Thousands of catfish climb a waterfall in the Amazon
Thousands of tiny fish inching up waterfalls might sound like fantasy, but it happened in Brazil last November, reports Kristine Sabillo Guerrero.
Scientists and Brazil’s environmental police documented a “massive aggregation” of bumblebee catfish (Rhyacoglanis paranensis) in Mato Grosso do Sul’s Aquidauana River. The small blotched fish swarmed in pools at the base of waterfalls, then hauled themselves up rock faces, sometimes climbing over one another in great shoals. Some even clung upside down to the ceilings of crevices.
The spectacle, reported in the Journal of Fish Biology, marks the first recorded instance of a member of the Pseudopimelodidae family climbing waterfalls. Fully mature males and females were present, leading researchers to conclude that the catfish were likely migrating upstream to spawn. The timing coincided with the onset of the rainy season, following one of the region’s worst droughts. “It happened right after a long and severe drought in the region, and the sudden rise in water levels seems to have triggered the species to spawn,” said Manoela Marinho, the study’s lead author.
Such observations, though rare, matter. Fish migration in South America’s rivers is poorly understood, particularly for small species. The findings underscore how dams and altered water flows may disrupt not just the region’s big commercial fish, but the secret lives of its smallest ones.