Suspicious Fishes

But mom! EVERYONE’S doing it!

This is Sandra Tsing Loh with the Loh Down on Science.

A sudden flash of color, and a hundred fish change direction in unison! This fish ballet confuses predators, helping fish escape. But when fleeing danger, is it all for one, or a free-for-all?

Lauren Nadler at Nova Southeastern University in Florida and her team fished for answers. 

They studied damselfish, shiny blue-green ocean fish that swim in schools. They put groups of eight into separate tanks. Each group was either all friends from the same school, or strangers. 

Then, the researchers simulated a predator attack by dropping objects into the tanks. They filmed the damselfish-in-distress with a high-speed camera to measure their reaction times. 

How did our little swimmers fare?

Friendly groups were more on the ball than strangers. Groups of strangers took almost FIVE TIMES as long to dart away! The team thinks that damselfish build trust over time with each other. If a schoolmate suddenly bolts, trust their instincts – and copy them FAST! 

Looks like these fish can SCHOOL us on friendship!

Reference: Nadler, L.E., McCormick, M.I., Johansen, J.L. et al. Social familiarity improves fast-start escape performance in schooling fish. Commun Biol 4, 897 (2021). 

Photo Credit: Image of damselfish Chromis viridis swimming. Photo by Randall, J.E. from