Dominating Lengthscales of Zebrafish Collective Behaviour

TL;DR

This study investigates the collective behavior of zebrafish, identifying key length scales that characterize behavioral states and linking these to collective motion through a simplified particle model.

Contribution

It introduces a three-dimensional analysis of zebrafish behavior and links length scale ratios to collective motion, advancing understanding of fish shoaling dynamics.

Findings

Two key length scales identified: persistence length and nearest neighbor distance.

Ratio of these length scales correlates with the degree of collective polarization.

A reductionist model explains the observed behavioral transitions.

Abstract

Collective behaviour in living systems is observed across many scales, from bacteria to insects, to fish shoals. Zebrafish have emerged as a model system amenable to laboratory study. Here we report a three-dimensional study of the collective dynamics of fifty zebrafish. We observed the emergence of collective behaviour changing between \yy{ordered} to randomised, upon \yy{adaptation} to new environmental conditions. We quantify the spatial and temporal correlation functions of the fish and identify two length scales, the persistence length and the nearest neighbour distance, that capture the essence of the behavioural changes. The ratio of the two length scales correlates robustly with the polarisation of collective motion that we explain with a reductionist model of self--propelled particles with alignment interactions.