Why do fish swim in schools

School of fish

Photo: editorial staff

Not only during adolescence, when you have to protect yourself from predators, fish form so-called schools, but also when they are fully grown fish are grouped in schools. Norwegian researchers at the Institute for Marine Research (IMR) are studying how decisions are made in schools of fish.

Basically, the question arises why swarms are formed. One of the main reasons is protection from predators. It is interesting that the predators in turn form fish schools at a young age. If barracudas and hammerhead sharks are considered loners in old age, these fish species can be observed in schools at a young age. Other reasons for the formation of schools are overwintering and the breeding behavior of the fish.

If a school of fish is attacked, the fish begin to swim in circles. The Norwegian researchers want to find out how decisions are made in a swarm. Are the predators the triggers that force the fish to swim in circles, or is this behavior generated by the school? Killer whales have developed a unique hunting strategy in which they round up the swarm and force it to rise to the surface of the water.

A school of fish is seen as a leaderless, self-organizing system. The movements and decisions of the individual fish are mainly made by imitating the reactions of the neighboring fish. The millions of individual decisions are made from the inner motivation and the need to survive of every single fish. Seen from the outside, this behavior appears to be a collective decision.

It is not a democratic process that underlies collective behavior. Rather, the behavior can be compared with physical laws. The swarm moves in the direction of least resistance. That means he moves away from the attacker. The formation of a circle or a sphere also gives the swarm the smallest surface area for an attack. The Norwegian researchers compare this behavior with the historical, collective decision of people to speak the same language.


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