ocellar spot at the caudal fin base.

distribution

The White Nile and from the Senegal and Chad Rivers to the Congo River basin in western Africa; most widely distributed African species.

habitat

Slow-running to stagnant waters, preferably with heavy vegetation, including rivers, streams, lakes, lagoons, and marshes.

behavior

Adults are solitary ambush predators. Overland movement of this species has never been reported.

feeding ecology and diet

Juveniles feed on prawns, copepods, and aquatic insect larvae; adults prefer mostly fishes.

reproductive biology

Female lays 2,000–3,000 eggs in October and November which are probably deposited in a nest and guarded by the male for 4–5 days after hatching.

conservation status

Not threatened.

significance to humans

Of minor importance as a food fish within its distribution, cultured in ponds and also used to control tilapia in aquaculture.

Resources

Books

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Periodicals

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——. "Breeding the Green Snakehead: It's a Mouthbrooder!" Tropical Fish Hobbyist 37, no. 10 (1989): 34–36.

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——. "Channa panaw, a New Channid Fish from the Irrawaddy and Sittangriver Basins, Myanmar." Ichthyological Research 45, no. 4 (1998): 355–362.

Musikasinthorn, P., and Y. Taki. "Channa siamensis (Günther, 1861), a Junior Synonym of Channa lucius (Cuvier in Cuvier and Valenciennes, 1831)." Ichthyological Research 48, no. 3(2001): 319–324.

Roberts, T. R. "The Freshwater Fishes of Western Borneo (Kalimantan Barat, Indonesia)." Memoirs of the California Academy of Science 14 (1989): 1–210.

Roe, J. L. "Phylogenetic and Ecological Significance of Channidae (Osteichthyes, Teleostei) from the Early Eocene Kuldana Formation of Kohat, Pakistan." Contributions from the Museum of Paleontology 28, no. 5 (1991): 93–100.

Smith, H. M. "The Freshwater Fishes of Siam or Thailand." Bulletin of the U.S. National Museum 188 (1945): 1–622.

Victor, R., and B. O. Akpocha. "The Biology of Snakehead, Channa obscura (Gunther), in a Nigerian Pond Under Monoculture." Aquaculture 101 (1992): 17–24.

Vierke, J. "Ein farbenfroher neuer Schlangenkopffisch aus Assam Channa bleheri spec. nov." Das Aquarium 259 (1991): 20–24.

Zhang, C. -G., P. Musikasinthorn, and K. Watanabe. "Channa nox, a New Channid Fish Lacking a Pelvic Fin from Guangxi, China." Ichthyological Research 49, no. 2 (2002): 140–146.

Prachya Musikasinthorn, PhD