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NGSS: Practice: Obtaining, Evaluating, and Communicating Information

Crosscutting Concepts: Cause and Effect

LS2.D: Social Interactions

CCSS: RI.5: Interpreting Text Features

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Why Fish Team Up

Do schools help fish save energy? A scientist investigates!

September 2025
By Alice Sun

© GABRIEL BARATHIEU/BIOSPHOTO

A colorful shape swirls through the ocean water. It moves like one enormous creature. But it’s made up of thousands of fish!

Groups of swimming fish like this one are called schools. Many other animals travel in groups too. The behavior helps animals survive. For instance, moving in groups can help animals find food and escape predators.

Yangfan Zhang is a biologist at Harvard University. He had another idea about how schools might help fish. Zhang thought fish swimming in schools might use less energy than fish swimming alone. To test his idea, he set up an experiment.

Swimming Together

About half of all fish species live in groups. Loose groups of fish that stay in one place are called shoals. Unlike shoals, schools of fish move together in whirling, tight-knit masses.

Fish have special body parts that help them swim together. A line of cells containing tiny hairlike structures runs down a fish’s body (see “Motion Detector,” below). These cells detect movements in the water. If one fish swims toward food or away from a predator, nearby fish can sense that movement and follow. That’s how schooling fish know where to go.

Swimming through the ocean is hard work. But when fish swim in schools, they block some of the water from pushing the fish behind them. Zhang wondered: Did that allow schooling fish to save energy?

Motion Detector

 RICHARD GRIFFIN/ALAMY STOCK PHOTO

A line of cells, called the lateral line, runs down a fish’s body. The cells detect small movements in the water, helping schools stay together.

Put to the Test

Zhang and a team of scientists studied a type of schooling fish called giant danio. The scientists put the fish in a looped tank filled with flowing water. “It’s like a racetrack for fish,” explains Zhang. The fish swam against the current. Some fish moved in groups. Others swam alone.

The team measured how much oxygen each fish took in through its gills as it swam. The scientists also took high-speed video of the fishes’ body movements. They used this data to figure out about how much energy the fish were using.

 COURTESY OF YANGFAN ZHANG


In the lab:

Yangfan Zhang placed fish in a tank. He measured how much energy they used while swimming in schools and while swimming alone.

Energy Savings

The scientists found that swimming in groups reduced the fishes’ energy use by more than 50 percent! The faster the school of fish swam, the more energy the fish saved.

There is still much to learn about schooling fish. Scientists wonder exactly how a fish’s movements in a group allow them to save energy. They also wonder how the results would be different outside a lab. “Every answer opens up 10 more questions,” says Zhang.

ISTOCKPHOTO/GETTY IMAGES

STAYING SAFE:

When fish move together in big groups, they’re harder for predators, like sea lions, to catch.

Animal Teams
Watch a video about how groups help animals survive.
Life Science
Animal Behavior

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