Iridescent shark
Encyclopedia
The iridescent shark is a species of shark catfish
(family Pangasiidae) native to the rivers of Southeast Asia
. It is found in the Mekong
basin as well as the Chao Phraya River
, and is heavily cultivated for food there. It has also been introduced into other river basins as a food source, and its striking appearance and iridescence
have made it common in the fishkeeping
hobby. Their omnivorous diet consists of crustacean
s, other fish, and plant matter.
exhibited in juveniles, as well as the shark
-like appearance of this and other shark catfish
. It is also known as Siamese shark or sutchi catfish in the aquarium
hobby or as tra, swai , or striped catfish in the food fish market, and occasionally incorrectly as basa and panga (these names should be rather used for Pangasius bocourti and Pterogymnus laniarius, respectively).
s Chao Phraya and Mekong
in Asia
, though they have been introduced into other rivers for aquaculture. They are a freshwater
fish that natively live in a tropical climate and prefer water with a 6.5–7.5 pH
, a water hardness of 2.0–29.0 dGH
, and a temperature range of 22–26 °C (71.6–78.8 °F). 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 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. Upstream migration in this species appears to be triggered by receding waters. At the end of the flood season, the fish migrate back downstream away from flooded waters. 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.
P. hypophthalmus is an important food fish and is farmed extensively in many parts of the world. It is one of the most important aquaculture
species in Thailand and Vietnam. Along with other farm-raised shark catfish
es, it has caused much debate within the U.S., with legislation passed recently to prevent its imports from cutting into American farmed catfish sales. Prohibited to be labelled as "catfish" in the U.S., P. hypophthalmus is now labelled as "swai" (its Thai
name), or "striped catfish" (formerly "sutchi catfish"). In Vietnam, this fish is known as tra. In Mexico, Grupo Piscimex markets this fish with the registered trademark "Barbero" under the brand name "Pescados y Mariscos Sierra Madre." Other than indicating the Latin name of the species on the back and that it was farm-raised in Vietnam, they make no mention of its more common names.
This fish is sometimes sold as the superior "basa
". Compared to the basa, this fish is thought to be inferior, as its meat is coarser and comes in thinner. Despite this, swai is still common, as it is much cheaper to maintain, easier to breed, and is also a faster-growing species.
s. However, they are not easy fish to keep, and are not recommended for home aquariums. Iridescent sharks are schooling fish that prefer to be kept in groups of five or more. Accustomed to living in rivers, they are very active fish that require a lot of space. They have very poor eyesight, so any foreign movement they detect outside of their habitat, they will see as an utter threat. If stressed, their first instinct is to flee, and such a blind dash can result in injuries, especially in an aquarium environment. These flights may be terminated by the fish sinking to the bottom, where it may lie on its side or back until it recovers.
Many fish owners are unaware of the enormous size an iridescent shark can reach and also that they can bite very harshly. If given enough room and fed adequately, an individual of this species can reach 1 m (3 feet) in length. In most home aquariums, the amount of space an iridescent shark has severely stunts its growth. For this reason, most iridescent sharks kept in home aquaria grow to only 15 to 30 cm (6 to 12 inches) in length and die prematurely from organ failure. As a rule of thumb, an iridescent shark requires a minimum tank size of 12 m (40 feet) to develop naturally and live a long, healthy life. Schools require even larger tanks. When provided with adequate sized aquaria and proper husbandry, an iridescent shark may live well into its teens and grow to full size.
There is also an albino morph available.
Shark catfish
The shark catfishes are a family, the Pangasiidae, of catfishes 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 Pangasianodon gigas, one of the largest known freshwater...
(family Pangasiidae) native to the rivers of Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
. It is found in the Mekong
Mekong
The Mekong is a river that runs through China, Burma, Laos, Thailand, Cambodia and Vietnam. It is the world's 10th-longest river and the 7th-longest in Asia. Its estimated length is , and it drains an area of , discharging of water annually....
basin as well as the Chao Phraya River
Chao Phraya River
The Chao Phraya is a major river in Thailand, with its low alluvial plain forming the centre of the country. It runs through Bangkok, the capital city, and then empties into the Gulf of Thailand.-Etymology:...
, and is heavily cultivated for food there. It has also been introduced into other river basins as a food source, and its striking appearance and iridescence
Iridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...
have made it common in the fishkeeping
Fishkeeping
Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...
hobby. Their omnivorous diet consists of crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, other fish, and plant matter.
Names
The fish is named for the glow or iridescenceIridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...
exhibited in juveniles, as well as the shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
-like appearance of this and other shark catfish
Shark catfish
The shark catfishes are a family, the Pangasiidae, of catfishes 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 Pangasianodon gigas, one of the largest known freshwater...
. It is also known as Siamese shark or sutchi catfish in the aquarium
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
hobby or as tra, swai , or striped catfish in the food fish market, and occasionally incorrectly as basa and panga (these names should be rather used for Pangasius bocourti and Pterogymnus laniarius, respectively).
Distribution and habitat
Iridescent sharks originate from the large riverRiver
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s Chao Phraya and Mekong
Mekong
The Mekong is a river that runs through China, Burma, Laos, Thailand, Cambodia and Vietnam. It is the world's 10th-longest river and the 7th-longest in Asia. Its estimated length is , and it drains an area of , discharging of water annually....
in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, though they have been introduced into other rivers for aquaculture. They are a freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
fish that natively live in a tropical climate and prefer water with a 6.5–7.5 pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
, a water hardness of 2.0–29.0 dGH
DGH
Degrees of general hardness is a unit of water hardness, specifically of general hardness.General hardness is a measure of the concentration of metal divalent ions such as calcium and magnesium per volume of water...
, and a temperature range of 22–26 °C (71.6–78.8 °F). 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 moves upstream to spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
during the flood season while the waters are high and returns downstream to seek rearing habitats when the river water levels recede. Upstream migration in this species appears to be triggered by receding waters. At the end of the flood season, the fish migrate back downstream away from flooded waters. 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
Khone Falls
The Khone Falls and Pha Pheng Falls is a waterfall located in Champasak Province on the Mekong River in southern Laos, near the border with Cambodia. The Khone Falls are the largest in southeast Asia and they are the main reason that the Mekong is not fully navigable into China...
, upstream migration occurs in October to February, with its peak in November to December.
Physical characteristics
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; they have a shiny, iridescent color that gives these fish their name. However, large adults are uniformly grey and lack the striping. Adults reach up to 130 cm (4 ft) in length and can weigh up to a maximum of 44.0 kg (97 lb).Food source
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
species in Thailand and Vietnam. Along with other farm-raised shark catfish
Shark catfish
The shark catfishes are a family, the Pangasiidae, of catfishes 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 Pangasianodon gigas, one of the largest known freshwater...
es, it has caused much debate within the U.S., with legislation passed recently to prevent its imports from cutting into American farmed catfish sales. Prohibited to be labelled as "catfish" in the U.S., P. hypophthalmus is now labelled as "swai" (its Thai
Thai language
Thai , also known as Central Thai and Siamese, is the national and official language of Thailand and the native language of the Thai people, Thailand's dominant ethnic group. Thai is a member of the Tai group of the Tai–Kadai language family. Historical linguists have been unable to definitively...
name), or "striped catfish" (formerly "sutchi catfish"). In Vietnam, this fish is known as tra. In Mexico, Grupo Piscimex markets this fish with the registered trademark "Barbero" under the brand name "Pescados y Mariscos Sierra Madre." Other than indicating the Latin name of the species on the back and that it was farm-raised in Vietnam, they make no mention of its more common names.
This fish is sometimes sold as the superior "basa
Basa fish
The basa fish, Pangasius bocourti, is a type of catfish in the family Pangasiidae. Basa are native to the Mekong River Delta in Vietnam and Chao Phraya basin in Thailand. These fish are important food fish with an international market. They are often labeled in North America and Australia as "basa...
". Compared to the basa, this fish is thought to be inferior, as its meat is coarser and comes in thinner. Despite this, swai is still common, as it is much cheaper to maintain, easier to breed, and is also a faster-growing species.
Culinary notes
In Vietnam, basa fish are preferred over swai because of its more delicate flake and sweeter flavor. Because consumers in Vietnam prefer basa, and since swai grows more quickly, more swai is shipped to US markets than basa.In the aquarium
Juvenile iridescent sharks are often sold as pets for home aquariumAquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
s. However, they are not easy fish to keep, and are not recommended for home aquariums. Iridescent sharks are schooling fish that prefer to be kept in groups of five or more. Accustomed to living in rivers, they are very active fish that require a lot of space. They have very poor eyesight, so any foreign movement they detect outside of their habitat, they will see as an utter threat. If stressed, their first instinct is to flee, and such a blind dash can result in injuries, especially in an aquarium environment. These flights may be terminated by the fish sinking to the bottom, where it may lie on its side or back until it recovers.
Many fish owners are unaware of the enormous size an iridescent shark can reach and also that they can bite very harshly. If given enough room and fed adequately, an individual of this species can reach 1 m (3 feet) in length. In most home aquariums, the amount of space an iridescent shark has severely stunts its growth. For this reason, most iridescent sharks kept in home aquaria grow to only 15 to 30 cm (6 to 12 inches) in length and die prematurely from organ failure. As a rule of thumb, an iridescent shark requires a minimum tank size of 12 m (40 feet) to develop naturally and live a long, healthy life. Schools require even larger tanks. When provided with adequate sized aquaria and proper husbandry, an iridescent shark may live well into its teens and grow to full size.
There is also an albino morph available.