How do schools of fish swim in perfect unison?

Fish follow a few simple rules to form complicated choreography in groups.

21st November 2017
How do schools of fish swim in perfect unison? © Getty

Asked by: Leslie Dawes, Petersfield

A fish decides where and how to move relative to its position in the school. If the fish behind gets too close (less than two body-lengths), then it speeds up; if the fish in front gets closer than that, then it slows down. Schooling fish watch one another and also feel the waves their neighbours make as they swim, with pressure-sensitive pores along their body called the lateral line. And each fish has its preferred spot in the school. Some are natural leaders and tend to hang at the front and guide the whole school, while others choose to follow.

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