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Swim bladder

Adapted from Wikipedia · Explorer experience

Labelled diagram showing the parts of a fish's swim bladder, which helps the fish stay at the right depth in water.

What is a Swim Bladder?

A swim bladder is a special gas-filled organ inside most bony fish. It helps the fish stay at the right depth in the water without having to swim all the time, which saves energy.

Fish can change the amount of gas in their swim bladder. This makes them lighter or heavier, so they can move up or down easily in the water.

Why is it Important?

The swim bladder is very useful for fish. It helps them stay steady and turn quickly. It can also help fish make or hear sounds underwater. This is why sonar equipment can find fish so well.

Fun Facts

Scientists think the swim bladder is related to the lungs of land animals. Not all fish have swim bladders. Fish like sharks and rays must swim all the time to stay in one place because they do not have them.

The swim bladder can also help scientists learn about fish numbers by using sound equipment. This helps protect fish and the environment.

Images

Diagram showing the swim bladder of a Ruddy fish, which helps it control its depth in water.
A detailed scientific drawing showing the internal structure of a small fish called a bleak.
Diagram showing how fish use gas bladders to control their depth in water.
An artistic illustration showing how a Lepidosiren fish uses its air bladder like a lung to breathe.

Related articles

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Sonar

This article is a child-friendly adaptation of the Wikipedia article on Swim bladder, available under CC BY-SA 4.0.

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