Collective effects in complex environments in fish

Context :

In situ studies have identified the benefit of such schooling behaviour: energy saving for swimming, visual effect for fighting a predator. Recently, experimental studies in the laboratory have also made it possible to test interaction models between individuals in a simple environment. Some phases of collective movements have been characterised by different dynamic models of non-equilibrium systems. We have recently proposed a model, purely orientational, which shows the gain in rheotaxis performance (alignment with respect to a flow) in the presence of collective interactions[1]. However, no model yet fully couples social forces and hydrodynamic interactions.

Objective :

The objective of our work, both experimental and numerical, is to go beyond the observation of groups of free-swimming fish and to disrupt this self-organisation by a complex environment (pillars, constriction, flow). Interfering with the interactions between fish allows us to probe a little bit more into the mechanisms of these interactions. The objective of the internship will be to study the behaviour of groups of fish in the presence of obstacles imposing a minimal inter-fish distance and hindering visual and hydrodynamic interactions. Preliminary work has already been carried out in the absence of flow[2,3]. During the internship, the experiment will be replicated in the presence of a controlled flow, which will allow the models under development to be tested.

Team :

This internship topic is part of a larger interdisciplinary project. We are working in collaboration with P. Peyla (LIPhy) for the modeling, T. Métivet (INRIA) for the numerical integration of the hydrodynamics and C. Graff (LPNC) for ethology. On a daily basis, the trainee will be able to interact with a PhD student working on a similar topic, and periodic meetings with all partners will be organised.

Keywords : physics of biological systems, active matter, collective effects, image analysis (Python)

References :

[1] Larrieu et al. Collective orientation of an immobile fish school and effect on rheotaxis. Phys. Rev. E 2021
[2] Larrieu et al. Forcing a fish school to a bottleneck: a smooth evacuation. ArXiv:2212.12514. 
[3] Magnier-Papillon et al, Collective behavior of a fish school in a crowded environment. (In preparation)