Swimming in a school has a lot of benefits for fish, from social opportunities to avoiding predators to finding more food. One advantage, though, might be unexpected: a school of fish is quieter than a single one.
Engineers created a 3D model of mackerel in order to study the fish in a variety of common maneuvers, formations, and levels of synchronization and found that fish that coordinated their movements were able to significantly reduce their sound. In fact, 7 fish together only emitted the sound of a single fish! The secret to the quietness of the fish isn’t uniformity, but complementarity, specifically in how they move their tails. To swim, fish flap their tail fins. If a school of fish were to do so in unison, they would generate a lot of noise. But, if the fish alternate the movements of their tails, their movements create opposing sound waves and reduce the overall noise dramatically. The reason for this is a basic principle of oscillation in sound waves. Two waves oscillating in unison can add up and double the strength of the noise, but two waves oscillating at the same frequency but in inverse directions will cancel one another.
Reducing the amount of sound means that sharks and other predators might hear a group of fish and be less tempted to gobble them up because the group only sounds like an individual. The alternating movements have the added bonus of reducing the amount of energy fish need to swim, thus allowing them to swim faster as a group. Schools, for fish as for people, have numerous and sometimes unexpected benefits.
