Why Do Fish Swim in Schools?
Fish form schools for protection from predators, schools containing hundreds or thousands of nearly identical fish can confuse predators and make it difficult to single out and attack an individual.
Small fish in a dense school, moving in unison, may discourage a predator by appearing as a single, much larger creature.
Schooling makes it easier for fish to find food. With many more eyes on the lookout, more meals are possible. By working as a team, a school may be able to seize larger food items than any one fish could manage to capture.
Another benefit of schooling is that it brings the sexes together and increases the odds of successful reproduction. Many fish species form schools only when it is time to mate.
Schooling also increases the efficiency of swimming for fish. Drafting in the wake of their schoolmates allows fish to conserve energy, swim longer and even consume less oxygen than they would if swimming alone.
Generally comprised of fish of the same age and size, schools typically face in one direction and exhibit synchronized movements. Each fish maintains an exact spacing from its neighbor. As they swim, they follow the movements of their neighbors and change their course in unison.
Not all fish shoal or school, though. Scientists estimate that at least 80 percent of all fish will school at some time in their lives. Some fish — often larger species — choose to live solitary lives.