Watch These Rock-Climbing Fish Scale a 50-Foot Waterfall in the Congo Basin, the First Known Evidence of This Behavior in Africa

The tiny fish, called shellears, use microscopic hook-like growths on their fins to ascend—and they take a lot of breaks. The full climb probably takes about ten hours, according to a new study

Sara Hashemi | Daily Correspondent

April 9, 2026

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For more than 50 years, people have talked about tiny freshwater fish called shellears scaling the rock faces behind waterfalls in Central Africa. But the behavior has never been officially documented—until now.

These rock-climbing fish have moved beyond tall tales thanks to videos and photographs of their journey up the 50-foot Luvilombo Falls in the upper Congo Basin, along with a description of how they pull off the monumental feat. The findings, published April 2 in the journal Scientific Reports, have important implications for conservation in the region, as shellears’ migration makes them particularly vulnerable to habitat loss and illegal fishing.

“Who would have believed it without being close enough to check, and document it with photographic and film material, that indeed some fish are able to ​climb waterfalls?” says study co-author Pacifique Kiwele Mutambala, an ichthyologist at the University of Lubumbashi in the Democratic Republic of the Congo (DRC), to Reuters’ Marta Serafinko. “It illustrates that there are wonders out there that surpass our imagination.”

Supplementary video 3 (Kiwele et al. Scientific Reports)

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Researchers have witnessed rock-climbing fish in other parts of the world, including South America, Asia and Australia, but never in Africa. Seventeen years ago, however, study co-author Auguste Chocha Manda, also an ichthyologist at the University of Lubumbashi, filmed thousands of shellears belonging to the species Parakneria thysi ascending Luvilombo Falls in the DRC. But he lost the footage, reports NPR’s Ari Daniel.

So, the team went back and observed the species at the end of the rainy season in the spring of 2018 and 2020. The fish mostly scaled the waterfall during major floods, and their migration peaked in mid-April, the researchers found. The creatures use hook-like single-cell structures on their fins to grip onto the rocks. Then, they wiggle their tails to give themselves momentum.

“It’s as if the fish is swimming but in vertical,” Kiwele Mutambala tells Elizabeth Anne Brown at Scientific American. “It’s beyond imagination.”

The journey is difficult for the fish, and one with a lot of breaks. They’ll have a spurt of upward movement, followed by a rest that can last from 15 seconds to an hour or more. The team calculated that the full trip up the waterfall should take about ten hours.

Many fish also fall, forcing them to restart their trek. What’s more, while the animals can grow to be nearly four inches long, only those under two inches were seen climbing. The larger ones “become too heavy, and so the animal cannot bring its own weight to the top of the falls,” says Emmanuel Vreven, a study co-author and ichthyologist at the Royal Museum for Central Africa in Belgium, to NPR.

The scientists aren’t sure why the fish are such intrepid adventurers. They might climb to evade predators or competitors for food, or perhaps they’re looking for mates upstream. Regardless, it’s “fabulous” to see a fish use “friction enhancers” to stick to the rocks and climb, says Adam Summers, a biologist at the University of Washington who wasn’t involved in the work, to Scientific American.

Understanding the fish’s migration route is also important for understanding the region’s ecosystem. During the dry season, people sometimes turn off Luvilombo Falls’ water supply and reroute it for crop irrigation. The animals’ congregation at the bottom of waterfalls also puts them at risk of being caught in large, surrounding nets, a fishing practice that is forbidden in the DRC, the study authors write.

“This discovery highlights the importance of maintaining the continuity of watercourses, particularly in the ​context of the Congo Basin, where studies on fish behavior are virtually nonexistent,” Kiwele Mutambala tells Reuters.

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.