A mass fish die-off in Brazil’s Amazon River region has killed an estimated 20-30 metric tons of fish and other aquatic animals, following one of the worst droughts in Amazonian history.
On the night of Nov. 12, fishers from the riverine community of Igarapé do Costa, near the city of Santarém in northern Brazil, began noticing fish dying in large numbers along the Aramanaí Channel, a waterway connected to the Amazon River and home to hundreds of fishing families.
Over the following days, the situation worsened as the channel became blanketed with dead marine animals, Manuel Pinheiro, the social and environmental director of the Z20 fishers union, which represents the impacted area, told Mongabay in an audio message.
Native fish, such as pirarucu (Arapaima gigas), one of the world’s largest freshwater fish, red-bellied pacu (Piaractus brachypomus), the talking catfish (Acanthodoras spinosissimus) and tambaqui (Colossoma macropomum) were among the affected species. Caimans, turtles and stingrays were also found dead in the fetid water. Fishermen have been transporting surviving animals to other locations.
“We have never seen anything like this,” Pinheiro said. “It’s a tragic situation. We’ve informed the environmental agencies so that they can investigate and try and identify the causes behind this disaster.” Fish die-offs are often triggered by hot weather followed by sudden rainfall, which can cause a thermal shock. “But that’s not what happened this time, it didn’t rain. We think it might be the high temperatures or the [low] oxygen levels,” Pinheiro added.
In 2024, temperatures in the Brazilian Amazon were 5.1° Celsius (9.2° Fahrenheit) higher than the historical average, according to data from Brazil’s National Institute of Meteorology. A biologist on scene reported the average water temperature was 32°C (89.6°F), while the acceptable limit for the local aquatic life would be around 28°C (82.4°F). The die-off also contaminated the channel’s water, adding strain to the families who depend on the freshwater supply.
“It’s paradoxical that riverine communities in the Amazon face water stress while living in the world’s largest freshwater basin,” Caetano Scannavino, coordinator of the nonprofit Projeto Saúde e Alegria (“Health and Joy Project”) which works in the region, told Mongabay in an audio message.
Scannavino added that the event would undoubtedly affect food security for local populations and could also disrupt next year’s fish supply. Fishers say they’re concerned about the long-term impact of the die-off. “All these fish that died also aren’t going to have offspring, so I’m worried about whether we will have fish in the future,” said Erick Penna Ribeiro, president of the Igarapé do Costa community residents’ association.