Already under attack by overfishing, pollution and deforestation, Tonle Sap Lake fisheries face an even bigger threat in the form of hydropower dams, according to experts.

Laos’ planned Don Sahong Hydropower Project in particular has environmentalists fearing an emptier, less bio-diverse lake, and a nation pitched into protein shortages.

“[The Don Sahong] is of particular concern because it will obstruct the only fish migration channel available at Khone Falls in the dry season,” said Eric Baran, director of the World Fish Centre’s Greater Mekong Office.

At least 32 fish species are known to migrate between the Tonle Sap Lake and the Upper Mekong through the Khone Falls, just north of the Laos-Cambodian Border where the Don Sahong would be built, according to fish experts.

“I view it like a declaration of war by Laos on Cambodia and Vietnam,” said ecologist Taber Hand. “The impact of reducing fisheries and sediment flow is more subtle than most acts of war but it has the same or greater . . . effect on national security.”

Millions of people rely on fish from Cambodia’s great lake as a source of income and food security. Scientists estimate between 60-70 per cent of the nation’s fish catches come from the lake, providing Cambodian’s main source of protein and omega-3 fats.

“One hundred per cent of the Cambodian population eats fish. We have no alternatives to completely replace fish as a source of protein right now,” said Meach Mean, director of the 3S Rivers Protection Network.

Dam opponents have gone so far as to say deleterious impacts on Tonle Sap Lake fisheries would mean several steps backwards in alleviating the nation’s poverty and malnutrition rates.

“No dams should be built until Cambodian’s food security can be guaranteed,” said Tek Vannara, executive director of NGO Forum.

But Don Sahong proponents maintain that if alternative fish migration routes fail, the project could be halted.

“The Don Sahong dam is a very expensive project. I don’t believe for a minute that the dam would be stopped after such an investment if it turned out that impacts on fish migrations could not be mitigated appropriately,” said Ian Baird, a professor and fisheries expert at the University of Wisconsin-Madison.