Mekong giant catfish

Mekong giant catfish
Conservation status
Critically Endangered (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Siluriformes
Family:	Pangasiidae
Genus:	Pangasianodon Chevey, 1931
Species:	P. gigas
Binomial name
Pangasianodon gigas Chevey, 1931
Synonyms
Pangasius paucidens Fang & Chaux, 1949

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

Species characteristics

The Mekong giant catfish is perhaps the most interesting and most threatened species in the Mekong river. For this reason conservationists have chosen it as a sort of “flagship” species to promote conservation on the Mekong.^[1] With recorded sizes of up to 10.5ft (3.2m) and 660lb (300kg), the Mekong’s giant catfish currently holds the Guinness Book of World Record’s position for the world’s largest freshwater fish.^[2] Although research projects are currently ongoing, relatively little is known about this species. Historically, the fish had a natural range that reached from the lower Mekong in Vietnam (above the tidally influenced brackish water of the river’s delta) all the way to the northern reaches of the river in the Yunnan province of China, spanning almost the entire 4,800 km length of the river.^[3] Due to threats, this species no longer inhabits the majority of its original habitat; it is now believed to only exist in small, isolated populations in the middle Mekong region.^[4] Fish congregate during the beginning of the rainy season and migrate upstream to spawn.^[4] They live primarily in the main channel of the river, where the water depth is over 10m^[5] while researchers, fishermen and officials have found this species in the Tonle Sap river and lake in Cambodia, a UNESCO Biosphere reserve. In the past, fishermen have reported the fish in a number of the Mekong’s tributaries; today, however, essentially no sightings are reported outside of the main Mekong river channel and the Tonle Sap region.

In infancy, this species feeds on zooplankton in the river and is known to be cannibalistic.^[6] After approximately one year, the fish becomes herbivorous, feeding on filamentous algae, probably ingesting larvae and periphyton accidentally.^[7] The fish likely obtains its food from algae growing on submerged rocky surfaces, as it does not have any sort of dentition.^[6]

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 by the People's Republic of China. The current IUCN Red List for fishes classes the species as Critically Endangered; the number living in the wild is unknown, but catch data indicate the population has fallen by 80 percent in the last 14 years.^[8][9] It is also listed in Appendix I of CITES, banning international trade.^[10]

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."^[11]

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.^[8]

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.^[12]

Thailand is the only country that allows fishing for private stocks of Mekong giant catfish. This helps save the species as 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 the species up to 140 kg;. The most common size landed is 18 kg, although there are some companies that specialise in landing the larger fish.

The fish are not 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 Mekong giant catfish can also be seen occasionally in the Chao Phaya River. When feeding fish at the Bangkok temples along the river, the fish will be seen at times. The largest spotted to date has been about 25 kg.

The species needs to reach 50 to 70 kg to breed, and unfortunately it does not breed in lakes.

The Thailand Fishery Department has instituted a breeding program to restock the Mekong River. However, 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.^[13] 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). 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.^[14][15][16]

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.^[13]

References

1. ^ (Hogan et al. 2004, MGCCG, 2005)
2. ^ (Mydans et al. 2005, Hogan et al. 2004, Hogan et al. 2007)
3. ^ (Lopez et al. 2007, Hogan et al. 2007)
4. ^ ^{a b} (Hogan et al. 2004)
5. ^ (Mattson et al. 2002),
6. ^ ^{a b} (Pholprasith, 1983 as cited in Mattson et al. 2002)
7. ^ (Pookaswan, 1989 and Jensen, 1997 as cited in Mattson et al. 2002)
8. ^ ^{a b} Hogan (2003). Pangasianodon gigas. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 9 May 2006.
9. ^ "Giant Catfish Critically Endangered, Group Says". National Geographic News. 2003-11-18. http://news.nationalgeographic.com/news/2003/11/1118_031118_giantcatfish.html. Retrieved 2006-06-29. 
10. ^ "CITES Appendices I, II and III". CITES. 2006-06-14. http://www.cites.org/eng/app/appendices.shtml. Retrieved 2006-06-29. 
11. ^ (p167)
12. ^ "Giant Mekong catfish off the hook". BBC News. 2006-06-10. http://news.bbc.co.uk/2/hi/asia-pacific/5068206.stm. Retrieved 2006-06-29. 
13. ^ ^{a b} Froese, Rainer, and Daniel Pauly, eds. (2006). "Pangasianodon gigas" in FishBase. March 2006 version.
14. ^ "Grizzly Bear-Size Catfish Caught in Thailand". National Geographic News. 2005-06-29. http://news.nationalgeographic.com/news/2005/06/0629_050629_giantcatfish.html. Retrieved 2006-06-29. 
15. ^ "Fish whopper: 646 pounds a freshwater record". 2005-07-01. http://msnbc.msn.com/id/8404622/. Retrieved 2006-06-29. 
16. ^ Mydans, Seth (2005-08-25). "Hunt for the big fish becomes a race". International Herald Tribune. http://www.iht.com/bin/print_ipub.php?file=/articles/2005/08/24/news/fish.php. Retrieved 2006-06-29. 

External links

• Photographs of sport fishers with their catch
• Photo in National Geographic of a large specimen