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 Channa family includes 31 species widely distributed in Asia from southeastern Iran and eastern Afghanistan eastward through Pakistan, India, southern Nepal, Bangladesh, Myanmar, Thailand, Laos, Malaysia, Sumatra, Indonesia, Vietnam, Korea, and China to and with part of Siberia. In addition, 3 species of the related Parachanna family are found locally in parts of Africa.
De Channa soorten kennen grote verschillen in formaat. De onofficiële term Dwerg Slangekopvissen is door aquariumhouders bedacht om een groep van Channa soorten te duiden die niet groter worden dan 25 cm: Channa bleheri, Channa cachua, Channa orientalis, Channa andrao. Deze soorten zijn vanwege de beperkte omvang en het relatief vreedzame karakter ook het meest geschikt voor het houden in een aquarium.De meeste anders soorten worden maximaal 30-90 centimeter. Vijf soorten (Channa argus, Channa barca, Channa marulius, Channa micropeltes en Channa striata) kunnen zelfs 100 centimeter of groter worden en kunnen als monstervissen worden beschouwd die nauwelijks geschikt zijn voor het houden in een aquarium.
Origin
Fossils dating back 50 million years indicate an origin in the southern Himalayas (India and eastern Pakistan). From 15 million years ago, with the expanding intertropical climate zone, they have spread further to parts of Europe, Africa, and a wider area of Asia.
Appearance
Snakehead fish have an elongated body and can be recognized by a long continuous dorsal fin, a large flat head, and a mouth filled with teeth. The name snakehead fish comes from the flattened head and the large scales on the head.
Snakehead fish, like most fish, have gills to extract oxygen from the water. They can extract oxygen from the air. In fact, snakehead fish mainly get oxygen from the air. Without air, they would drown. Unlike most other air-breathing fish, snakehead fish have a number of cavities in the back of the head. These cavities (suprabranchial chambers) are filled with tightly folded sheets. Due to the large contact surface of the sheets, oxygen can be absorbed into their blood. Unlike mammals and reptiles, there is no diaphragm and they must use water to exchange used oxygen for fresh oxygen with each mouthful of air. This limits the possibility of absorbing oxygen outside the water. Snakehead fish seem to gasp for more air when they are more active.
The Parachanna family (from parts of Africa) has been recognized as a separate family due to a more primitive implementation of the breathing apparatus.
Snakehead fish are known for being able to migrate short distances over land to find other bodies of water, taking advantage of the ability to breathe air. To move over land, they curve their bodies into an S-shape, then stretch with force to propel themselves forward. Snakehead fish can survive out of water for 2 to 4 days at high humidity. In full sunlight, however, they stun within minutes and die within hours. Contrary to popular belief, snakehead fish don’t just leave the water. They especially know how to find their way back to the water when previously abundant areas dry up again. The only snakehead fish that actively leave the water belong to the dwarf species (C. gachau and C. orientalis, C. asiatica, and C. amphibius). Even then there is a clear reason for leaving the water, such as escaping overpopulation.
Snakeheads can be found in a wide variety of waters and water conditions. They are found in tropical, subtropical and temperate regions. Snakehead fish are not dependent on the oxygen level in the water. Many (not all) species can also tolerate widely varying temperatures and water parameters for a period of time. However, they are very vulnerable to sudden changes in water parameters.
Commercial interest
Snakehead fish are important consumption fish, especially in India, Southeast Asia, China and to a lesser extent Africa. It has been fished on a large scale for centuries. In recent decades, certain species (C. maculata, P. obscura, C. striata, C. argus) have been cultivated for consumption. Sometimes they are used by fish farmers to reduce “pest fish” such as Tilapia.
In Southeast Asia, markets are often overrun with snakehead fish. Fishermen and sellers take advantage of the fish’s ability to survive in just a thin film of water. This means that fresh fish can be offered throughout the day, a nice bonus in the not-always-hygienic conditions of a warm market.
Scientific research shows that snakehead fish contain natural anti-inflammatories. In addition, it is known that they have a high content of omega-6 fatty acids, which have an analgesic effect. The fish oil also has positive effects on the prevention of cardiovascular disease and cancers.
“Fish out of hell”
Partly as a result of colonization, snakehead fish have been deliberately introduced to other areas (Madagascar, Hawaii, Taiwan, Japan, Kazakhstan, Turkmenistan, Uzbekistan, and the Czech Republic) over the past hundred years. Today, snakehead fish are considered a major threat to local ecosystems. Especially in the absence of natural enemies (such as humans), they are very invasive and destructive. Large species become sexually mature after 2-3 years, mate up to 2-5 times a year, and produce up to 15,000 eggs at a time. In addition, they are considered capable of migrating overland to other water systems. C. argus in particular is thought to be able to double its population within 15 months.
The discovery of a number of species of snakehead fish in US waters has caused quite a stir. The media has been used to take unpopular measures to prevent the further spread of the species (such as draining or completely poisoning). Various media created a Piranha-esque image of a monster fish that eats an entire lake, then moves overland to the next lake, preying on dogs and children along the way. National Geographic came out with a slightly more fact-based documentary Invasion of the Snakeheads that talked about Fishzilla. Filmmakers in Hollywood found inspiration and support for 2 horror films in the hype.
Asian food markets (and the related need to store live fish in natural fish ponds) were blamed for the invasion. With the availability as food fish, they also became available to aquarium and pond keepers. Fish that grew too big for the tank often ended up in the local ecosystem. Since 2002, many US states have banned the possession of live snakehead fish. In Europe, too, an import permit is required for C. argus, because this species is able to thrive in our colder waters.
Behavior
Snakehead fish are predatory fish that feed on plankton, insects, and snails as youngsters. As they grow larger, the larger species switch to a menu consisting mainly of fish, frogs, crabs, shrimps, small aquatic mammals and waterfowl. Young specimens usually hunt in groups. When they reach sexual maturity, they isolate themselves to lead a solitary life or to live in pairs. They then develop a higher degree of aggression towards conspecifics and often also towards other fish. Often a couple will not tolerate other fish in the limited space of an aquarium.
Snakehead fish are not active swimmers. In addition to hunting, they actively move only to draw air from the surface. Usually, they swim in the middle water layer or rest on the bottom to strike from an ambush. A number of species, however, are pelagic and are more active swimmers. All snakehead fish are capable of launching themselves forward from a standstill by briefly curving their muscular body and stretching it forcefully.
Brood care is an important behavioral trait for snakehead fish. All species violently guard and defend their eggs and young. The majority of species lay eggs that rise to the surface and are guarded there. A number of smaller species collect these eggs and store them in a burrow that may or may not have been dug. A number of species are mouthbrooders.
The snakehead fish is a popular – eccentric – fish among a specialist group of aquarium keepers. Snakehead fish are elegant, powerful, alert and calm fish, with a willful character. The mutual communication, hunting technique, and brood care are fascinating. Some aquarium keepers specialize in keeping the largest species and have a pet-like experience. Some rare and variegated species (such as C. barca) are among the most valuable aquarium fish on the market.
Snakehead fish often have changing patterns and colors as they grow. With the exception of the dwarf species, the young of most species are much more beautifully marked and colored than the aging animals. With age, the animals usually get a duller ground color. Some aquarium keepers lose interest in the fish as they grow. It is therefore wise to do some research before purchasing.
As predators, snakeheads are by nature not a suitable choice for the average community aquarium. They are intolerant and usually soon the only fish. A special aquarium is required for keeping snakehead fish. Aquarium keepers have different experiences when it comes to mixing snakehead fish with other tankmates. Most species are best kept alone. Combining snakehead fish with territorial or aggressive tankmates is not recommended. An intimidated snakehead fish hides, tries to escape and refuses to eat.
The extent to which other fish are tolerated in the small habitat of an aquarium depends very much on the species, but within that probably also on the individual specimen and the specific situation. There are a number of general experiences per group:
Dwarf species
Due to their small size and relatively mild temperament, most dwarf species pair well with robust, fast fish of a similar size. Provided these fish are not too territorial or aggressive. It should be taken into account that most dwarf snakeheads live in their natural environment in an eco climate zone with seasonal extremes in water temperature and water values. As a result, they cannot be kept at a tropical temperature all year round. A temperature reduction for at least one season per year is necessary to keep them healthy. Co-residents must also be able to cope with this.
Medium sized species
This group contains the most diversity in terms of behaviour. Many of the larger species (between 30-60 cm) can be combined with relatively fast and robust fish of a similar size, for example large cyprinids. General experience is that combining with other fish species works best when the snakehead fish are not yet too big and when the other fish have already settled. Newly introduced fish are often killed immediately. It varies greatly by species and experience. Often the tolerance to other fish is temporary. When a pair of snakehead fish is formed, the co-inhabitants (also conspecifics) are usually chased and killed.
Large species (60 – 130 cm)
These snakehead fish themselves require an amount of space that most private aquariums are unlikely to be able to provide. Extremely large private aquariums are usually just big enough to hold one fish or a couple. In general, the same applies as with the medium varieties. Fish that grow with them from an early age are often tolerated. Newly introduced fellow residents are often killed immediately.
A number of large species, such as C. argus and C. micropeltes, are important food fish. They are considered highly invasive and destructive to the local ecosystem outside their natural habitat (see also the documentary Invasion of the Snakeheads). After the fish were sighted in several places in the US, import bans and a ban on owning a live specimen are in effect in most states within the US.
Channa asiatica – Chinese Snakehead
With a maximum length of 35 cm, Channa asiatica is a relatively small Snakehead. The species occurs in central and southern China (the Yangtze as the northern border area) and in the Sông Cái river in northern Vietnam. Furthermore, the species is present on the island of Hainan and Hong Kong. In addition, the species has been introduced to Taiwan and a number of islands belonging to Japan.
The habitat has a tropical monsoon rainforest climate. Characteristics are heavy rainfall, high humidity, and warm summer temperatures. The water temperature drops below 19 degrees Celsius in winter and rises between 22-28 degrees Celsius in summer (preferably keep it lower than this maximum). If it is kept at a higher temperature for too long, (fatal) bacterial infections often occur in the long term.
Channa asiatica is a mouthbrooder. The difference between males and females is hard to see. Females grow more slowly than males.
It is best to keep this species as a couple or solitary. To form a couple, as with almost all snakehead fish, it is best to purchase a group of young fish. When a couple has been formed, the other fish must be caught (otherwise they will be killed). However, keeping a group of this species requires a very large aquarium, lots of hiding places and luck. Experience with this species is that they are already intolerant of conspecifics from a young age and that they can cause great damage to each other in confrontations. Only when a couple has been formed do the confrontations between those 2 individuals stop, usually a very close couple is created. However, there are known cases where aggressiveness occurs after mating and one of them is killed. In an aquarium it is always wise to have a separation ready in case things go wrong.
Experiences with Channa asiatica in combination with other fish species vary. Sometimes it works, but in most cases the outcome is that keeping with other fish is not a long-term success and that larger co-inhabitants also end up skinned or in pieces.
Channa asiatica is, compared to other snakehead fish, a fairly active swimming species
The aquarium
An aquarium with densely planted areas, open swimming areas, and plenty of hiding places. Floating plants contribute to the fish’s comfort. Some darker spots are appreciated. Make sure that it is possible for them to get air from the surface, otherwise, they will suffocate. Close the aquarium tightly. They manage to escape from the aquarium through the smallest hole. Make sure that the aquarium temperature is lowered to 15-20 degrees Celsius during a season. In the colder period, less food is required and the water level can drop slightly. It is also possible to reverse the summer and winter seasons by keeping Channa Asiatica in the outdoor pond during the summer months.
Snakehead fish can live in water of very different composition. However, they are poorly resistant to sudden changes. Therefore, change small amounts of water at once.
Any co-residents must be able to withstand the necessary temperature reduction in winter.
Diet
The Chinese Snakehead is a carnivore. All common fish food is eaten, including frozen. They will not feed on dry food like flakes or granules.
Breeding Channa asiatica – Chines Snakehead
Experience is that a well-fed couple from 18 cm in length breeds at least once a year. Normally this can take place every 6-8 days in the aquarium. Mating usually takes place at night. Usually, this happens at a water temperature of around 18 degrees Celsius. Famales then get a paler base color with a pink glow. The dark brown stripes and silver markings darken. Males become darker in color.
The eggs float to the surface, where they are guarded by both parents. Depending on the temperature, the young hatch between 24-23 hours. They are then between 6-7 mm long and hunt in the same way as the parents. They eat brine shrimp larvae and daphnia directly. After 1 or 2 weeks you can switch to mosquito larvae.
If the intention is to keep as many youngsters as possible, it is important to sort them weekly according to size. The young are small cannibals, eating their own siblings.
Video
Author
Patrick de Pijper
Copyright images
Tea Shyi Kai: https://instagram.com/shyikai_photography/ en https://www.flickr.com/photos/78795430@N08
Hung Jou Chen
AquariumGlaser.de
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