The iridescent shark, iridescent shark catfish (''Pangasianodon hypophthalmus'') is a species of

shark catfish The shark catfishes form the family Pangasiidae. They are found in fresh and brackish waters across southern Asia, from Pakistan to Borneo. Among the 30-odd members of this family is the plant-eating, endangered Mekong giant catfish ''Pangasian ...

(family Pangasiidae) native to the rivers of

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...

. Despite its name, it is not a

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...

. It is found in the

Mekong The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annual ...

basin as well as the Chao Phraya River, and is heavily cultivated for food there. The meat is often marketed under the common name swai (from Thai สวาย). It has also been introduced into other river basins as a food source, and its striking appearance and iridescence have made it popular with

fishkeeping Fishkeeping is a popular hobby, practiced by aquarists, concerned with keeping fish in a home aquarium or garden pond. There is also a piscicultural fishkeeping industry, serving as a branch of agriculture. Origins of fishkeeping Fish hav ...

hobbyists, among whom it is also known as the Siamese shark catfish or sutchi catfish. The swai's

omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...

diet consists of

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can ...

s, other fish, and plant matter.

Names

The fish is named for the glow or iridescence exhibited in juveniles, as well as the

-like appearance of this and other

Description

Adults reach up to in length and can weigh up to a maximum of . They have a shiny, iridescent color that gives these fish their name. However, large adults are uniformly grey. The fins are dark grey or black. Juveniles have a black stripe along the lateral line and a second black stripe below the lateral line.

Distribution and habitat

Iridescent sharks originate from the large

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

Chao Phraya The Chao Phraya ( or ; th, แม่น้ำเจ้าพระยา, , or ) is the major river in Thailand, with its low alluvial plain forming the centre of the country. It flows through Bangkok and then into the Gulf of Thailand. E ...

and

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

, though they have been introduced into other rivers for aquaculture. They are a freshwater fish that natively live in a

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

climate and prefer water with a 6.5–7.5 pH, a water hardness of 2.0–29 dGH, and a temperature range of . They prefer large bodies of water similar to the deep waters of their native Mekong river basin. The iridescent shark is a migratory fish that in most regions moves upstream to

spawn Spawn or spawning may refer to: * Spawn (biology), the eggs and sperm of aquatic animals Arts, entertainment, and media * Spawn (character), a fictional character in the comic series of the same name and in the associated franchise ** '' Spawn: ...

during the flood season while the waters are high and returns downstream to seek rearing habitats when the river water levels recede. The dates of the migrations vary depending on the river system. In the Mekong river basin, they migrate upstream in May to July and return downstream during September through December. South of the

Khone Falls The Khone Falls and Pha Pheng Falls ( lo, ນ້ຳຕົກຕາດຄອນພະເພັງ; km, ល្បាក់ខោន, ''Lbak Khaon'') together form a waterfall located in Champasak Province on the Mekong River in southern Laos, nea ...

, upstream migration occurs in October to February, with its peak in November to December; here, it appears to be triggered by receding waters at the end of the flood season. In August 2015, an environmental group in Santander Department, Santander, Colombia, confirmed that iridescent sharks had been found in one of the tributaries that feed into the Magdalena River, having been accidentally introduced from illegal farm fisheries in the area. The find has caused alarm amongst the scientific community and government officials, as the Magdalena river is home to over 200 native fish species, 35 of which are endangered. Iridescent sharks are also introduced to other Southeast asia countries for food especially Peninsular Malaysia, Singapore, Indonesia and Myanmar, In Malaysia, Singapore and Indonesia they are called ikan patin (which 'ikan' means fish in malay and indonesian), Malaysian Chinese prefer them steamed or cooked in whole, while Malay prefer cooking these fishes with Tempoyak and Curry.

Culinary profile

Pangasius does not have a gourmet reputation and is sold cheaply as swai (, from Thai language, Thai สวาย ''s̄wāy'') in the United States, panga (or pangas) in Europe and cream dory and basa in several Asian countries and in the UK. Despite its lowly reputation, the total export of pangasius from Vietnam reached US$1.8 billion in 2014. Pangasius fillets are an increasingly popular product because of their low cost, mild taste and firm texture. Recipes for other whitefish (fisheries term), whitefish such as Sole (fish), sole or halibut can be adapted to pangasius. Pangasius is an Omnivore, omnivorous fish, and thus does not require a high level of animal protein in its diet. Typical grading sizes are , , and .

In the aquarium

While juvenile iridescent sharks are sold as pets for home aquariums, they are not easy fish to keep. Iridescent sharks are schooling fish that prefer groups, are accustomed to living in rivers, and are active fish that require space. They have very poor eyesight, so detected movement from outside of their habitat can be seen as a threat. If stressed, their first instinct is to flee; a blind dash can cause injury in an aquarium environment. These injuries may result in the fish sinking to the bottom, where it may lie on its side or back until it recovers. Iridescent sharks require a minimum tank size of to develop naturally. Schools require even larger tanks. If given enough room and fed adequately, they can reach in length. In most home aquaria, the lack of space stunts their growth. For this reason, most iridescent sharks kept in home aquaria grow to in length only and may die prematurely. When provided adequately sized aquaria and proper husbandry, iridescent sharks may live into their teens and grow to full size.Aqualand Pets
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References

External links

Planet Catfish
{{Taxonbar, from=Q312296 Pangasiidae Fish of the Mekong Basin Fish of Cambodia Fish of Laos Fish of Thailand Fish of Vietnam Commercial fish Fish described in 1878