These Tiny Fish Can Climb 50-Foot Waterfalls—and Scientists Finally Have Proof of Their Skills
The freshwater species, called Parakneria thysi, is roughly comparable in size to a thick french fry.
For decades, people in Central Africa told stories about the tiny fish that could somehow scale tall waterfalls. Most scientists couldn’t confirm the claims, and the accounts remained largely unproven. But now, thanks to fieldwork conducted between 2018 and 2020, researchers have the evidence to back up what once sounded like pure myth—and the story behind it is nothing short of extraordinary.
These remarkable little climbers aren’t powerful, muscular fish. They are quite tiny, but their abilities are so impressive.
Parakneria thysi Fish are barely the size of a french fry
The freshwater species, called Parakneria thysi, is roughly comparable in size to a thick french fry. Yet researchers studying the Luvilombo Falls in the Democratic Republic of the Congo used photos and video to document thousands of these tiny fish scaling vertical rock faces during seasonal floods. The waterfalls they climb reach up to approximately 15 meters—about 50 feet—high, and they often make the journey in groups numbering in the thousands.
To put that in perspective, researchers have likened the climb to a salmon scaling something as extreme as Niagara Falls or even the CN Tower. The behavior suggests a large-scale migratory strategy rather than an isolated oddity.
“If you would ask a regular person, do you think fish can climb falls, most of them will tell you: you are crazy,” says Emmanuel Vreven, an ichthyologist at the Royal Museum for Central Africa in Belgium, per NPR. “Well, it exists, it is out there.”
How Emmanuel Vreven and researchers discovered the fish climb
So how does a fish the size of a fat french fry defy gravity? Vreven and his fellow researchers found the answer lies in specialized anatomical adaptations. The fish have hook-like projections on their pectoral and pelvic fins that function like Velcro, enabling them to grip slippery rock surfaces under strong water current. Their locomotion combines fin-based adhesion with body undulation, allowing individuals to inch upward against gravity and flowing water.
“You see also the lateral undulations of the fish very fast. It’s as if they are swimming vertically,” Vreven says. The movement is called a power burst. Researchers reinforced these findings through detailed methods such as frame-by-frame video analysis and CT scanning, confirming both the mechanics of movement and the structural adaptations involved.
The Parakneria Thysi climbing journey takes up to 10 hours
Despite the dramatic visuals, the ascent is surprisingly slow. While the total journey can take 9 to 10 hours, the fish spend only about 15 minutes actively moving. The rest of the time is devoted to extended rest periods that help them conserve energy.
“When they arrive at a flat surface,” Vreven says, “they will pause for a longer time. When they recover the energy, they can begin another step of the climbing. Most of the time is in fact resting.”
The climb is also risky. Individuals can be dislodged by fast-moving water or struggle to navigate complex features such as overhangs. Climbing success is size-dependent, with only smaller individuals, generally under 48 mm, able to complete the ascent.
Why these tiny fish risk the dangerous climb
This behavior is closely tied to seasonal flooding, which can wash fish downstream. By climbing waterfalls, the fish may avoid predators, reduce competition and access more favorable conditions. The path to this discovery stretches back roughly 17 years, when long-standing rumors first drew scientific curiosity. It took patient fieldwork in a remote region of the Congo to finally turn local knowledge into a landmark scientific finding.
The study also underscores broader conservation concerns. Migratory species like Parakneria thysi are particularly vulnerable to extinction, especially in the face of human activities such as overfishing and river modification.
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