https://phys.org/news/2018-11-responses-coral-reef-fish-simple.html

"We took an approach used in laboratory studies into a complex, natural environment and found that the same behavioral mechanisms seem to apply. A set of simple rules are combined in different ways to generate a rich suite of behaviors to accomplish this fundamental goal: to avoid being killed," said first author Andrew Hein, an assistant researcher at the UC Santa Cruz Institute of Marine Sciences and research ecologist at the NOAA Fisheries Lab in Santa Cruz.

The coral reef fish in the study feed on algae in shallow reef flats, where they are vulnerable to predators such as moray eels and reef sharks. To simulate a threat, the researchers employed a widely used visual stimulus called the looming stimulus, a black dot that grows in size slowly and then rapidly, creating the illusion of a rapidly approaching object. A waterproof tablet computer deployed on a coral reef in Mo'orea, French Polynesia, played the looming stimulus, while video cameras recorded the responses of fish that swam into the area in front of the tablet.