The waterfall-climbing fish that defies gravity by climbing vertically up a 50-foot waterfall.
The fish is known as the shellear (Parakneria thysi) found in the upper Congo Basin. For decades, locals described this little fish actually climbing straight up waterfalls, but scientists had no proof—until field research captured video & photographic evidence between 2018-2020. Researchers documented the fish scaling a 50-foot vertical rock wall, with thousands migrating upwards during the rainy season. Even human climbers would be hard pressed to be able to accomplish this. The way they accomplish this is with hooks on their fins that act like Velcro, gripping wet rock. The fish presses its body flat against the cliff, reducing drag while increasing friction. They move upward by swinging its tail side-to-side, essentially "swimming" vertically and advancing a few millimeters at a time.
The climb takes 9 hours & 45 minutes, yet it swims for only 15 minutes of that time. Many fall off & have to start all over. The reason the climb takes so long is that there are 9 major ledges where they rest for an hour each time. They also take 30 minutes of micro-pauses lasting 15 seconds to a minute. These brief pit stops gives the animal just enough time to recover its strength for the next push. They climb in the splash zone, not the main jet force of the fall, just enough to stay wet but not enough to blast it off. This is the same physics that lets a gecko cling to a vertical wall—but wetter, slipperier, & with more death involved, perhaps in the range of 30-70% mortality. This is because the fish is only 2 inches big, & a sheer drop into turbulent waters, rocks, & predators means most falls are not survivable.
Why does it take the risk & climb at all? It is to reach new spawning sites and better upstream feeding grounds. Heavy rains might wash the fish downstream, forcing them to climb back up to their preferred habitats. It also helps them escape crowded feeding grounds or evade predators lurking at the waterfall's base. One such threat is the silver butter catfish, a hungry predator that congregates downstream. If they don't climb, they can't complete their life cycle. This is a partial migration—not all individuals do it, but thousands do.
Incredibly, it has no suction cups, no adhesive mucus, no muscular inchworming ability, and no limb-like fins, but it does have a streamlined body, a powerful tail & microhooks for grip. Biologists call the hooks uncull. This is the first African waterfall-climbing fish. A few other fish also climb, but with different mechanisms. The Hawaiian gobles use suction-cup pelvic fins & their mouths, South American catfish & lumpsuckers use suction cups formed from their mouths or modified fins to grip wet stones. The natural world is full of overlooked wonders, not least the tiny shellears of the Congo.
