This is the second in a series of stories exploring the importance of the Mekong River in China.

The smell of the fish market in Jinglin hits you long before it comes into sight. Tiny shrimp and whitefish are hung up to dry here, and husband-and-wife fishing teams heft baskets brimming with freshly caught fish onto digital scales. “This has only been possible since the dam,” 44-year-old fisherman Su Youdong said, gesturing to the fish market.

Jinglin, in southwestern China’s Yunnan province, is one of the few towns along the upper stretch of the Mekong where fishing is possible. For the most part, the river, known as the Lancang in Chinese, snakes its way through steep gorges with a force and speed that would make it impossible to navigate. Upstream from Jinglin is one of Yunnan’s 14 dams along the Mekong. Each dam has dramatically changed the river, the surrounding landscape, and the livelihood of the people who live there.

The dams have harnessed the river’s power and slowed it down so much that it can now be navigated by boat in places like Jinglin. Two or three hours on the water is enough time to catch 30 kilograms of fish, with a kilogram fetching around 24 yuan at the market, Su explained. In just a few hours of work, the fisherman, mostly former farmers, can make as much as $100 a day. For the residents of Jinglin, the dam has been a blessing.

Searching for a greener energy alternative to coal, China has built 22,000 large dams, according to the World Commission on Dams. Prior to 1949, it had just 22. “China has been building hydropower for a long time, and most of the rivers are now completely blocked because of all the dams and all the development that’s happened,” Stephanie Jensen-Cormier, China program director at International Rivers, an advocacy group, told Sixth Tone.

Rich in rivers, Yunnan has a hydropower capacity in excess of 50 gigawatts. Just over a decade ago, that figure was 10 percent of today’s. China said it is building dams because they don’t pollute the air, are safe, and help with flood control and droughts — and yet experts warn of the development of dams because of the impact they have on rivers. “Rivers are the arteries of the planet,” Jensen-Cormier said. “It’s important to keep rivers flowing and healthy, and having development that negatively impacts them, it’s not good for the health of the planet.”

Downstream, in Laos, Thailand, Cambodia, and Vietnam, an estimated 60 million people depend on the Mekong as a main source of drinking water, irrigation, and even transportation. Fishing is often their only way to make a living, and to put protein on the table.

With each new dam, local residents must be relocated to make way for the massive reservoir. For the Three Gorges — the world’s largest dam, located on the Yangtze River — around 1.3 million people had to be relocated. Today, their old homes and farmland lie at the bottom of a 1,000-square-kilometer lake. (Estimates for the number of displaced residents range from as low as 1.2 million to as high as 1.5 million.)

Additional concerns are fish populations and biodiversity. Because the Mekong runs 4,350 kilometers through several different climate zones, from the freezing Himalayan Plateau to humid, tropical Southeast Asia, its biodiversity is second only to the Amazon. More than 1,100 fish species live in the river, including the giant freshwater stingray, which can weigh up to 600 kilograms, and the rare Irrawaddy dolphin. New species not previously known to humanity are discovered every year.

But dams often block fish from migrating up- and downstream, making it impossible for many to return to their spawning grounds and lay eggs. Though “fish ladders” have been used to help fish get over the dams by jumping upwards through a series of pools, scientists have said that these mitigation efforts are far from effective. At a dam on the Connecticut River in the U.S., for example, 300,000 to 500,000 fish are supposed to pass through each year, but the actual number of successful migrants is only around 700 per year. Other dams using fish ladders and elevators have reported similar results.

It’s difficult to scientifically assess the impact of dams on aquatic ecosystems. “But with 14 large dams of many, many megawatts, it’s obvious that there would be an impact on fish populations,” Jensen-Cormier said.

While fishing in the lower reaches of the Mekong has been passed on from generation to generation, Su and the other residents have only swapped their spades and pitchforks for fishing nets in the last five years. Since then, they have started to notice a change. “The rare and expensive species are gone — now I catch mostly common species, like tilapia and carp,” Su said, nudging the outboard motor to maneuver around unseen nets just below the surface of the water. “It’s gotten harder. More and more people are fishing, so we get less. When fishing first started, there were not many people doing it. Now, there are lots.”

As Su’s boat winds through the Mekong, there seem to be fishing vessels around every bend. But if there is any animosity between fishermen over the dwindling species diversity, they do not express it. Instead, they call out to each other cheerfully and chat in passing about the quality and quantity of their catches.

Huang Daoming is the deputy chief engineer at the Institute of Hydroecology of the Chinese Academy of Sciences in Wuhan, and he is all too familiar with situations like this. “Overfishing is an important reason for the decrease in China’s fish resources, and the Lancang River is no exception,” he said. With the large reservoirs and slower current created by dams, fishing is bound to grow — at least initially. “The changes will undoubtedly improve the fishing situation, [but] developing a stable industry depends on fishing at a reasonable frequency,” Huang added.

So many fish are now being caught in Jinglin that tourists from nearby have started to come here simply to enjoy relaxing fishing trips on the weekends.

With more and more human activity in the reservoir, Su now has 10 nets, each spread out in a different spot. He checks them every day. Along the main bridge that spans the river, the former farmers hang their fish out to dry.

This story was published in collaboration with A River’s Tail, a yearlong exploration of the Mekong from the river’s delta in Vietnam to its source in the Tibetan Plateau. For more stories from the Mekong, visit www.ariverstail.com.

(Header image: A fisherman pulls in his net on a tributary of the Mekong River in Jinglin, Yunnan province, Feb. 4, 2016. Luc Forsyth for Sixth Tone)