Finding Fish Couzin dives into the sea. Just below the sea’s surface, something flashes. It’s a big school of fish. T ese fish ride the ocean currents side by side. As they change direction, their silvery sides reflect flashes of sunlight. Together, these fish look more like one large


fish than hundreds of small ones. T is swarm behavior helps confuse many predators. Yet when it comes to a school of sardines, sailfish aren’t fooled. T ey dart out of the ocean depths. T ese fish raise their sails, a sign they’re about to attack. Each sailfish has a long sharp bill that looks like a sword. T e sailfish race toward the sardines. T e sardines bunch tighter together, swimming faster and faster. Like the starlings, each sardine watches the


ones closest to it to figure out where to swim. But that’s not the only sensory input these fish use to stay together.


A Feel for Danger Sensitive cells and hairs grow along a sardine’s sides. T ey let the fish feel tiny changes in the water. T ey can feel ripples from an attacking predator and water moving as the closest fish changes direction. T ese


stimuli tell the fish which way to swim. T e sailfish don’t give up, though. Pass


aſt er pass, their bills slice through the school. T e sailfish divide the school into smaller and smaller groups. Each group swims in a mini swarm. Yet staying together is not enough to protect all of them. A sailfish swats a sardine with its sharp bill


and knocks it out of the school. T e sardine can’t see any nearby fish now. It can’t feel which way to go. Without its swarm, the sardine is doomed. T e sailfish quickly gobbles it up.


OCTOBER 2014 7


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