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.
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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!
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.
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.
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.
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.
Shoaling and Schooling Fishes 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.
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