Benefits of Schooling

Two robotic fish swimming side-by-side with wakes made visible through dye.

Though fluid dynamicists have long theorized about the hydrodynamic benefits of fish swimming in schools, nailing down the actual physics has been quite difficult. Fish rarely swim exactly as an experimenter would like, and measuring quantities like swimming efficiency in a living fish is tough to do. In the numerical realm, it’s tough to simulate multiple fish swimming at realistic conditions. So some teams have turned to biomimetic robotic platforms to study schooling, as in this new research.

Once you’ve built a robotic fish that swims in a realistic way, that fish will have no problem swimming the same experimental patterns over and over. In this work, the researchers compared their robots swimming solo and swimming with a partner. In the partnered studies, they looked at fish swimming in phase — with their undulations matching one another — and out of phase — where the fish move opposite one another. They found that having a nearby partner improved the speed and efficiency for both fish, regardless of phase. But they also found a peculiar exception.

If one fish modifies their tailbeat frequency relative to their partner, they can slightly increase their power efficiency. But if they do so, it costs their partner more energy. That implies that fish could employ competitive dynamics, but, of course, it doesn’t tell us that they do! (Image and research credit: L. Li et al.; submitted by Kam-Yung Soh)

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