Image: Giant catfish
Suthep Kritsanavarin  /  WWF International
This Mekong giant catfish was caught in Chiang Khong, Thailand, in 2005 and weighed in at 645 pounds. It was nearly nine feet long and is listed as the world's largest freshwater fish ever caught. Based on it and other giant catfish, experts estimate a fully mature male can be 10 feet long and weigh more than 700 pounds.
msnbc.com
updated 7/27/2010 7:00:38 PM ET 2010-07-27T23:00:38

Four of the world's 10 largest freshwater fish species — including a catfish that can reach 10 feet long — are threatened with extinction if hydropower dams planned on Asia's Mekong River go ahead, the World Wildlife Fund warned in a report Tuesday.

Of particular concern is the Mekong giant catfish, which is already listed as critically endangered.

"A fish the size of a Mekong giant catfish cannot swim across a large barrier (like a dam) ... to reach its spawning grounds upstream," Dekila Chungyalpa, WWF's Greater Mekong Program director, said in a statement. Such dams, he said, "will lead to the collapse of the wild population of this iconic species."

The catfish are thought to migrate from the Tonle Sap Lake in Cambodia up the Mekong River to spawn in northern Thailand and Laos, WWF said.

The three other freshwater fish species profiled in the WWF report are:

  • The Mekong giant stingray, which can be as long as half a bus. Fishermen have claimed to have seen stingrays that weigh more than 1,100 pounds, but none that large has ever been caught;
  • The so-called dog-eating catfish, given that nickname by fishermen who have caught it using dog meat as bait; and
  • The giant barb, Cambodia's national fish.

At over 600 pounds, the dog-eating catfish and the giant barb, which is part of the carp family, tie for fifth place on the global top ten, WWF said.

Image: Giant barb
Zeb Hogan  /  WWF-Canon
This giant barb was caught in 2002 on the Tonle Sap River in Cambodia, weighing in at nearly 230 pounds.

Dams would also reduce sediment flowing to the Mekong River Delta, increasing the delta's vulnerability to sea level rise, WWF added.

"The Lower Mekong is currently free-flowing but the clock is ticking," Chungyalpa said. "We have a rare opportunity to conserve these freshwater giants and ensure the livelihoods of millions of people who live along the Mekong mainstream."

Image: Giant freshwater stingray
Zeb Hogan  /  WWF-Canon
This giant stingray was seen on the Mekong near the Cambodia-Vietnam border in 2002. The disk measured 80 inches, and from tail to nose it was 163 inches long.

The Mekong originates in the Tibetan Plateau and flows to southeast Asia through Yunnan, China. It is the lifeblood for 65 million people in six countries — Cambodia, China, Laos, Thailand, Myanmar and Vietnam.

WWF said it supports sustainable dam projects on tributaries of the Mekong River and that those dams planned on the river itself should be carefully reviewed.

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