Mackerel forming a bait ball to avoid predators © Jordi Chias/Minden Pictures
This school of Atlantic horse mackerel is forming a bait ball. When surrounded by predators, such as the barracuda and bluefish seen here, the school will gather close together to expose the least number of individual fish. In the open ocean, without hiding places among kelp, coral, or coastal rocks, the bait ball will protect most of the smaller fish. Is this where the idea of ‘safety in numbers’ originates?