This image is a visualization of 150 fish (Notemigonus crysoleucas) free-swimming in a shallow 2.1 x 1.2 meter tank. It shows the recorded position of the body and eyes of each fish in the school for one frame of video.
Superimposed is a two-dimensional approximation of the field-of-view for each eye of each fish, shown as white rays cast outwards from the eye. Rays are terminated when they collide with another individual or the boundary of the arena.
This rough estimate of what each fish can see from its vantage point in the school is helpful for determining what information an individual has about its neighbors and environment at a given moment. This in turn allows us to study how information about a stimulus (for example, a predator or food in the environment) may propagate through a group -- changing the configuration of the group itself.