Mekong Giant Catfish: Freshwater Species of the Week

picture of a mekong giant catfish
Three men capture a 591-pound, 5-foot-long Mekong Giant Catfish from the Tonle Sap River in Cambodia. Photograph courtesy of Zeb Hogan


freshwater species of the weekMany of the biggest names in conservation are set to meet September 6-15 on picturesque Jeju Island off South Korea for the 2012 IUCN World Conservation Congress. To kick off that event IUCN is launching a new report this week called The Status and Distribution of Freshwater Biodiversity in Indo-Burma.

The IUCN report is the first ever detailed biodiversity survey of the Mekong River between Luang Prabang and Vientiane, and it includes the controversial Xayaburi dam site, a Thai-built project in Laos that National Geographic has covered previously.

Radio Australia reports that IUCN found that “while it is still relatively healthy, the Xayaburi and other dams planned for the Mekong could cause a dramatic deterioration in biodiversity in the near future.”

At risk may be the Mekong giant catfish (Pangasianodon gigas), a mammoth but poorly understood beast that is often called the world’s biggest freshwater fish. Capable of reaching 10 feet (3 meters) in length and 650 pounds (295 kilograms), Mekong giant catfish live mainly in the lower half of the Mekong River system in Cambodia, Laos, Thailand, and Vietnam.

The giant catfish were once relatively common in the biodiverse region, but overfishing and blocking of the rivers by dams have taken a heavy toll, especially since the species prefer to migrate long distances to spawn. The population has plummeted more than 95 percent and is now considered highly endangered. Biologists worry that additional dams could make the situation worse.

Mekong giant catfish are toothless herbivores. Adult Mekong catfish have reduced barbels (“whiskers”) that are more prominent in youngsters.

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Picture of a mekong giant catfish
A Khmer man travels with a 353-pound, 8-foot-long Mekong giant catfish (Pangasianodon gigas) on the Tonle Sap River in Cambodia. Photograph courtesy of Zeb Hogan.


Brian Clark Howard covers the environment for National Geographic. He previously served as an editor for and E/The Environmental Magazine, and has written for,,, Yahoo!, MSN, Miller-McCune and elsewhere. He is the co-author of six books, including Geothermal HVACGreen LightingBuild Your Own Small Wind Power System, and Rock Your Ugly Christmas Sweater.