CHHAING CHOMRAS, CAMBODIA - At the local fish market here along the banks of the Tonle Sap, the morning harvest is enormous. Prized catfish, among other species, dominate sales as buyers for restaurants pile in for the biggest and best on offer.

Early business is brisk for the fish farmers who bred and reared their fish securely in ponds. But the afternoons are different, said Man Mat, a 29-year-old fish monger.

That's when local fishermen deliver their daily catch, taken from near here and the nearby Mekong River. Their yields, however, are paltry and Man Mat blames a range of issues for the dwindling fish stocks, including illegal fishing with electric nets, overfishing, climate change and drought.

But he says the greatest problem confronting his business is the multi-billion dollar dam construction program in Laos.

“The fish are getting smaller and smaller,” said Man Mat, a Muslim Cham and son of a fisherman. “My father catches 5-to-15 kilograms a day when before it was 100 to 200 kilograms...in 10 years, there'll be no more fish left.”

His sentiments are being echoed across the Mekong Delta, where the damming of the Mekong River and destruction of a natural habitat that allows fish to migrate upstream to spawn has upset those who ply these waters for their livelihoods.

Start of the problem

It began with a decision by Vientiane to press ahead with the $3.8 billion Xayaburi dam in 2012 despite a public outcry from scientists and environmentalists. Authorities then announced they would also proceed with the $300 million Don Sahong Dam at Siphandone, home to the endangered Irrawaddy Dolphin and the famed 4,000 Islands.

But the final straw for many was last month's decision by the government of Lao President Bounnhang Vorachith to proceed with a third $1.88 billion dam across the mainstream at Pak Beng in the country's north, as part of a broader strategy to sell electricity into neighboring countries, especially China, which has built its own dams across the Mekong in its territory.

“They keep the fish in the upper reaches of the river and they only release them when the water levels are high,” Man Mat said. “Now fish numbers are really down.”

The total fish harvest from the Mekong River and its lower delta was valued at $11 billion a year in 2015, according to the fisheries research and development newsletter "Catch and Culture."

Major industry

About 70 million people depend on those fish. Their food security has emerged as a major issue confronting the Cambodian and Vietnamese governments.

Over the last two decades, the population living off the Mekong in the downstream delta region has increased by at least 10 million people, upping the demand for fish and leading to a phenomena scientists call “fishing down,” which results in the depletion of large fish that are then replaced by once discarded smaller fish.

“Laos should stop the dams because they are having a big impact on fishing,” said Ra Thuy, a 41-year-old fisherman who also plies these waters with a sampan and net. “The dams are stopping the fish from traveling upstream to spawn”.

He says fishing is currently not good due to lower-than-usual water levels. “At the moment I'm not fishing, just fixing the boat,” he said.

Fishermen like Ray Thuy and Outh Hien, 69, echoe Man Mat’s concerns. Both say they used to catch up to 300 kilograms of fish a day, but this had dropped to around 20 kilograms, and that's on a good day.

“Five times I flung my net this morning and this is all I got,” Outh Hien said, pointing to his grandchildren and holding up his paltry morning catch of little fish, enough perhaps to bait a hook.

“I have also heard Laos is building a third dam across the Mekong River,” he said. “That's it for me – no fish, my grandchildren will do something else as they can only go to school”.

'Battery of Asia'

But Vientiane is unmoved. It plans to sell hydro-electricity into neighboring countries through the eventual construction of 11 dams across the Mekong River, and another 123 across the country, in its quest to turn the isolated and impoverished state into “the battery of Asia.”

Laos has also tried to allay concerns over fish breeding by arguing fish by-passes would be built to enable fish migration patterns to continue upstream for spawning. However, scientists are far from convinced that by-passes will work, citing a lack of evidence.

This is creating a heavier dependence on farmed fish.

According to "Catch and Culture" growth rates, aquaculture growth in the Mekong River Basin is three times faster than the global average. It also valued contributions from fish farms at about $5.8 billion in 2015, up from $4.8 billion in 2010. It was less than $1 billion in 2003.

And that's being reflected here at the local fish market in Chhaing Chomras, where aquaculture is flourishing while traditional fishermen struggle.