- Having fishers as protagonists, a recent study disclosed unanswered details about the Amazon communities and fish species most affected by two Madeira River dams.
- The dams limited the natural flow of the Madeira, disrupting the currents that fish need and causing up to a 90% reduction in stocks in some locations; species like pirarucu and tambaqui have largely disappeared from traditional fishing communities.
- The research serves as evidence to support the decade-long legal battle by fishers in Humaitá who are seeking compensation for losses caused by power plants.
LAGO PURUZINHO, Brazil — Looking at the clear waters of Puruzinho Lake, fisher Raimundo Nonato dos Santos regrets the decline in fish stocks affecting the livelihood of his community in the Brazilian Amazon.Species like pirarucu (Arapaima gigas), tambaqui (Colossoma macropomum) and pirapitinga (Piaractus brachypomus) have “disappeared” from Lago Puruzinho community in northern Amazonas state, dos Santos said. “When we catch one, it’s a surprise.”
A resident of Puruzinho since he was born 53 years ago, dos Santos, leader of the Puruzinho community and known by his nickname Leleca, said the construction of the Santo Antônio hydroelectric power plant in neighboring Rondônia state in 2008 “triggered the ruin” of his community.
Often promoted as a form of “clean energy” since they don’t run on fossil fuels, hydropower plants have shown severe environmental impacts. Brazil’s fifth-largest power dam, Santo Antônio sparked outcry from environmentalists since the start of its construction on the Madeira River due to its environmental and social impacts, including a reduction in fish stocks and the displacement of traditional communities. Its reservoir spans more than 54,600 hectares (135,000 acres), limiting the natural flow of the Madeira.
“Things started to spiral out of control. And 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 told Mongabay under a tall tree on the banks of Puruzinho Lake, 20 kilometers (12.4 miles) away from the city of Humaitá.
As the plant started operations in 2012, the scarcity of fish was already affecting not only catches and sales for fishers but also the diet of the Puruzinho community, which traditionally ate fish “every day,” dos Santos said. “Fish need currents to navigate. They don’t need still water, they need moving water. And the Madeira River stopped flowing.”
The Madeira was also affected by the Jirau hydropower plant, the country’s fourth-largest, 120 km (74.5 mi) upstream, which began operating in 2013.
Since then, a wide range of studies have shown a reduction in fish stocks following the infrastructure projects along the Madeira. A recent paper disclosed details about the most impacted communities and species — unanswered questions until then — having fishers as protagonists.
Dos Santos was one of 120 fishers who worked with the researchers, providing them with “invaluable information about the region,” said co-author Igor Hister Lourenço, a former researcher at the Laboratory of Ichthyology and Fisheries Management of the Madeira River Valley at the Federal University of Amazonas (UFAM). “Unfortunately, he is one of the people who have been affected by the decline in fish stocks — and he is also one of the biggest contributors to the research.”
Published in November 2023, the paper, led by UFAM, analyzed data from daily catches brought to the Humaitá Fishing Colony between May 2018 and April 2019 — updated data are underway — and information from the period prior to the Santo Antônio dam in 2009 and 2010 collected by the Federal University of Rondônia. “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 found.
These findings were only possible, Lourenço said, thanks to collaborative work between fishers and researchers using the TSBCAMPA method (Low-Cost Social Technology Applied to Artisanal Fisheries Monitoring), proposed by him and other researchers.
Disappearing catches
On their way back from a day of fishing, fishermen shared information on where, how, when and how much they spent to catch fish as well as the amount and the species caught, he added. UFAM laboratory technicians present at the daily landings write this information in a form to quantify and identify the fish and take biometric measurements and photos of all captured fish, he continued. Later, all this information and photos are systematized, allowing researchers to identify which fish came from which vessel, which fisher caught them and what species each is, Lourenço added.
“Puruzinho was one of the areas with the most fish in the municipality,” Lourenço told Mongabay on the banks of the Madeira, inside a boat used for the research and serving as his home. “It is a fact that catches have decreased,” he added, while an alligator rested on the riverbank and a green iguana (Iguana iguana) climbed trees.
The study pointed to 25 new fishing grounds “with expressive captures,” while catches disappeared in the communities of Sossego, Trapicho, Lago do Caiarí and Santa Júlia, “leading fishermen to look for new and more distant fishing areas in different times of the year.” The paper also recorded fewer catches of Characiformes and Siluriformes, orders that encompass several families, genera and species of scaled and non-scaled fish; for the latter, it also started to be captured in different locations and periods.
“Consequently, it led the fishermen to look for new and more distant capture sites and occasioned the disappearance of communities that historically explored areas no longer productive, reflecting the effects of the damming over the spatial/temporal capture gradients.”
The research also showed a reduction of up to 90% in fish stocks in some locations, among 65 species caught in the areas of influence of the Santo Antônio and Jirau dams. But Lourenço said, “The biggest problem is not even the reduction in catches — despite the fact that this is something that exists and it is corroborated by fishermen’s reports.” For him, the main issue is the changes in the spatial-temporal dynamics in small-scale fishing activities. “What does that mean? Some species are now being caught in different places and at different times, which leaves some communities extremely affected.”
According to Lourenço, the data on the reduction of fish in the study is somewhat “debatable” because different methods were used in the periods pre- and post-dams, making it difficult to carry out an exact comparison. In previous studies, he added, the findings were generic in terms of information on the most impacted communities and species following the Madeira dams. The same happened with information shared by the companies, which did not disclose the place of capture or the specific species, only the common name and total catches, he added.
In an emailed statement, Axia, responsible for the Santo Antônio dam, said the plant has been operating “sustainably” and conducting social and environmental actions supervised by government authorities and “in dialogue with surrounding communities and civil society representatives.”
The company said it invested more than 2.6 billion reais ($471 million) to carry out 28 social and environmental programs, including an ichthyofauna program that has been monitoring fish population dynamics since 2009 and a fish transposition system, but it didn’t disclose the results. Axia said Santo Antônio has a small reservoir that “reproduces the hydrological behavior” of the Madeira and “does not interfere with the natural force of the river.”
Jirau Energia, owner of the Jirau dam, didn’t respond to Mongabay’s requests for comment.
Aiming to solve this problem through a more “refined survey,” Lourenço said teaming up with fishers was key: A few species were selected, allowing the evaluation of their catches before and after the dam in specific locations.
Fewer fish everywhere
“After the power plants, the fish disappeared,” smallholder Maria Delci Barros de Morais, 58, told Mongabay on the balcony of her house in Paraíso Grande, a community also covered by the 2023 research.
A resident of the community for 37 years, Morais said fish were very abundant, but now they can’t make a living from it. “My sons spend money on fishing nets, on Styrofoam, on ice, and sometimes they don’t even make enough for subsistence, let alone to sell and to cover their costs.”
In Rondônia state, Mongabay also visited the Calama riverside community and the Karipuna Indigenous Territory, both in the area of influence of the dams but not covered by the study. Complaints about the scarcity of fish are widespread.
“Ten years ago, in half an hour, you could catch, without exaggeration, up to 500 kilograms [1,100 pounds] of fish,” Indigenous leader Adriano Karipuna told Mongabay beneath the ancient trees of the Amazon Rainforest in the Karipuna territory. “Today, we spend six hours fishing, and if we catch four fish, that’s a lot. And it’s not the right size of fish.”
Maria das Graças Correia da Silva, who works as an assistant and cleaner at a local school, said fish stocks reduced drastically after the dams. She said she likes to eat wild-caught fish every day, but the only way to eat fish amid scarcity is buying farmed fish in the state capital, Porto Velho, she added. “It was a while without eating fish from the region.”
All communities also reported losses from floods after the dams, as well as more health issues after having to replace fish with other sources of protein, especially chicken and processed food.
Lourenço said the companies told researchers the decline in fish stocks is due to overfishing, which he said is not true because researchers monitored landings. According to him, the companies also said the dams “do not affect the overall average for the basin,” which is true, but the difference in water levels — hydropeaking or repiquete in Portuguese — causes losses to fishermen.
“Fish don’t understand [these changes in water levels]; what they understand is the volume of sediment in the water and the water level. So, when the river rises, they go to the tributaries, and when it falls, they return,” said Lourenço, currently a research and development analyst at Mamirauá Institute for Sustainable Development. “Fishermen have historically had this knowledge, passed down through generations, knowing when and where to fish. Now, they go out, set their nets, and then the river rises when the fish should be going downstream. And that’s harmful because it involves investment, it’s expensive.”
Fighting for compensation
Since 2013, fishers from Humaitá have been seeking compensation for fishing losses from the companies that own the power plants. Backed by studies attributing negative impacts to dams, they filed a lawsuit seeking compensation for moral and property damages, but a judge in Humaitá ruled that the claim had surpassed the statute of limitations. Fishers appealed to a higher court, and the case is pending a decision.
Lourenço, the researcher, said the 2023 study is a snapshot from 2018 to 2019, but the situation may have changed even more. The collection of all this information is continuous work, he added, and updated data are in the process of being published, which will allow the researchers to “compare our data with our data” and have less uncertainty about the results.
Data collected by UFAM researchers since 2018 are available through an interactive dashboard, aiming to help manage fish stocks and support policies for fisheries management and the conservation of the aquatic ecosystem, Lourenço added. The tool provides detailed information for species caught in the region, including location, weight, size, price per kilo and hydrologic periods.
To encourage fishers to collaborate with the study, Lourenço said, they were granted the right to use the data to report their retirement claims, given that small-scale fishing is usually an informal job.
But the main goal of the initiative is to help them get compensation for the damages, he added. “Our ultimate dream is that in the future they will be able to fill out this form themselves, but currently we need technicians, the laboratory researchers who are there every morning at the landings,” he said.
In Puruzinho Lake, dos Santos said his dream is to raise fish in the region to fight the decline in stocks. He said he needs funds to clear the association’s debts and move forward with buying fish tanks.
“When we talk about fish, it provides income, ensures our survival and feeds us. Fish is very important to us in our region.”
Banner image: On their way back from a day of fishing, fishers shared information on where, how, when and how much they spent to catch fish as well as the amount and the species caught. Researchers present at the daily landings collect information to quantify and identify the fish, take biometric measurements and photos of all captured fish, and systematize the data, allowing researchers to identify which fish came from which vessel. Image courtesy of Igor Hister Lourenço.
Karla Mendes is a staff investigative and feature reporter for Mongabay in Brazil and the first Brazilian to win the John B. Oakes Award for Distinguished Environmental Journalism. Member of the Pulitzer Center’s Rainforest Investigations Network, she is also the first Brazilian and Latin American ever elected to the board of the Society of Environmental Journalists (SEJ); she was also nominated Diversity, Equity and Inclusion (DEI) chair. Read her stories published on Mongabay here. Find her on 𝕏, Instagram, LinkedIn, Threads and Bluesky.
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