Manica and his colleagues monitored individual threespine sticklebacks (Gasterosteus aculeatus) for their willingness to leave their safe, weedy cover and venture out into the risky, open waters to feed -- an indication of fish temperament.

A matter of fish personality
They then randomly paired fish of varying bravado, and discovered that the daring fish tended to lead and the shy fish opted to follow. Such personality traits were not too long ago thought were uniquely human.

Manica's team also found that both leader and follow fish, when paired, responded to each other's movements, which led to stronger leaders, more faithful followers, and, ultimately, greater foraging efficiency -- a phenomenon driven by what the authors call "social feedback". The behaviour you get from the pair is totally different from what you see in individuals, which is the result of this feedback

Another study by Jens Krause of the University of Leeds on larger groups of fish corroborate Manica's findings. Krause created quartets of guppies (Poecilia reticulate) consisting of all bold individuals, all shy individuals, or two of each temperament, and showed that the mixed personality shoal had the greatest foraging success. Together, these studies provide a potential mechanism for maintaining individual-level variation in behavioural traits related to personality

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