— 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:
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.
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."
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.