School is important because it helps you meet new friends, teaches you about things like science and geography, keeps you from getting eaten by sharks, and... wait, what? Sharks?!
Sharks and other predatory fish probably aren't the biggest safety concern on your school yard, but for small fish in the ocean, keeping yourself from getting eaten is a full time job! For many fish, schooling behaviours are the best way to stay safe in a big ocean. When fish school together, they swim in large numbers using coordinated movements in the same directions. This video of a school of fish is pretty hypnotic to watch, and it has the same effect on potential predators—big hungry fish are unable to pick out any one fish to hunt, and watching the swirling motions of the whole school together can get pretty confusing for them. Also, when all these fish travel together, there are many pairs of eyes looking out for any threats. This makes it very difficult for any predators to pull off sneak attacks!
As effective as this is at discouraging hunting, some predators have figured out ways of disrupting schools to pick out single fish. Swordfish will slash through the cloud with their bills, sailfish will herd smaller groups away with their sails, and some species of whale will simply open their mouths wide, and swallow whole parts of the school at once! Schooling behaviours don't offer fail-proof protection, but by swimming together in large groups, small fish can greatly increase their odds of surviving over solo travel!
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