Snakehead (fish)

Snakehead
Northern snakehead, Channa argus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Channidae
Genera
Channa Parachanna

Channidae is a family of freshwater perciform fish commonly known as snakeheads, and is native to Africa and Asia. There are two genera, Channa in Asia, and Parachanna in Africa, consisting of 30-35 species. These predatory fishes are distinguished by a long dorsal fin, small head with large head scales on top, large mouth and teeth. They have a physiological need to breathe atmospheric air, which they do with a suprabranchial organ: a primitive form of a labyrinth organ.

They are considered valuable food fish. Larger species like Channa striata, Channa maculata or Parachanna obscura are farmed in aquaculture. Snakeheads feed on plankton, aquatic insects, and mollusks when small. When adult, they mostly feed on other fish like carp, or frogs. In rare cases, small mammals such as rats are taken. The size of the snakehead species differs greatly. "Dwarf snakeheads" like Channa gachua grow to 10 inches (25 cm). Most snakeheads grow up to 2 or 3 ft. (60–100 cm). Only two species (Channa marulius and Channa micropeltes) can reach a length of more than 1 meter and a weight of more than 6 kg.

It is illegal to keep snakeheads as pets in thirteen states of the USA and other countries as they have become an invasive species due to irresponsible owners releasing them into the wild when they could/would no longer take care of them. If in an enclosed area they will try anything to escape. If in an aquarium they will charge at full force and tend to knock over the aquarium or shatter the glass.

Species

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Native Distribution of the family Channidae. Source: USGS 2004

There are about 30-35 species in two genera:

• Genus Channa
  • Borna snakehead, Channa amphibeus (McClelland, 1845).
  • Northern snakehead, Channa argus (Cantor, 1842).
  • Channa asiatica (Linnaeus, 1758).
  • Channa aurantimaculata Musikasinthorn, 2000.
  • Channa bankanensis (Bleeker, 1852).
  • Barca snakehead, Channa barca (Hamilton, 1822).
  • Rainbow snakehead, Channa bleheri Vierke, 1991.
  • Channa burmanica Chaudhuri, 1916.
  • Channa cyanospilos (Bleeker, 1853).
  • Channa gachua (Hamilton, 1822).
  • Channa harcourtbutleri (Annandale, 1918).
  • Forest snakehead, Channa lucius (Cuvier, 1831).
  • Channa maculata (Lacépède, 1801).
  • Channa marulioides (Bleeker, 1851).
  • Great snakehead, Channa marulius (Hamilton, 1822).
  • Channa melanoptera (Bleeker, 1855).
  • Black snakehead, Channa melasoma (Bleeker, 1851).
  • Giant snakehead, Channa micropeltes (Cuvier, 1831).
  • Channa nox Zhang, Musikasinthorn & Watanabe, 2002.
  • Walking snakehead, Channa orientalis Bloch & Schneider, 1801.
  • Channa ornatipinnis Britz, 2007.
  • Channa panaw Musikasinthorn, 1998.
  • Channa pleurophthalmus (Bleeker, 1851).
  • Channa pulchra Britz, 2007.
  • Spotted snakehead, Channa punctata (Bloch, 1793).
  • Assamese snakehead, Channa stewartii (Playfair, 1867).
  • Snakehead murrel, Channa striata (Bloch, 1793).
• Genus Parachanna
  • Parachanna africana (Steindachner, 1879).
  • Parachanna insignis (Sauvage, 1884).
  • †Parachanna fayumensis Murray, 2006. (fossil)
  • Obscure snakehead, Parachanna obscura (Günther, 1861).

Ecological concerns

Snakeheads can become invasive species and cause ecological damage because they are top-level predators, meaning that they have no natural enemies outside of their native environment. Not only can they breathe atmospheric air, but they can also survive on land for up to 4 days, provided they are wet, and are known to migrate on wet land to other bodies of water by wriggling with their body and fins.

Snakeheads became a national news topic in the US because of the appearance of northern snakeheads spawning in a Maryland pond in 2002. Northern snakeheads became permanently established in the Potomac River around 2004, and possibly established in Florida. Apparently non-established specimens have been found in Flushing Meadows-Corona Park, New York, two ponds outside Philadelphia, Pennsylvania a pond in Massachusetts, and reservoirs in California and North Carolina.

They are prohibited in several other countries, like Australia, because their introduction to new ecosystems may displace indigenous species. Humans have been introducing snakeheads to non-indigenous waters for over 100 years. In parts of Asia and Africa, the snakehead is considered a valuable food fish and is produced in aquacultures. Due to this fact it was introduced either on purpose (fisheries motivation) or by ignorance (as was the case in Crofton).

Some examples of the introduction of snakeheads to non-indigeneous waters include:

• Channa maculata was introduced to Madagascar and to Hawaii around the end of the 19th century. It can still be found there today.
• Channa striata was introduced to islands east of the Wallace line by governmental programs in the later half of the 20th century. In Fiji, the introduction failed.
• Channa asiatica, which is native to southern China, was introduced to Taiwan and to southern Japan. In this case the origin and reason of the introduction is unknown, but most probably due to human intervention.
• Channa argus, which is native to northern China (Amur River), was introduced to Central Asia (Kazakhstan, Turkmenistan, Uzbekistan). It was introduced to Japan about 100 years ago due to fisheries motivations. Its introduction to Czechoslovakia by the government in the 1960s failed due to cold winters.

A comprehensive work on the dangers of the introduction of snakeheads to non-indigeneous waters is that of Prof. W. Courtenay.

Other Sightings in the U.S.

In what was determined by the Army Corps of Engineers to be an "isolated incident"., a fisherman caught a single snakehead on October 9, 2004 while fishing from Lake Michigan at Burnham Harbor in Chicago, Illinois. Snakeheads have also been spotted in Alabama, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Idaho, Kentucky, Mississippi, Nevada, North Carolina, Oregon, Pennsylvania, Texas, Utah, and Washington.

Sightings in the UK

On February 19, 2008 it was reported that a snakehead weighing almost Template:Lb to kg was caught in the River Witham near North Hykeham, Lincolnshire. The Angler's Mail confirmed it was a giant snakehead Channa micropeltes. This subsequently turned out to be a hoax. The Norfolk Eastern Daily Press reported in March:

Expert opinion from fish scientists insisted this warm water species could never survive in the icy Lincolnshire river for more than a few seconds. It has since been discovered the snakehead was actually dead laying in a Lincoln street and the finder preserved it in a domestic freezer until the following weekend when the misleading pictures were taken.

Removal

Snakeheads may be exterminated by applying the herbicides diquat dibromide and glyphosate (tradenames such as Roundup, Rodeo) to ponds to eliminate aquatic vegetation. The death of aquatic plants causes dissolved oxygen levels to drop, and a subsequent fish kill occurs.

Approximately one to two weeks after the application of the herbicides, application of the piscicide Rotenone kills any remaining fish. Dead fish should be removed daily; however, unpleasant odors from decaying organic material are to be expected.

References

• Froese, Rainer; Pauly, Daniel (eds.). "Family Channidae". FishBase. January 2006 version.
• "Channidae". Integrated Taxonomic Information System. 20 March. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)

External links

• About.com's article on Snakeheads
• snakeheads.org world's largest website for snakeheads
• Overview of Northern Snakehead biology
• Student article on Snakehead problem in Florida
• Fish or Foul: Snakeheads near Washington, D.C., and the people who love them