Iridescent shark
The iridescent shark (Pangasius hypophthalmus) 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 crustaceans, other fish, and plant matter.
The fish is named after the glow or iridescence exhibited in juveniles, as well as the shark-like appearance of this and other shark catfish. It is also known as tra, swai (from Thai ปลาสวาย "plaa sawaaj"), 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). However in Spain, it is known as panga.
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. 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. In the USA it is known as swai. In the UK it simply sold under the name Pangasius and is available from many Asian shops.
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, the iridescent shark is still common as it is much cheaper to maintain, easier to breed, and is also a faster-growing species. It is said that 90% of fish sold as basa is actually iridescent shark.
Reference: CC-BY-SA