shoal

Ichthyologists have recently determined that social fish “smell” distinctly different to members of their own species according to maturity and size. Researchers believe that this mechanism developed in order that schools of fish could more quickly gather and sort themselves for protection, assuming a uniform front against predators, since from a fish-perspective, I imagine that it would be hard to judge size by sight. Schooling also helps with foraging for food and facilitates finding a suitable fish-mate.