How flashlight fish communicate with light signals in the school

Flashlight fish have the ability to generate situation-specific blink patterns resembling a visual Morse code. Researchers have shown in laboratory and field experiments that the animals use these light signals to coordinate their behavior in the school when visibility is limited. Both the light intensity and the blinking frequency affected the animals' behavior.

source https://www.sciencedaily.com/releases/2021/03/210319125439.htm