Of all the species of ﬁsh in the world, one quarter of them shoal and/or school for their entire lives, while about one half participate in the action for limited periods. Together this means that vast selections of ﬁsh school at some point or another, coming together to swim in synchronicity.
Fish perform this phenomenon for a number of reasons. The ﬁrst is to support social and genetic functions, aggregating together to increase the ease of communication and reduce stress – experiments have shown that heart rate reduces signiﬁcantly in shoaled ﬁ sh compared to those alone. The second advantage of schooling is to boost the group’s foraging success, which has been proven in trials to grow considerably in comparison to a solitary specimen. This is simply because the number of eyes looking for food increases dramatically and, partnered with the ability for each ﬁsh to monitor the behaviour of those around it, means that when one ﬁ sh demonstrates feeding behaviour, the others follow.
Finally, the third – and primary – reason why ﬁsh school is for protection. By grouping into a tight, regimented pattern, the ﬁ sh minimise their chance of being picked off by generating a sensory overload to a predator’s visual channel. The swirling mass of twisting silvery ﬁsh creates a blending effect where the predator struggles to track a single target and becomes confused.