Mesoscopic wave physics in fish shoals

TL;DR

This paper demonstrates that dense fish shoals exhibit mesoscopic wave interference effects similar to those in disordered electronic or optical systems, revealing slow energy transport and proximity to localization.

Contribution

It provides the first large-scale experimental evidence of mesoscopic wave phenomena in biological systems, linking fish structure to strong scattering and wave localization effects.

Findings

Ultrasound scattering shows mesoscopic interference in fish shoals.

Strong deviations from classical diffusion are observed.

Fish shoals are near the Anderson localization transition.

Abstract

Ultrasound scattered by a dense shoal of fish undergoes mesoscopic interference, as is typical of low-temperature electrical transport in metals or light scattering in colloidal suspensions. Through large-scale measurements in open sea, we show a set of striking deviations from classical wave diffusion making fish shoals good candidates to study mesoscopic wave phenomena. The very good agreement with theories enlightens the role of fish structure on such a strong scattering regime that features slow energy transport and brings acoustic waves close to the Anderson localization transition.