The iridescent shark, iridescent shark catfish (''Pangasianodon hypophthalmus'') is a species of
shark catfish (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 United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...
. 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 annuall ...
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
Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfly ...
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 ha ...
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 gro ...
s, other fish, and plant matter.
Names
The fish is named for the glow or
iridescence
Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfly ...
exhibited in juveniles, as well as the
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 ...
-like appearance of this and other
shark catfish.
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
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the ...
s
Chao Phraya and
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 annuall ...
in
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 ...
, though they have been introduced into other rivers for aquaculture. They are a
freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does in ...
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
Degrees of general hardness (dGH or °GH) is a unit of water hardness, specifically of general hardness. General hardness is a measure of the concentration of divalent metal ions such as calcium (Ca2+) and magnesium (Mg2+) per volume of water. S ...
, 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 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, 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,
Colombia, confirmed that iridescent sharks had been found in one of the tributaries that feed into the
Magdalena River
The Magdalena River ( es, Río Magdalena, ; less commonly ) is the main river of Colombia, flowing northward about through the western half of the country. It takes its name from the biblical figure Mary Magdalene. It is navigable through much o ...
, 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
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 United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...
countries for food especially
Peninsular Malaysia
Peninsular Malaysia ( ms, Semenanjung Malaysia; Jawi: سمننجڠ مليسيا), or the States of Malaya ( ms, Negeri-negeri Tanah Melayu; Jawi: نڬري-نڬري تانه ملايو), also known as West Malaysia or the Malaysian Peninsula, ...
,
Singapore
Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...
,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
and
Myanmar
Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
, 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
Tempoyak ( Jawi: تمڤويق), asam durian or pekasam is a Malay condiment made from fermented durian. It is usually consumed by the ethnic Malays in Maritime Southeast Asia, notably in Indonesia and Malaysia. Tempoyak is made by taking the f ...
and
Curry
A curry is a dish with a sauce seasoned with spices, mainly associated with South Asian cuisine. In southern India, leaves from the curry tree may be included.
There are many varieties of curry. The choice of spices for each dish in trad ...
.
Culinary profile

Pangasius does not have a gourmet reputation and is sold cheaply as swai (, from
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 such as
sole or
halibut
Halibut is the common name for three flatfish in the genera '' Hippoglossus'' and '' Reinhardtius'' from the family of right-eye flounders and, in some regions, and less commonly, other species of large flatfish.
The word is derived from ''h ...
can be adapted to pangasius.
Pangasius is an
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 ...
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]
/ref>
See also
*List of freshwater aquarium fish species
A vast number of aquatic species have successfully adapted to live in the freshwater aquarium. This list gives some examples of the most common species found in home aquariums.
Catfish
Characins and other characiformes
...
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