Scientists know that little fish form tight-knit schools to avoid being eaten. But as new research shows, schooling fish get another advantage—more efficient swimming, and more energy for a hasty retreat from predators.
Schooling fish often swim in a staggered diamond pattern, riding the wake of whoever’s in front. In principle, thanks to the physics of fluid dynamics, this should save the fish some effort. A beating fish tail creates a small vortex in the water behind it. If a fish swims directly behind its leader, these vortices push against it, forcing the follower to swim harder.
But that theory, first outlined in a 1973 paper, has been largely untested until Benjamin Thiria, a biomechanics researcher at ESPCI Paris in France, and his co-workers took up the challenge. They found that not only do fish indeed save energy when they swim in a diamond formation, but also that when fish swim very quickly—such as when they need to evade predators—they fall into a different energy-saving formation: synchronized rows.
Photo: Bruno de Giusti/Wikimedia Commons (CC BY-SA 2.5)