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What Is the Function of The Swim Bladder? With Infographic

Lindsey Stanton Profile Picture

By Lindsey Stanton

fish swim bladder in hands

While most fish that we keep in our homes are not all that big, they do certainly have quite an interesting anatomy. One of the things that you might be interested to know about is how fish, or some of them, control their buoyancy, or in other words, how they sink deeper and float higher up.

This is where an organ known as the swim bladder comes into play. Let’s talk about what exactly the swim bladder is and how it works.

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What Is A Swim Bladder?

fish anatomy
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Most bony fish have swim bladders, but many cartilaginous fish do not. The swim bladder is also known as the air bladder, fish maw, or gas bladder as well. The swim bladder is located in the center mass of the fish and is a derivative of the digestive cavity of the fish.

It is a buoyancy organ, in simplest terms. So, in layman’s terms, the swim bladder is an organ used for buoyancy that most bony fish possess.

What Is The Purpose Of A Swim Bladder?

function of swim bladder
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As you can probably guess, since the swim bladder is the buoyancy organ of a fish, its purpose is to help fish regulate their depth. Yes, some fish simply use their fins to swim up and down in the water column, but this uses quite a bit of energy that fish sometimes just don’t have to spare.

Well, the swim bladder allows some fish to adjust their depth in the water using nothing more than some gas. The swim bladder is usually filled with oxygen but can contain other gases as well.

In other words, if a fish wants to sink deeper down, it will empty some of the oxygen from the bladder, thus making the fish less buoyant. If the fish wants to rise to the surface, or just rise higher in the water, it will inflate the swim bladder with more gas to increase buoyancy.

It is also shown that in some fish if the oxygen in the water is at a low level, the bloodstream of the fish may draw on the oxygen in the swim bladder to stay properly oxygenated.

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Final Thoughts

If you were wondering how most fish sink and rise in the water column so rapidly, the swim bladder is how it is done. It’s actually quite a simple organ, one that most fish have and use to help make their daily lives just a little bit easier.

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Featured image: Malgorzata Surawska, Shutterstock

Lindsey Stanton Profile Picture

Authored by

Lindsey discovered her passion for fish keeping after a junior high school field trip to the Shedd Aquarium in Chicago. Prior to becoming Editor-in-Chief of It's a Fish Thing, Lindsey studied marine biology at the University of California-Santa Cruz. She loves goldfish, tetras, and mystery snails, and recently began experimenting with a saltwater aquarium.

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