Why Do Fish Swim in Schools?

Fish swimming together is a great example of "safety in numbers". In a school, the fish in the middle of the group are well protected from predators and the abundance of the fish in one area may confuse actually confuse the predator making them less efficient on hunting.

There is one downside to being in the middle of the pack - lack of oxygen. Scientists have found that fish swimming in the middle of a school have access to 25% less oxygen than the fish swimming on the periphery. This causes the school to change shape frequently as fish move from the inside to the outside of the formation.