Fish in schools can take it easy

Using a new computer model, researchers at the Ecole Centrale de Marseille and CNRS have shown that a fish expends less energy when it swims in a school, because neighbouring fish produce a 'suction' effect. This work will be published on 11 May 2018 in Physical Review Letters . Schools of fish provide a fascinating example of collective behaviour in which the group moves in a coordinated manner without the need for a leader. In the past, many computer models have shown that such collective motion can emerge from simple rules: each individual tends to align itself with its neighbours and move towards them while avoiding collisions. However until now, no research into the role of water flow between fish had ever been carried out. To investigate this question, a group of fluid mechanics specialists at the Institut de Recherche sur les Phénomènes Hors Équilibre (CNRS/Aix-Marseille Université/Centrale Marseille) and physicists at the Laboratoire de Physique Théorique (CNRS/Université Toulouse III-Paul Sabatier)¹ developed an original model that incorporated flow dynamics within a school numbering hundreds of fish. The path of each individual is governed by classic rules of attraction and alignment, as well as translation and rotation effects caused by the flow generated by the other fish.