Trajectories of schools of Hemigrammus rhodostomus under various confinement densities conditions

Confinement-driven state transition and bistability in schooling fishAbstractThis study explores the collective behavior of schooling fish, under controlled experimental conditions. We demonstrate a continuous state transition in the school behavioural state controlled by confinement density, i.e the number of individuals in a group per unit area of available space. The school exhibits a bistable state, alternating between a polarized state (aligned motion) and a milling state (vortex-like rotation). The transition dynamics are captured by a two-state Markov process, revealing that confinement density influences the stability of each state and the statistics of state transition times. These findings emphasize the crucial role of confinement in shaping collective behavior in moving animal groups, providing valuable insights for active matter models of confined agents and contributing to our understanding of how environmental factors influence complex biological systems.Data repositoryThis repository contains :The raw experimental data (15 min recordings of schooling fish) with name of the form YYYYMMDD_nnA table "exp_table.csv" to link an ID (of the form MMDD_nn) to a given set of experimental parameters (namely a pair of Available swimming surface area S, Number of fish in the school N.)The tracking files with names of the form YYYYMMDD_nn_tracking.csv