ENVT - yellow-lined snappers Lutjanus lutjanus

In Focus: Why do fish school?

Fish schooling doesn’t mean books, papers, and a classroom. Instead, you get similar fish species banding together into a group that moves together in a synchronized manner. Schooling is a common behavior among our fish friends so it’s something you might have noticed during your snorkeling or diving adventures. Fish group together to increase their chances of survival, but how does schooling help?

Bigeye scad (Selar crumenopthalmus) at the Miniloc house reef. Photo by Macy Anonuevo
  1. Fishery loves company. Interacting with other fish means support for social functions. Grouping together makes it easier for the fish to talk to each other and so calms the fish. Studies have shown that the “feeling of belongingness” that fish get from schooling decreases stress and slows down their breathing.
  2. More heads are better than one. Getting a job done is much easier when there are more fish to help out. More eyes looking out for food means that there’s a bigger chance that you’re going to find it. With more fish involved, it’s easier to find prey, cover a wider area, and use up less time looking. The downside is that with more fish, there’s greater competition within the group once food is spotted.
  3. There’s plenty of fish in the sea. The line used by humans to soothe broken hearts also works on fish! Grouping together in a school makes finding the potential (fishy) love of your life much easier. Fish that migrate to spawn also conserve a lot of energy by swimming in a school instead of by themselves (see Advantage #4).
  4. E-fish-ciency. Swimming together decreases the drag caused by friction and water resistance. Swimming with a fish buddy means more fun and less energy used!
  5. Safety in numbers. The main reason why fish school is to protect themselves from predators. First, more fish in the group means more eyes looking out for potential trouble. Second, the big group of smaller fish looks like one big fish so they’re less likely to be attacked. And third, the many moving fish also disorient and distract a potential predator.
Yellow-lined snapper (Lutjanus lutjanus) at South Miniloc. Photo by Macy Anonuevo

In a fish-eat-fish world, many fish have decided not to face life alone. Although living in a group has its downsides, fish that live mostly in the open and have no hiding holes find safety in the company of others.

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