Plans to build a series of hydropower dams on the Mekong River could threaten already endangered species in the waterway.
The Mekong River is the lifeblood of Southeast Asia, with the largest inland fisheries in the world.
About 40 million people depend to some degree on the fisheries, worth about $2.5 billion a year.
But fisheries experts say plans by Cambodia, Laos and Thailand to build hydropower dams on the Mekong would block fish migration, threatening already endangered species.
Environmental activists say plans by Laos to build a dam in the Don Sahong area near the Cambodian border could doom the nearly extinct Irrawaddy dolphin.
Soung Ma earns money taking tourists for a rare glimpse of the dolphins. "Local people normally work in dolphin tourism. Everyone has a small boat and can pick up tourists and get money from tourists every day or every month depending on the season," Ma said.
The Mekong River Commission works to manage river resources among Cambodia, Laos, Thailand, and Vietnam.
Jeremy Bird heads the commission and says balancing the pros and cons of hydropower dams is the biggest challenge facing the Mekong basin. "We're talking about the livelihoods of millions of people but we're also talking about a huge potential resource of hydropower which can not only provide foreign revenues to the countries, but can those revenues can then be used to finance other development programs and help countries meet their targets on poverty alleviation and millenium development goals," Bird said.
Some dams on rivers feeding the Mekong have disrupted fish populations.
Fishermen may have to turn to aquaculture like this tilapia farm in Vientiane to make up for the lost wild catch.
Suchart Ingthamjitr, a program officer at the MRC's fishery program, says fish farms help meet demand. "The price of wild fish is higher than cultured fish. But, the problem of wild fish is seasonality," Ingthamjitr said. "Yeah, you can catch and have the wild fish depend on the time of year. But, for tilapia all year round you can buy it in the market."
As the sun sets on the Mekong, fishermen try their luck.
Environmental and fisheries experts say damming the Mekong will change some of their traditional ways.