In a stunning example of group defense, a huge mass of juvenile striped eel catfish move as one to fend off predators. A video taken by Marie-Laure Vergne, an instructor at the Abyss Dive Center Bali, shows these youngsters as they move across the ocean floor. Undulating in a mass, their movements are mesmerizing.
As adults, the striped eel catfish is highly venomous and can inflict real pain. But while they're still growing, the full power of their venom hasn't set in. “The young ones can only produce a mild version of the venom, tingling the fingers of the people putting their hands in the school (which we don’t recommend you do!),” writes the Abyss Dive Center Bali.
With this information in hand, it makes sense that they're ganging up and make sure the entire group is safe rather than taking on predators alone. Together, the move as one and make for a formidable opponent. If you look closely at the video, you'll notice that the individual fish aren't static. Instead, they each move up and down as the mass moves forward—almost like a waterfall of catfish. As each fish hits the sand, their barbed faces look like little feet scurrying along.
Schools of young striped eel catfish can reach up to 100 individuals. As they get older, they'll then move into a more solitary lifestyle. These fish typically stay to themselves or, at most, live in a group of up to 20. They spend their days hiding under ledges and stirring up sand to find crustaceans, mollusks, and worms. But until then, they can enjoy this time together with their peers, flowing through the water and warding off anyone who dares get in their way.