Illuminating synchronization behaviors in schooling fish

Animals often form groups to maximize their efficiency. Many migratory birds, for instance, fly in formations designed to conserve their energy over long flights. Some species of fish do the same, although the mechanisms governing those behaviors are less well understood. Ito and Uchida developed a theoretical model to explore how fish can adapt their motion to exploit wake vortices generated by a nearby companion to reduce their energy consumption.

Experimental studies of schooling fish have shown they synchronize the beats of their tails when swimming together.

“Previous models of fish swimming in a pair or a group prescribed the fin motion as a function of time, and therefore did not reproduce their spontaneous coordination of tailbeat,” said author Susumu Ito. “By incorporating physiological noises, we reproduced the autonomous time-evolution of tailbeat, which enabled us to study the coordinated motion in a statistical manner that is comparable to the previous experimental results.”

The duo’s approach allowed them to model the gradual synchronization of tailbeats and observe the resulting reduction in energy dissipation rate. They found the most probable coordination pattern is not the one that minimizes energy dissipation, a result that questions the conventional working hypothesis.

“We plan to extend the study to a group of fish by incorporating a dipolar flow pattern that is expected to be more effective than the vortex flow at far distances,” said Ito. “Also, we plan to consider other types of interactions between fish, such as those through visual information and other types of responses such as escaping from predators.”

Source: “Vortex phase matching of a self-propelled model of fish with autonomous fin motion,” by Susumu Ito and Nariya Uchida, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0173672 .