Nearly all fish spend their entire lives in water, but there are some that behave in ways that don’t fit the mold. The tiny shellear fish (Parakneria thysi) will spend hours crawling up the cliffs of Luvilombo Falls in the Congo Basin of Central Africa. It’s a remarkable feat of endurance, and if a stray jet knocks them off, they have to start all over again. “That would be like a salmon trying to make it over Niagara Falls,” said Steven Cook, a fish ecologist at Carleton University in Ottawa. Not all the fish make the climb — only the ones that are a couple of inches long or less. Any bigger and they are too heavy to bring their own weight to the top of the falls. In addition, the fish that do scale the cliffs do so in the center where the water flow is the strongest. One of the big questions is how they manage to climb. A group of researchers reviewed the fish’s vertical movements in video footage and ran CT scams to examine their anatomy. The fish actually support themselves with their rear pelvic fins, and their front pectoral fins have an array of tiny hooks that function like Velcro, which they use to grip the rock. They also have a heft arch of bone called the pectoral girdle that supports the muscles needed to make the climb. The scientists think that the shellears scale the falls as part of a migration upstream.
