(July 27, 2010) Dams and infrastructure development along Asia’s Mekong River threaten the survival of some of the world’s largest freshwater fish species, including the giant freshwater stingray and the Mekong giant catfish, WWF said.

Hydropower dams block migration routes to spawning grounds in the Mekong, home to four of the world’s 10 largest freshwater fish species, according to a report published today by WWF, formerly the World Wildlife fund.

Populations of Mekong giant catfish, which can weigh as much as 350 kilograms (772 pounds) and are the world’s third- largest freshwater fish, have declined 90 percent in two decades, the report said. The river is also home to the largest freshwater species, the giant freshwater stingray, which can grow up to 600 kilograms.

China has completed four dams on the upper reaches of the 4,425-kilometer (2,750-mile) Mekong, the world’s 11th-longest river, and four more are planned before 2025 to provide a total capacity of 15,200 megawatts, enough to provide electricity for 75 million people. China’s first upstream dam became operational in 1993, with subsequent openings in 2003 and 2008.

Another 11 mainstream dams are in various stages of development in Laos, Thailand and Cambodia, in addition to smaller dams on the Mekong’s tributaries. More than 60 million people live in the Mekong’s lower basin, an area larger than the U.S. state of Texas.

Mainstream dams constitute “the single largest threat” to the Mekong’s wetlands, home to the world’s largest inland fishery, the Mekong River Commission said in an April 2 report.

Dry weather reduced Mekong water levels to their lowest in three decades earlier this year, raising scrutiny about management of the river as governments aim to harness its potential to provide food and generate electricity.

Stuart Biggs, Bloomberg, July 27, 2010

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