Mekong dam operators urged to study fish migration
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Dam architects and operators in the Mekong River basin have been advised to conduct deep and comprehensive studies on fish migration, as different species find different ways to go through the dams.
“There might be 800 to 1,200 species in the Mekong River. In the Xayaburi dam alone, which is under construction on the mainstream of the river in Laos, there might be as many as 300 species.
“So there might be species of those fish we don’t know much about. I hope people there will work on that in detail in order to design fish ladders,” John Beeman, research fishery biologist at the US Geological Survey, said yesterday.
Beeman has experience in the lower Mekong basin covering Laos, Thailand, Cambodia and Vietnam, but was not directly involved in any studies on fish migration for any particular dam in the basin.
Designed for fish passage
Some Mekong dams such as Xayaburi, which he visited in January, were designed for fish passage through fish ladders, spillways and flushing ways for sedition and fish, he said, but declined to say whether such facilities would work well.
He is now working at the Columbia River Research Laboratory and studying fish migration and their passage through eight hydropower dams in the Columbia and Snake rivers in Washington state.
His studies of the Columbia basin found that salmon and steelhead can travel past the dams up and downstream by many routes, including bypass systems, spillways and turbines.
Young and adult salmon used different routes for their travel. The young fish swim through juvenile bypass systems, spillways and turbines to the ocean while adult salmon migrate back upstream to their spawning ground by using fish ladders.
However, salmon have a high rate of survival when they travel through dams while other species find difficulty passing through them.
“Salmon are very strong swimmers,” he said.
“Most of our successes are for salmon, but we still have challenges for non-salmon.”
The type of dam is also a key for fish passage.
Run-of-the river dams have more facilities for fish passage while high dams with reservoirs are a major obstacle for fish migration, he said.
The US Army Engineers Corps has invested more than US$1.8 billion (Bt64 billion) in improving fish passage at federal dams since 2001, resulting in significant survival improvement.
Today, major improvements have rendered these dams friendlier for juvenile and adult fish, he said.
