Giant catfish  (Pangasianodon gigas)

The giant catfish is the world's largest freshwater fish (1). It has a whitish underside and the back and fins are grey. The eyes are located low on the head and point downwards. Whilst juveniles have barbels, adults can be distinguished from other large catfish by their reduced barbels and lack of teeth (4).

The giant catfish is endemic to the parts of the Mekong River basin that run through Cambodia, Laos, Thailand, Viet Nam and possibly Burma and China. It is primarily found in the Tonle Sap River, the Tonle Sap Lake and the Mekong River (1).

Inhabits freshwater rivers and lakes (1).

A migratory species, the giant catfish is thought to move from the Tonle Sap Lake in Cambodia from October to December each year and into the Mekong River from which it progresses upstream into northeastern Cambodia, Laos or Thailand to spawn (1).

The giant catfish eats the vegetation growing on the river bed (3).

The giant catfish has been subject to over-fishing for many years. Catches at the beginning of the 20th century were in the thousands each year but declines have been so severe that less than ten are now caught per year (1). Habitat loss and degradation as a result of damming and the clearance of flooded forest near the Tonle Sap Lake (1) have disrupted the giant catfish's migration, spawning, eating and breeding habits (5).

The giant catfish has been listed on Appendix I of the Convention on International Trade in Endangered Species since 1975 when it first became apparent that it had seriously declined. It occurs in a Biosphere Reserve and a RAMSAR site (for wetlands of international significance), but both fail to provide active protection. In Cambodia and Thailand it is illegal to catch the giant catfish but this legislation is not enforced. In Laos it is protected, but again, this has no practical effect (1).

Artificially spawned individuals have been released into the River Mekong since 1985, and captive breeding has been taking place since 2001 (1). The Mekong Fish Conservation Project works in cooperation with the Cambodian Department of Fisheries to conduct research and educate the public. This project has released 20 catfish into the river system since 2000 (5). Studies have provided evidence that it spawns in areas that will be impacted by the Mekong Navigation Improvement Project which plans to dredge long stretches of river and blast away areas with rapids that obstruct the passage of large ships. The project was partially underway before the reliability of the Environmental Impact Report was questioned, and the project was put on hold (6).

For further information on this species see National Geographic:
http://news.nationalgeographic.com/news/2003/11/1118_031118_giantcatfish.html

For further information on the Mekong River see the ASEAN Regional Centre for Biodiversity Conservation's Mekong River description:
http://www.arcbc.org.ph/arcbcweb/wetlands/lao_PDR/lao_mekriv.htm

and the Australian Mekong Resource Centre website:
http://www.mekong.es.usyd.edu.au/case_studies/rbm/home.html

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk