Channa in general
Channa, commonly known as Snakeheads, are primitive predatory fish and members of the family Channidae. They are a group of perciform (perch-like) fishes whose affinities are unknown, although recent studies on the molecular phylogeny of bony fishes consider snakeheads as most closely related to the labyrinth fishes (anabantoids) and the synbranchiform eels, which include the spiny eels.
The genus Channa contains 31 species that are native thoughout Asia from are native from
southeastern Iran and eastern Afghanistan eastward through Pakistan, India, southern
Nepal, Bangladesh, Myanmar, Thailand, Laos, Malaysia, Sumatra, Indonesia,
Vietnam, Korea, and China northward into Siberia.
3 species of the closely related genera Parachanna are native to parts of Africa.
The different species of Channa vary in size considerably. The term dwarf snakeheads is coined by aquarists to describe a group of Channa species growing only 25 centimeters: Channa bleheri, Channa cachua, Channa orientalis and Channa andrao. These species are most suitable for keeping in an aquarium because of their size and their relative docile temperament.
Most of the species grow to a maximum length of 30-90 centimeters. Besides size, this intermediate category contains the most diversity in behaviour since some of the species are closer related to the dwarf species, and some relate more to the category of monsterfish.
5 species (A. argus. C. barca, C. marulius, C. micropeltes and C. striata) can even grow up to 100 cm or even larger and can be considered monsterfish that are barely suitable for aquaria.
Fossiles dated from 50 million years ago indicate an origin in the southern Himalayas (India and East Pakistan). From 15 million years ago end on, the animals have spread by the expanding intertropical climate zone to parts of Europe, Africa and larger parts of Asia.
Channa have an elongated body and are distinguished by their long dorsal fins large mouths full of teeth. They earn their common name Snakehead because their flattened shape and the scales on their heads that are reminiscent of the large epidermal scales on snakes.
Channa have gills to breath water like most other fish. However subadults and adults can also breath air to supplement their demand for oxygen. Snakeheads are in fact obligatory air breathers and must have air from the surface otherwise they will drown. Unlike many other airbreathing fishes, channa have a series of cavities in the rear section of their head. These suprabranchial chambers are filled with folded tissues that have a high surface area, and allow oxygen change to occur directly between air and their blood. Unlike mammals they lack a diaphragm, and use water to exchange old air with fresh air each time they take a breath. Thus, their ability to breathe air when out of the water is limited. They appear to breathe air more frequently when swimming actively.
The genera Parachanna (native to parts of Africa) is described apart from the genera Channa because of a more primitive implementation of the airbreathing section.
Snakeheads are known to migrate over short distances over land to find other waterbassins, using the ability to breath air. When moving over land they curve their body in an S shape first, before launching themselves forward by a powerful stretch. In high humidity conditions Channa are able to survive from 2 up to 4 days out of the water. When placed in direct sunlight, however, they dessicate and perish in minutes to several hours. In contrary to what is believed, Snakeheads are not known to leave the water for any reason other than making their way back to water after flooding. The only true Snakeheads to actively leave the water are some of the smaller species, C. gachau and C. orientalis, C. asiatica, and C. amphibeus, and still there must be an obvious reason for change.
Snakeheads are able to live in varying waterconditions. Some species are bound to a subtropical climatezone. For good health these species require cooler watertemperatures., at least for a seasonal period. Most snakeheads can tolerate a very large range of waterparameters (temperature, PH, GH, level oxygen). However, they are very vulnerable in case of sudden changes.
Snakeheads are highly valued as foodfish, particularly in India, southeastern Asia, China, and to a lesser extent in Africa. They have long been an important part of capture fisheries and, in recent decades, some species (C. maculata, P. obscura, C. striata, C. argus) have been utilized in aquaculture and a few used as predators to control density of tilapiine fishes that are considered pestfishes in agricultural installations. Often local markets are stocked anyday of the year with large amounts of Snakeheads. Sellers make use of the ability of the fish to survive for a long time in just a thin film of water. As a result fresh fish can be offered anytime of the day, which offers some benefits in a long hot day at a local market. Due to colonisation, in the last 100 years Channa species have been introduced in many countries (Madagascar, Hawaii, Taiwan, Japan, Kazachstan, Turkmenistan, Uzbekistan and the Czech Republic).
It is reported that some Channa species possess anti-inflammatory properties. They are also known to have certain PUFAs that can regulate prostaglandin synthesis and also induce wound healing. The fish oil can have positive effects on cardiovascular diseases and cancers.
“Fish out of hell”
Currently, in absence of natural toppredators the larger channa species are considered invasive and destructive to the local ecosystem. Larger species become sexually mature after 2 to 3 years (15-30 cm) already, can mate up to 2-5 times a year, and can produce up to 15.000 eggs at once. Especially C. Argus is considered to have the ability to double its population within 15 months, and be able to flourish in most (fresh) waterconditions.
Discovery of several large Channa species in waterbassins in the US made big news. The media had been set up to legitimate unpopulair activities preventing the species from spreading to other watersystems (like emptying or poisoning waterbassins). Several media painted a picture of Piranha like myths about monsterfish that empty a lake, move on to the next to empty, hunting on dogs and children in the meantime on land. National Geographic launched a somewhat more fact based documentairy, Invasion of the Snakeheads, introducing the name “Fishzilla”. Last but not least, Hollywood filmmakers found inspiration and support to dedicate 2 horrormovies to the monsterfish.
Asian foodmarkets (and the related stocking of fish in natural fishbassins) have been reported as the rootcause of the invasion of Channa in the US. Also, this make the fish quickly available to aquarists. Specimens that outgrew the fishtank often ended up in the local ecosystem. Since 2002 in most states of the US it is forbidden to possess living Channa species.
Channa are predatory fish that prey in the juvenile stadium on plankton, insects and snails. While they grow the larger species switch towards a menu that consists mainly on fish, frogs, crabs, shrimps, small aquatic mammals and birds.
Before adulthood most Channa species hunt in groups. When becoming sexually mature they start a solitary life and develop a high level of aggression against their own species and other fish. When a couple has formed most species do not tolerate other fish.
Channa are not active swimmers and, when not feeding, tend to move only when surfacing for air. They spend a lot of time hovering in midwater or resting on the bottom within cover as ambush predators. Some larges snakeheads however live a more pelagic life and are far more active swimmers. All snakeheads are capable of powerful bursts of acceleration. They curve their body in a S-shape and launch themselves forward by stretching.
Parental care is behavioural characteristic of Snakeheads. Both parents protect and guard their young vigorously. The majority of the species guard their eggs at the surface of the water. Some of the smaller species are mouthbrooder. Only some species are holebrooders.
Amongst specialist aquarists Channa is a popular -oddball- aquariumfish. Snakeheads are elegant, alert, clever, restful and powerful fish, with lots of personality. Their communication with conspecifics their hunting skills and breeding behaviour are fascinating. Some aquarist even specialize themselves by dedicating their large fishtank to the largest specimens. Sometimes they maintain a pet-like connection with their monsterfish. Some rare and attractively marked species (like C. Barca) belong to the most expensive aquariumfish in the trade.
Some Snakeheads display considerable changes in colour pattern while growing. In the early days of classification of fishspecies this formed a lot confusion since in that days colour was still considered a criterium for classication.
Besides some dwarf species, many juveniles are more attractively marked than adults. With age species often develop a browner, more drab look. Because of this phenomen some aquarists lose interest in the fish while it grows. Those considering their first purchase should be well aware of what they are getting into.
Because of its predatory nature none of the Snakeheads are a suitable choice for a community tank. Most of the species will quickly empty a general communitytank with smaller fish. Thus a dedicated aquarium is required for keeping snakeheads.
Aquarists have very diverse experiences when it comes to combining Channa species with other robust fish species. In general, most species are probably best kept alone. The level of tolerance towards other fish varies per species, but also seem to vary per specimen or specific situation. Combining Channa with other aggressive and territorial fish species, like members of the Cichlidae family is a strategy that does not work out well. A Channa that is intimidated will hide, try to escape the tank and refuse to eat.
Because of their size and relatively mild temperament most of the dwarf species can be combined with fish from 2/3 of their own length, as long their tank mates are not overly aggressive. Keep in mind that most of the members of the dwarf species are native to areas with varying water conditions, depending on the season. A seasonal drop of water temperature is required too maintain good health.
Medium sizes species
Many medium sized channa (30-60 cm) should be combined with relatively fast swimming and robust fish, like larger cyprinids. The general opinion is that changes are best if the Snakeheads are not fully grown and the other fish are already settled. Newly introduced fish are often killed, even when they do not fit their mouth. Mostly however, the co-existence is temporarely: When a couple is formed often all other fish are hunted and killed.
Large species (60 – 130 cm)
These species require a lot of space. Most private aquarium setup’s are just large enough to host only 1 or 2 adults. Young species often can tolerate conspecifics ans other robust fish very well. Newly introduced fish are often ripped apart instantly. Adultfish (especially formed couples) develop the maximum level of aggression. Most of the time they are the last fish standing in an aquarium set-up.
Channa argus – Northern Snakehead
Channa Argus is a large snakehead species. It is easy distinguished by the Python-like colourpattern. Channa argus has large scales at the side of the head, a feature where the name Snakehead comes from. Most specimen grow 80-90 cm. In Russia specimens of 150 cm (weight 8 kg) are reported. However these are unconfirmed observations.
Channa argus is native to China, zuidelijk en zuidwestelijk van de Yangtze en Korea. More specific the lower Amur river, Ussuri river, including lake Khanka, Sungari river, Tunushka river, and most of Korea (except the north-east).
Channa argus is an important foodfish and is cultivated intensively in native and in foreign countries. In the past this species is also introduced in many countries.
Channa argus consists of 2 subspecies:
- Channa Agus argus: China en Korea population
- Channa Argus warpachowskii: East Russia population
Channa argus prefers shallow (<3 meter) water, but is able to flourish in almost all watertypes, except brakish water. Fast streaming water is avoided.
Channa argus, with 3 other Snakehead species) has given Snakeheads a bad reputation. As a result of local foodmarkets and breeding activities these snakeheads have been able to establish themself in local eco-systems. Especially Channa argus is considered extremely invasive and highly destructive to the local ecosystem:
- Channa prefers low temperatures and can stand temperatures within a range of 0 to 20 degrees C. With this ability they can survive in almost every climatezone
- Fast reproduction
Channa argus becomes sexually mature after 2-3 years (15-30 cm), mate up to 5 times a year and can produce up top 15.000 eggs at once. It is believed the species can double its population within 15 months
- Mature specimens are believed to kill more fish than they can eat. As a toppredator it lacks natural predators like human
- Their ability to migrate over land
Like other Snakeheads Channa argus has the ability to migrate short distances over land to other watersystems. In case of Channa argus this ability only youngsters have this ability. Other then most Snakeheads older speciment develop a round belly and lose te ability to move over land.
After 3 species of Snakeheads were found throughout the USA In most US states it is prohibited to posess a living Snakehead. The release of the fish in the US supposedly occured since the species was popular on local Asian foodmarkets. It was bred intensively and often livestock was kept in ponds. With its availability as a foodfish it became quickly available to aquarists too. Specimens that outgrew aquaria often ended up in nature. After the species had been discovered by serveral fisherman a red alert was put on leading to a lot of media exposure. National Geographic launched the documentaire Invasion of the Snakeheads and introduced the name ‘Fishzilla’. Several watersystems had been cleared of poisoned by regional government to prevent the fish from spreading to the large lakes. The media produced Piranha-like myths about monsterfish that empty a lake and then simply walk to the next lake , hunting on children and dogs on land while on their way. Hollywood make 2 horrormovies out of this.
However, the threat to the local ecosystem is to beconsidered serious and requires continue attention. This map shows the actual distribution of Channa argus within the US. Also within EU counties import restrictions on this species are in place.
Because of the size, growth rate, and the amount of food needed, this monsterfish is only suitable for an aquarium of the size of a public installation. Channa argus is a powerful fish with an quite explosive character. It is said that the fish is able to jump up 4 meters high out of the water, so it is advisable to use a tight fitting cover.
Young specimens combine reasonably well with other fish of similar same size (or are very small!), under the condition that they grow up with them. When sexually mature Channa argus becomes intolerant and aggressive. From 60 cm and onwards feeding and maintenance of the aquarium can become quite dangerous, since all movement around or above the aquarium will be considered food.
If someone is in to these species, Channa maculata is a better choice for the larger aquarium, since it has similar appearance but grows considerably smaller.
Channa are fantastic escape artists. With their muscled body they can squeeze themselves though every gap and even lift the cover. A tight fitting cover is a must.
Channa must breath air otherwise they drown, which requires an airgap between the waterlevel and the cover of the tank
Carnivorous. All livefood will be eaten. Often the fish will accept frozen food, chunks of fish and even sinking meaty pellets. Don’t feed the fish beef or chicken meat. Some of the lipids from these meat source cannot be properly metabolised by the fish and may cause excess fat deposits and even organ degeneration.
Grown fish should be fed using forceps to prevent injury – to the human.
Af far as known breeding has not occur in aquaria. Channa argus however has been cultivated intensively. Breeding requires a lot space and leaves the breeder with a lot of juvenile fish that are not valuable. TThe fish are sexually mature after 2 years. When snakeheads mate, they are usually monogamous for an entire breeding season, and perhaps throughout their lifetimes.
The eggs are laid in substrate and rise to the surface. The parents offer an intensive and enduring care for the juveniles. When the offsping is freeswimming, the parents will guide them through the water, in a way that is comparable to ducks and their fledgelings.
Possible intruders must face strong aggression from the parents who are guarding fry. Parent snakeheads guard their young vigorously. Even swimming people can be hurt badly. It will almost become impossible to carry out maintenance activities in the tank.
Patrick de Pijper