September 22, 2008

Snake Head or "Ikan Gabus , Betutu, Ikan malas"

Common Snakehead

The Common Snakehead or Aruan is the most easily encountered of all Channa species. It is considered good eating and has medicinal value as a soup tonic; it is easily found in many Southeast Asian markets.

The species inhabits a variety of waterways including ponds, lakes, streams and drains. The dorsal side is brown in colour, the flanks have faint, slightly oblique bands, and the belly is white. Juveniles are more orange in colour. As with the Giant Snakehead Channa micropeltes, the juvenile fish are raised in a well protected underwater nest.

The species ranges throughout the Indian Subcontinent and Southeast Asia and has been introduced into many waterways.

Channidae is a family of freshwater fish commonly known as snakeheads, and is native to Africa and Asia. There are two extant 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.Channidae is also known as the the Northern Snakehead, or Channa Argus, and is native to Asia. There are 29 known Snakehead varieties.

The National Geographic Channel reported:

A Northern Snakehead reaches sexual maturity by age 2 or 3. Each spawning-age female can release up to 15,000 eggs at once. Snakeheads can mate as often as five times a year. This means in just two years, a single female can release up to 150,000 eggs...

'They can travel across land and live out of water for up to three days,' [says U.S. Secretary of the Interior Gale Norton].

[Snakeheads can breathe air unlike other fish as they] use a primitive lung above their gills... [or] 'air chambers'.

Out of the water Snakeheads rhythmically move their fins and muscular bodies back and forth: the fish equivalent of walking... It's a resourceful adaptation. [In their native Asia they must survive both wet and dry weather cycles like monsoons and droughts.]

When the Snakehead eats it is a thrust predator. It will eat its prey all at once, striking and ingesting it whole.

The Giant Snakehead, or Channa micropeltes, is native throughout Asia, and is the most aggressive Snakehead. They can grow to over 1.5 metres long. Adult Snakeheads force their hatchlings to breathe air by pushing them to the surface.

From 2002 to 2003, one Los Angeles supermarket was found to have sold approximately 25,000 dollars worth of illegal live Snakeheads which caused breakouts in local eco systems.

It has had recent sightings in Lincolnshire (UK) (which proved to be hoax) and in the U.S. National Geographic referred to it as "Fishzilla".

Prehistory and evolution

Channidae are well-represented in the fossil record and known from numerous specimens. Research indicates that snakeheads likely originated in the south Himalayan region (modern-day Pakistan) at least 50 million years ago, during the Early Eocene epoch. By 17 Ma, during the Early Miocene, Channidae had spread into western and central Eurasia, and by 8 Ma, during the late Tortonian, they could be found throughout Africa and East Asia. As Channidae are adapted to climates of high precipitation with mean temperatures of 20 °C (68 °F), their migrations into Europe and Asia correspond to the development of the Intertropical Convergence Zone, which increased air humidity, and the intensification of the East Asian monsoon, respectively. Both weather patterns emerged due to greater vertical growth of the Alps, Pyrenees, and Himalayas, which affected Eurasian climactic patterns.

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 four 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, as well as Wawayanda, 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.


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