For nearly all fish, water is life. Yet, one species in the Democratic Republic of Congo (DRC) defies expectations by climbing waterfalls—a feat documented by biologists after decades of local reports. The shellear fish (Parakneria thysi ) spends up to 10 hours scaling cliff faces, pushing the boundaries of what we think fish can do.
The First Scientific Proof
Stories of these tiny, 1.4 to 1.9-inch fish have circulated for over 50 years in the DRC, but lacked concrete proof until now. Researchers led by biologist Pacifique Kiwele Mutambala from the Université de Lubumbashi observed the shellears firsthand at Luvilombo Falls between 2018 and 2020, capturing photographic and video evidence.
The fish’s climbing season occurs between April and May, after heavy rains. Using hook-like growths on their pectoral and pelvic fins, they pull themselves upward, aided by sideways body movements for extra momentum. The process is brutal: scaling a 50-foot cliff takes nearly 10 hours, broken into 15 minutes of climbing, 30 minutes of resting, and nine one-hour respites. Often, strong currents knock them back down, forcing them to restart.
Why Climb?
Biologists suggest two main reasons. First, floods may wash fish downstream, prompting them to climb back to their preferred habitats. Second, these climbs could lead them to less competitive feeding grounds and safer zones away from predators like the silver butter catfish.
However, this behavior is making the fish vulnerable to illegal fishing. Worse, plans to divert the river for irrigation pose an existential threat: without conservation support in Upemba National Park, the shellear population could vanish entirely.
This study isn’t just about an amazing fish; it’s a call to protect a fragile ecosystem that’s being squeezed by human activity.
The researchers hope documenting this remarkable behavior will draw attention to the DRC’s biodiversity and the urgent need for its preservation. The shellear’s struggle to climb is a metaphor for the larger battle to save this unique environment.
