Steering mechanism of fish schools

The steering mechanism of fish schools was analysed by using an analytical model and computer simulation. The analytical model is based on fundamental behavioural rules such as attraction, parallel-orientation, and repulsion. Multiple individuals following the same rules interact with each other and thus realize school movements. The results show that when the school advances, unstable movements by the front individuals cause a change in the moving direction of the individuals that follow that individual. The transmission of the change in moving direction of the front individuals to rear individuals depends on how the individuals react to the motion of their neighbours. When the individuals react mainly to the motion of their front neighbours, the change in direction of the front individuals is transmitted quickly to the rear individuals, resulting in sharp turns by the school. In contrast, when the individuals react mainly to the motion of their side neighbours, the change in direction of the front individuals is slowly, if at all, transmitted to the rear individuals, resulting in only gradual turns by the school. Our results show that the transmission of information among individuals affects the macroscopic behaviour of the school.