The fish is a Chaetostoma microps, commonly known as the armored catfish. Researchers filmed the creature scooting up the wall in a cave located near Tena, Ecuador.
"We may be watching a small but significant evolutionary step as a species moves from one niche to another," expedition leader Geoff Hoese told the BBC.
'It's not too surprising to find another catfish that climbs rocks," he continued. "What is surprising is the environment that they are doing it in."
https://youtu.be/YyzPZfCbC-s
Researchers believe the catfish is climbing in order to eat algae on the roof of the cave. Scientists are puzzled by more than the fish's climbing. They also want to know more about how the animals got into the cave system.
A study in Subterranean Biology confirmed it's the first time the behavior has been filmed.