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SYGF: Guest Country Symposium France: Soft, Active and Alive: Emergent Properties in Living Matter

SYGF 1: Guest Country Symposium France: Soft, Active and Alive: Emergent Properties in Living Matter (SYGF)

SYGF 1.6: Hauptvortrag

Mittwoch, 11. März 2026, 17:45–18:15, HSZ/AUDI

Perturbing the collective motion of fish with challenging environments — •Aurélie Dupont — LIPhy, CNRS Univ. Grenoble Alpes, Grenoble France

Collective movements can be observed across species and on various scales: from bacteria to mammals. We are interested in the collective behavior of small fish when confronted with external physical perturbations. When forced to escape through a narrow opening, most animals behave like granular materials and clogging events decrease the efficiency of evacuation. In this emergency exit scenario, we challenged the gregarious behavior of a group of macroscopic aquatic agents, neon fish, by forcing the school to pass through a small opening[Larrieu, Sci. Rep. 2023]. Using a statistical analysis developed for granular material and applied to crowd evacuation, our results clearly show that, unlike human crowds or herds of sheep, no clogging forms at the bottleneck. The fish do not collide and wait by respecting their social distance and a minimum delay between two successive exits. In a second experiment, we perturbed the schooling behavior of a group of zebrafish by adding an array of pillars to the observation tank[Ventejou Phys. Rev. E 2024]. We observed a behavioral transition from a polarized group when the density of pillars is low to independent fish aligned with the array of pillars. The abrupt transition from natural to artificial orientation occurs when the distance between pillars is comparable to the social distance of the fish. We developed a stochastic model of relative orientation between pairs of fish that captures the behavioral transition and provides information on the evolution of cognitive parameters.

Keywords: collective movement; living matter; collective behavior; fish school