Arapaima

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Arapaima
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Osteoglossiformes
Family: Osteoglossidae
Subfamily: Heterotidinae
Genus: Arapaima
J. P. Müller, 1843
Species: A. gigas
Binomial name
Arapaima gigas
(Schinz, 1822)

The arapaima, pirarucu, or paiche (Arapaima gigas) is a South American tropical freshwater fish. It is one of the largest freshwater fish in the world.

Contents

Species [edit]

A. gigas is the only generally-recognized species of the arapaima. In 1829, Swiss biologist Louis Agassiz produced a monograph of another proposed species found in the Brazilian Amazon and named A. agassizii in 1847.[2] Other proposed species include A. arapaima from Guyana and A. mapae from northeastern Brazil.[2]

Anatomy and morphology [edit]

Arapaima shown in its full length.

Arapaima can reach lengths of more than 2 m (6.6 ft), in some exceptional cases even more than 2.5 m (8.2 ft) and over 100 kg (220 lbs).The maximum-cited weight for the species is 200 kg (440 lbs). As one of the most sought after food fish species in South America, it is often captured primarily by handheld nets for export, by spearfishing for local consumption, and, consequently, large arapaima of more than 2 m are seldom found in the wild today.

Aside from its immense size, perhaps the most peculiar trait of the arapaima is a fundamental dependence on surface air to breathe. In addition to gills, it has a modified and enlarged swim bladder, composed of lung-like tissue, which enables it to extract oxygen from the air. This is an adaptation to the often hypoxic conditions of the Amazon floodplains, but requires the arapaima to surface for air every 5 to 15 minutes.[3]

Fishing [edit]

Skull from side and above

Commercial fishing of the arapaima has been banned by the Brazilian government due to its commercial extinction. Fishing is allowed only in certain remote areas of the Amazon basin, and must be catch-and-release, or harvesting by native peoples for consumption. Because the arapaima produces "large, boneless fish steaks",[4] it is considered a delicacy; some 7000 tons per year were taken from 1918 to 1924, the height of its commercial fishing. The demand for the arapaima has led to farming of the fish by the "ribeirinhos" (as Brazilians call those living on the riverbanks).[5]

Ecology [edit]

The diet of the arapaima consists of fish, crustaceans, even small land animals that walk near the shore. The fish is an air-breather, using its labyrinth organ, which is rich in blood vessels and opens into the fish's mouth,[6] an advantage in oxygen-deprived water that is often found in the Amazon River. This fish is therefore able to survive in oxbow lakes with dissolved oxygen as low as 0.5 ppm. In the wetlands of the Araguaia, one of the most important refuges for this species, it is the top predator in such lakes during the low water season, when the lakes are isolated from the rivers and oxygen levels drop, rendering its prey lethargic and vulnerable.

Reproduction [edit]

Due to the geographic range that arapaima inhabit, the animal's life cycle is greatly affected by the seasonal flooding that occurs. The arapaima lays its eggs during the months when the water levels are low or beginning to rise. They build a nest approximately 50 cm wide and 15 cm deep, usually in muddy bottomed areas. As the water rises the eggs hatch and the offspring have the flood season to prosper, during the months of May to August. Therefore, the yearly spawning is regulated seasonally. The arapaima male is supposed to be a mouthbrooder, like its relative the Osteoglossum, meaning the young are protected in its mouth until they are older. The female arapaima helps to protect the male and the young by circling them and fending off potential predators.

In his book The Whispering Land, naturalist Gerald Durrell reports hearing the tale in Argentina that female arapaima have been seen secreting a white substance from a gland in the head and that their young have been noted seemingly feeding on the substance.

Evolutionary history [edit]

Fossils of arapaima or a very similar species have been found in the Miocene Villavieja Formation of Colombia.[7]

Importance to humans [edit]

Closeup of scales

The arapaima is hunted and utilized in many ways by local human populations. Arapaima are harpooned or caught in large nets, and the meat is said to be delicious. Since the arapaima needs to swim up to breathe air, traditional arapaima fishers often catch them by first harpooning them and then clubbing them dead. One individual can yield as much as 70 kg of meat.

The arapaima has also been introduced for fishing in Thailand and Malaysia. Fishing for this species in Thailand can be done in several lakes, where one often sees arapaima over 150 kg landed and then released.

Special care is needed when dealing with these fish as, since they are large, they can be hard to handle. With catch and release after the fish is landed, it must be held for 5 minutes until it takes a breath. The fish has a large blood vessel running down its spine and lifting the fish clear of the water for trophy shots can rupture this vessel causing death. Arapaimas are also known to leap out of the water if they feel constrained by their environment or harassed.

It is also considered an aquarium fish, although it obviously requires a large tank and ample resources. In addition, this animal appears in the pet trade, although keeping an arapaima correctly requires a large tank and can prove quite difficult.

The tongue of this fish is thought to have medicinal qualities in South America. It is dried and combined with guarana bark, which is grated and mixed into water. Doses of this are given to kill intestinal worms. In addition, the arapaima's bony tongue is often used to scrape cylinders of dried guarana, an ingredient in some beverages, and the bony scales are used as nail files.

In the Amazon region, the locals often salt and dry the meat, rolling it into a cigar-style package that is then tied, and can be stored for a long time without rotting, which is very important in a region where few have refrigeration. This is often referred to as the "Cod of the Amazon", and can be prepared in the same way as the traditional salted cod is prepared.

In July 2009, some villagers who live around Kenyir Lake in Terengganu, Malaysia, reported sighting the arapaima gigas. The "Kenyir Monster," or "dragon fish" as the locals call it, was claimed to be responsible for the mysterious drowning of two men on June 17.[8]

In popular culture [edit]

Arapaima depicted on a 1954 postage stamp of British Guiana

Gallery [edit]

See also [edit]

References [edit]

  1. ^ World Conservation Monitoring Centre (1996). Arapaima gigas. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 13 March 2009. Database entry includes a little information for why this species is data-deficient.
  2. ^ a b "Long-Lost Giant Fish from Amazon Rediscovered". Science Daily. April 22, 2013. 
  3. ^ http://www.arkive.org/arapaima/arapaima-gigas/#speciesFactFile
  4. ^ Comment by extreme angler Jeremy Wade in River Monsters episode name: "Unhooked", Animal Planet, 16 July 2010 10AM PDT.
  5. ^ River Monsters episode name: "Unhooked", Animal Planet, 16 July 2010 10AM PDT.
  6. ^ Ferraris, C.J. (2003). "Family Arapaimatidae". In Reis, R.E., Kullander, S.O., Ferraris, C.J. Check List of the Freshwater Fishes of South and Central America. Porto Alegre, Brazil: EDIPUCRS. pp. 582–588. 
  7. ^ Lundberg, J.G. and B. Chernoff (1992). "A Miocene fossil of the Amazonian fish Arapaima (Teleostei, Arapaimidae) from the Magdalena River region of Colombia--Biogeographic and evolutionary implications". Biotropica 24 (1): 2–14. doi:10.2307/2388468. JSTOR 2388468. 
  8. ^ Giant fish sighthings in Kenyir Lake

Bibliography [edit]

External links [edit]

Wikispecies has information related to: Arapaima gigas
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