Hydroelectric dams in Brazil’s Amazonas state have slashed fished populations by as much as 90% in some locations, according to a new a study based on on-the-ground research in partnership with riverine communities. The 2008 construction of the Santo Antônio hydroelectric dam dramatically reduced the natural flow of the Madeira River, which runs through Rondônia and Amazonas states in the northwestern Brazilian Amazon. As a result, species including pirarucu (Arapaima gigas), tambaqui (Colossoma macropomum) and pirapitinga (Piaractus brachypomus) have largely disappeared from traditional fishing communities. “Fish need currents to navigate. They don’t need still water, they need moving water. And the Madeira River stopped flowing,” fisher Raimundo Nonato dos Santos, from the Lago Puruzinho community in Amazonas state, told Mongabay reporter Karla Mendes. “The impact was huge for us: the decline in fish stocks, the [milky] water remaining for many months within [the lake in] the community. It affected us a lot.” Dos Santos was one of more than a hundred fishers who collaborated with researchers from the Federal University of Amazonas on the 2023 study. They analyzed daily catch data between 2009 and 2010, before the dam was completed, and again between 2018 and 2019, after it was finished. They found a dramatic drop in the number of fish caught in the region following the dam. “The results show that the installation of the hydropower plants negatively affected the capture dynamics of several fish species by changing the capture periods and spots previously recorded,” the study’s authors wrote. In…This article was originally published on Mongabay

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