First-nearest neighbour interactions and Vicsek-type noise in shoals of Paracheirodon axelrodi fish.

While living individuals frequently behave independently of one another, they can coordinate to form dynamic ordered groups. The functional forms of these interactions in experimental systems are often unclear and/or complex. Despite the inherent complexity in experimental systems, the simplified interactions between active objects within the Vicsek model are sufficient to qualitatively reproduce some collective behaviours. This article aims to understand the simplified interactions between fish within experimental shoals by interpreting our experimental data, captured through video imaging, as Vicsek-type interactions. We find that Vicsek-type noise is controllable based on confinement, and a comparison with both metric and topological Vicsek models suggests that first-nearest-neighbour interactions best predict future fish orientations. These results promote our understanding of the interactions between fish.