Scientists at LIPhy have highlighted the existence of a behavioral transition when the environment of zebrafish becomes too cluttered, showing how far the collective school structure can withstand the structural complexity of the surrounding environment.
Group of zebrafish swimming in a network of obstacles with varying density. Analysis of relative orientations between fish in very low and very high obstacle density cases
© benfilm.
The study of collective movements helps better understand the dynamic structures resulting from the self-organization of groups of individuals. The schooling of fish is remarkable because it forms in various environments such as the open sea or amidst corals. Research in this field has focused so far on studying schools in simple environments, devoid of obstacles.
In recent work, a team from the Laboratoire Interdisciplinaire de Physique (
LiPhy, CNRS / Université Grenoble Alpes) used an approach combining experiments and modeling to study the impact of a complex environment on the collective organization of a fish school. For this, the individual trajectories of a small group of zebrafish were recorded in the presence of obstacles, the number and density of which were varied.
The structure of the fish school proved to be quite resilient to the introduction of obstacles, maintaining an organization similar to that observed in open water. However, when the distance between obstacles becomes small enough, the school structure gradually disappears, and the fish behave as if isolated, aligning with the physical environment rather than with their peers. The obstacle density at which this transition occurs corresponds to a distance between obstacles close to the typical distance between fish in an undisturbed school, i.e., their natural social distance.
Thanks to a statistical model, the ingredients of this behavioral transition, from collective to independent, were analyzed in detail. The physicists demonstrated that a structured environment can significantly influence fish behavior and that social distance is critical to maintaining collective behavior in a complex environment. These results contribute to the emerging field of active and cognitive matter, and more broadly to the study of animal behavior or swarm robotics by biomimicry. They are published in the journal
Physical Review E.
Reference:
Behavioral transition of a fish school in a crowded environment,
Bruno Ventéjou, Iris Magniez-Papillon, Eric Bertin, Philippe Peyla, and Aurélie Dupont,
Physical Review E, published on June 11, 2024.
Doi:
10.1103/PhysRevE.109.064403
Open archive:
arXiv