Fishermen: Dams, Illegal Fishing, Climate Change Cause Fish Decline on the Upper Mekong

A man throws out a fishing net from his boat on the Mekong River. Photo: Mekong River Commission

Fishermen concern over dwindling fish catch

STUNG TRENG – Some fishermen in Stung Treng province expressed their concerns over the year on year decrease in catches caused by illegal fishing, climate change and upstream dam construction on the Mekong River.

The upper Mekong River in Stung Treng province is considered to be a safe haven for the reproduction of fish, especially for rare fish species. However, climate change, illegal fishing, deforestation, flooding, low river flows, dam construction, water pollution and other contributing factors are threatening the Mekong's fish stocks.

Livelihoods of Stung Treng fishermen living along the river are affected by dwindling fish catch.

San Mao, a life-long resident of Thala Parivat district, Stung Treng province, is a fisherman and a tourist driver in the Borei O’Svay ecotourism community. He said he noticed a drastic change in fish catches in the past years, adding that he sometimes cannot even catch a single fish.

San Mao, a life-long resident of Thala Parivat district, Stung Treng province.
San Mao, a life-long resident of Thala Parivat district, Stung Treng province.

“Ten or 20 years ago, I could catch 10 to 20 kilograms of fish per day during the fishing season. But now, even though it is the fishing season, I cannot catch even three kilograms,” he said.

Irregular river flow conditions are a threat to fisheries. “In the past 10 years, the water has not been following the same patterns as before. The water level fluctuates regardless of the season, so fishing is not the same as it used to be,” said the fisherman.

In addition to the problem of stream water changes affecting fish habitats and spawning, Mao sees illegal fishing and off-season fishing–during fish spawning season–as another driving force behind fish extinction.

Around 30 kilometers South, Vat Samnang, another fisherman, also complains about declining fisheries due to irregular river changes.

Living in Koh Snaeng commune, Stung Treng province, and working as a tourist driver in Samros Koh Han ecotourism community, Samnang has been a fisherman since the age of 10.

To the 42-year-old fisherman, “fishing now and in the past is very different. With one or two throws of a cast net, I cannot even catch even one or two kilos of fish these days.” “It is really scarce!” he said, adding that he is worried about the fish scarcity, but has no solution to the problem aside from fishing as usual.

Bun Samphan, president of Koh Han Community Based Ecotourism, thinks the construction of dams is an element contributing to the decrease of fish production. Inconsistent water level affects not only the fishery but also the crops of the community.

“Dam construction is depleting fish” she said, “Before, even during periods of unstable water, there were fish in the river. Now, water is more unstable and fish disappear.” The construction causes rising and falling water level, leading to gradual collapse of trees along the river and affects the habitat and spawning of the fish.

Heng Kong, director of the National Aquaculture Research and Development Institute, Fisheries Administration, sees a decline in freshwater fishery yields.

“I have interviewed fishermen in the seven or eight communities of the Ramsar Sites [areas designated as Wetlands of International Importance, Cambodia currently has five of them]. Most of them said fish are declining because of the dam that alters natural flows of water regime,” he said.

Illegal fishing remains a problem due to the vast areas Ramsar sites cover and the inadequacy of district police force available to monitor. But the construction of hydropower dams upstream is also a major issue that threatens the biodiversity of the Mekong River, citing the water regime change in the Ramsar site in Cambodia due to the operation of the Don Sahong dam in Lao.

The Stung Treng Ramsar site, which is a 40-kilometer stretch of the northern part of the Mekong in Cambodia, was considered to be a deep canyon for fish during the spawning season. But it has become incrementally shallower as a result of dams and sand pouring into the area, Heng Kong claimed.

According to a report by Cambodia's Fisheries Administration, the total output of freshwater fisheries over the last three years has declined significantly. The fish catch in 2020 was 413,200 tons, down 13.71 percent compared to 2019. And the fish catch further declined by 7.3 percent in 2021. In 2021, Cambodian authorities cracked down on 2,952 fishing crime cases, a slight increase of 28 cases, compared to the crackdown in 2020, which was 2,923 cases.

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