The Mekong giant catfish, Pangasianodon gigas, is a species of catfish (order Siluriformes) in the shark catfish family (family Pangasiidae), native to the Mekong basin in Southeast Asia.

Conservation

Endemic to the lower half of the Mekong river, this catfish is in danger of extinction due to overfishing, as well as the decrease in water quality due to development and upstream damming. The current IUCN Red List for fishes classes the species as Critically Endangered; while the number of individuals living in the wild is not known, catch data indicate that the population has fallen by 80 percent in the last 14 years.
It is also listed in Appendix I of CITES, banning international trade.
In The Anthropologists' Cookbook (1977) Jessica Kuper noted the importance of the pa beuk to the Lao people and remarked, "In times gone by, this huge fish, which is found only in the Mekong, was fairly plentiful; but in the last few years the number taken annually has dwindled to forty, thirty or twenty, and perhaps in 1976 even fewer. This is sad, as it is a noble fish and a mysterious one, revered by the Lao." (p167)

Fishing for the Mekong giant catfish is illegal in the wild in Thailand, Laos, and Cambodia, but the bans appear to be ineffective, with the fish continuing to be caught in all three countries.
However, in recognition of the threat to the species, nearly 60 Thai fishermen agreed to stop catching the endangered catfish in June 2006, to mark the 60th anniversary of Bhumibol Adulyadej's ascension to the throne of Thailand.
Thailand is the only country that allows fishing for private stocks of Giant Mekongs, this is helping to save the species as the lakes purchase the small fry from the government breeding program generating extra income that allows the breeding program to function.

Fishing lakes like Bung Sam Ran in Bangkok have this species up to 140 kg, most common size landed is 18 kg although there are some companies that specialise in landing the larger fish.
These fish are non-aggressive but very powerful as they evolved in the running waters of the Mekong River where the current flow can be high at times.

The Giant Mekong can also be seen now in the Bangkok River, when feeding fish at the Bangkok temples the Giant Mekong Catfish can be seen at times the largest to date spotted has been about 25 kg.

This species needs to reach 50 – 70 kg to breed, it does not breed in lakes.
The Thailand fishery Department has been running a breeding program to re-stock the Mekong River. It is yet to be seen if the fish will spawn.

Size

Attaining an unconfirmed length of 3 m, the Mekong giant catfish grows extremely quickly, reaching a mass of 150 to 200 kg in only six years.
The largest catch recorded in Thailand since record-keeping began in 1981 was a female measuring 2.7 m (roughly 9 feet) in length and weighing 293 kg (646 lb). This specimen, caught in 2005, is widely recognized as the largest freshwater fish ever caught (although sturgeon can far exceed this size, they can be anadromous). Mekong giant catfish have been confirmed as anadromous also. Thai Fisheries officials stripped the fish of its eggs as part of a breeding programme, intending then to release it, but the fish died in captivity and was sold as food to local villagers.
Grey to white in colour and lacking stripes, the Mekong giant catfish is distinguished by the near-total lack of barbels and the absence of teeth.