The adaptive significance of schooling as an anti-predator defence in fish

Fish in schools benefit from increased vigilance and, as a consequence of inspection behaviour, predator recognition and assessment is improved. Schooling behaviour and inspection behaviour may inhibit attack by predators, and, if schools are attacked a variety of tactics, ranging from the confusion effect to the flash expansion, serve to protect individual members. There are however a number of constraints on the evolution of schooling and associated anti-predator mechanisms. Conflicting selection pressures, such as the need to forage, mate and avoid predation, can operate simultaneously. Selection pressures acting on immature and adult fish may be discontinuous necessitating a period of increased vulnerability when individuals switch tactics. Schooling may not be an equally appropriate defence against all predators and the phylogenetic origins of populations or species can lead to additional genetic constraints. -from Author