When it comes to fish dynamics, there's a school

28 Mar 2024 Michael Banks

Researchers find that three fish is the minimum number to form a school. (Courtesy: University of Bristol/Yushi Yang))

How many fish make up a school? It sounds like one of those trick questions, but physicists at Heinrich Heine University Düsseldorf and the University of Bristol have now found an answer.

To do so they fitted a “bowl-shaped” aquarium at Bristol University with cameras to track the three-dimensional trajectories of zebrafish, studying group sizes of two, three, four and fifty fish (Nature Comms 15 2591).

The researchers then used methods from statistical physics to analyse swimming patterns and deduce the minimum group size where individual movements change and become coordinated group patterns.

They found that an isolated pair of fish prefer to move one after the other but when in threes the zebrafish swim next to each other – a characteristic of a large school of fish.

When the researchers then marked small sub-groups of three fish within a larger school, they found that the group of three moved within the school in a similar way to an isolated group of three. So, while three fish form a school, two are not enough.

The team now aim to apply their findings to the behaviour of other animals and how groups of people behave at parties or mass gatherings.

“We will see whether the simple limit of the number three also applies,” says Düsseldorf physicist Hartmut Löwen.

Michael Banks is news editor of Physics World magazine.

FROM PHYSICSWORLD.COM     30/3/2024