Channidae

Snakeheads are primitive predatory fish from the Channidae family, a group within the group of bass. The exact ancestry is unknown, although snakehead fish are considered closely related to the labyrinth fish (Anabantoid) and the Synbranchus eels (including the spiny eels) after recent research.

The Channa family includes 31 species that are widespread 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 up to and including part of Siberia. In addition, 3 species of the related Parachanna family are found locally in parts of Africa.

The Channa varieties have large differences in size. The unofficial term dwarf snakehead fish was coined by aquarists to refer to a group of Channa species that do not grow larger than 25 cm: C. bleheri, C. cachua, C. orientalis, C andrao. These species are also most suitable for keeping in an aquarium due to their limited size and relatively peaceful character. Most other species grow to a maximum of 30-90 cm. Five species (A. argus. C. barca, C. marulius, C. micropeltes and C. striata) can even grow up to 100 cm and can be considered monster fish that are hardly suitable for keeping in an 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, the animals have spread further to parts of Europe, Africa and a wider area of Asia.

Appearance characteristics

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. Young animals and adult animals can additionally also 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 content in the water. Many (not all) species can also tolerate widely varying temperatures and water values for a period of time. However, they are very vulnerable to sudden changes in them.

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” like 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 the fish has a high content of omega 6 fatty acids, which have an analgesic effect. The fish oil also has positive effects for 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 in the past hundred years (Madagascar, Hawaii, Taiwan, Japan, Kazakhstan, Turkmenistan, Uzbekistan and the Czech Republic). 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 which 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, the animals also became available to aquarium and pond keepers. Animals 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 animals 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 cross 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 is fascinating. Some aquarium keepers specialize in keeping the largest species and have a pet-like experience. Some rare and colorful 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 animals 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 ecoclimate 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 the animals 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 1 animal or a couple. In general, the same applies as with the medium varieties. Fish that grow with you from an early age are often tolerated. Newly introduced inmates are often killed immediately.