Why do some fish travel in huge schools?

Fish school for several reasons, and the benefits are strongest in open water where predators are common. A large group can confuse attackers through the “confusion effect,” making it harder to isolate one fish. Schooling also helps fish save energy by using hydrodynamic benefits from swimming close together, and it can improve foraging and migration. Sardines, anchovies, and herring are classic schooling fish, often forming massive coordinated groups. The behavior is driven by visual cues, lateral-line sensing, and simple rules that let the group move with remarkable coordination.