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It’s the season of new backpacks, pencils and protractors for the millions of students going back to school this fall. Kids will soon meet their teachers and file into their classrooms with their peers, moving with the crowd like fish in a school!

A group of fishes, potentially of different species, that loosely cluster together for social reasons is called a shoal. A group of fish, most likely of the same species, swimming in a coordinated manner is called a school.

A group of large trevally fish cruise through Wild Reef.

Shoaling fish can shift into a disciplined and coordinated school, then shift back to an amorphous shoal within seconds. Those shifts are triggered by changes of activity from feeding, mating, resting, traveling or avoiding predators.

It’s estimated that about 25% of fishes shoal all their lives, and 50% shoal part of their lives. There are many benefits to sticking with a group. Let’s explore why they say there’s strength in numbers!

A small, tightly-packed school of silver fishes.
Sandbar sharks have a classic shark profile with a triangular dorsal fin and a streamlined body shape designed for constant movement.

Protection from predators

Individuals gathered make themselves seem like one large, intimidating creature that can scare off a predator. It can also be difficult for a predator to single out a fish among many that look nearly identical. A school’s mesmerizing and precise turns and twists — all swimming in the same direction, at the same speed at the same time — can confuse a bigger animal looking for a meal.

A group of orange anthias swim together in a rocky habitat. Their sharply forked tails and bright orange fins and bodies make for a beautiful shimmering effect as they swim closely grouped together.

Find food faster

Shoaling or schooling can also help fishes find food. Many eyes and noses to scout for a meal are better than one. Some small schooling fishes, like herring and anchovies, are called “forage fish” that filter feed with open mouths to catch miniscule plankton, sometimes in synchronized grid formations to not miss a morsel. The forage fishes themselves can also become meals for larger fishes, seabirds and marine mammals.

A teeming school of little yellow-striped fish.
Tiny silver fishes school together

More efficient swimming

Experts theorize that fishes may save energy swimming in groups. The uniformity of spacing and size when the same species of fish schools can improve hydrodynamic efficiency, much like how a bicyclist can aerodynamically benefit from the draft of another in a group.

Malawi sandsifters have long, trailing fins on their backs and bellies.

Locate a mate

Gathering together increases the chances for individual fish to find a potential mate. Forage fish often make great migrations between their spawning, feeding and nursery grounds, so traveling near a mate can reduce the energy it would take to migrate and find a mate alone.

A school of trevally fish rush towards the camera.
School of yellow and light blue fish swimming over coral in The Bahamas

Shoaling and schooling fish at Shedd

While you’re exploring Wild Reef, make sure to look up! A school of dazzling, silver false herring swirls overhead. You may also see schools of golden trevally trailing sharks, looking for scraps of food that the sharks may have let slip by them.

As you take in the beauty of Caribbean Reef, spot the shiny Atlantic spadefish schooling together as they traverse the diverse coral reef habitat.

The pictus catfish in Amazon Rising school in large groups, swimming in tandem as a large mass.

Upon entering Amazon Rising, spot the freshwater pictus catfish grouping together with their exceptionally long barbels.

Finally, your first stop in Underwater Beauty will be to see the metallic giant danio magically shoaling in their cylindrical habitat.

A school of small silvery fish.