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 last fish standing in an aquarium set-up.
Channa marulius is widespread throughout Asia. The range of distribution is from Pakistan, India, Bangladesh, Nepal, Myanmar, Thailand to Southern China, Laos and Vietnam. General opinion is that the range of distribution might be even larger and that Channa Muriulius should be considered a complex of species instead of a species.
Channa marulius inhabits larger rivers, inland lakes, canals and swamps and prefers watertypes with dense vegetation. Channa Marulius is one of the Snakehead species with a pelagic lifestyle. Most speciments grow 50-60 cm. Confirmed observations of larger specimens (up to 120-180 cm) are known, which makes Channa murulius the largest Snakehead. A population Channa marulius inhabits Florida, where it is considered a threat to the eco-system.
Juveniles hunt in groups. While transforming to adulthood the level of aggression towards other specimens and other fishspecies increases, after which they start a solitary life or live as a couple. Young specimens can combined with conspecifics and other fish, under the condition that they grow up together. Newly introduced fish often will be killed instantly. In the end most of the other meet a similar fate when a couple has been formed. That said there are many different reports concerning combining this species with other fish, varying from sero tolerance toward other fish to totally non-aggressive. Perhaps this is also due to the geographic differences within the species.
Because of its size Channa marulius is not quite a suitable fish for keeping in a aquarium. To maintain a mature couple a very large aquarium (about 4 meter) is necessary. Dense planted areas with a lot of swimmingroom is needed and serveral dark spots are appreciated. Not many aquariast will be able or that devoted to offer such a large aquarium to 1 of 2 fish. From 50 cm and larger Channa marulius can become quite dangerous while feeding or maintenance.
Temperature can be set between 24-28 degrees Celsius. General hardness and pH values are not critical – just avoid extremes.
A common misconception is that air breathing fish live in stagnant, foul water in the wild and that clean water conditions are therefore not necessary in the aquarium. While most species can tolerate a wide range of water conditions, many fare poorly when water conditions deteriorate or undergo rapid changes (as in a massive waterchange). A lot of snakeheads are lost by beginner or advanced aquarist because of massive waterchanges and too rapid tank introduction. 15% waterchange a week should be ok. Good filtration is necessary, otherwise the amount of food will deteriorate the water fast.
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. Young snakeheads need feeding on a daily basis while they are growing, but once they reach 50 cm, 2-4 feeds a week will do fine. These fish do not require daily feeding as commonly believed. In fact, a fasting period for proper digestion is a healthy way to avoid internal bacterial growth and constipation which may likely result in bloating.
Grown fish should be fed using forceps to prevent injury – to the human.
Breeding Channa marulioidis requires space, especially for maintaining a lot of young fish. After 2 years (40-50 cm) sexual maturity is reached. Eggs are laid in substrate first and will raise to the surface. Parents will show extensive and enduring parental care until the young are about 10 cm. When the young become freeswimming, parents will take them on tour, similar to ducks with their sibblings. Parents defend their young with force. During this period they will attack anything that moves within of near the aquarium. In the natural habitat even swimming people can be attacked and wounded. When not enough space is offered, sometimes parents will attack each other.
Patrick de Pijper