Fish Facts: Lesson for Kids

You may have seen them in the ocean, in an aquarium…or on your dinner plate! Fish are important and fascinating animals. This lesson will teach the basics of what makes a fish, a fish.

Fish Features

Fish are different sizes, shapes, and colors, but they all have some things in common. All fish are vertebrates, meaning they have backbones (though not all ‘backbones’ are made of bone- we’ll get to that in a minute.) They all have skeletons that give them their shape and protect their internal organs. Many fish, like goldfish and tuna, have bony skeletons. Others have skeletons made of cartilage, which is the flexible stuff that makes up the tip of your nose.

The whale shark is the largest fish in the world. It is longer than a school bus!
whale shark

Fish need gills to breathe in the water. Gills are slits on each side of the head that take oxygen from the water, where it then travels into the fish’s blood. A few kinds of fish, called lungfish, can breathe air at the surface.

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Fish have fins that help them balance and swim. Most fish have strong tail fins that push them through the water, but you may also see fins on their backs, sides, and bellies. Some fish have special fins that let them walk short distances on land.

Most fish are covered in tough scales that help protect their skin. Sharks have special scales that look and feel like tiny teeth.

Where Do Fish Live?

All fish live in water, but their homes are still very different. Some live in freshwater habitats, like lakes and rivers, while others live in the salty ocean. Fish that live in bays get a mix of freshwater and saltwater. You can find fish in deep, cold water, but also in warmer and shallower water.

Fish don’t always stay in the same place. They might migrate, meaning they travel long distances to find food or mates. Some fish, like salmon, even move back and forth between freshwater and saltwater.

Fish may live alone, or in groups called schools. Some schools have hundreds of fish.

These fish, called permits, swim through the ocean in schools.
school of fish

What Do Fish Eat?

Fish can live on all sorts of different foods. Some only eat plants or plant-like algae, while others eat meat. If their home is surrounded by trees, they may eat fruits, nuts, and bugs that fall off the branches.

Some fish use cool tricks to get their food. The archer fish spits water at bugs to knock them off branches. Some fish even jump clear out of the water to get their food! Great white sharks have been filmed jumping out of the water to catch seals.

Baby Fish

Fish usually have many tiny babies at once. They may be born live or hatch from eggs. Baby fish usually live on their own right after birth, but a few stay with their parents.

Baby salmon develop inside their eggs.
salmon eggs

Fish Populations

You may be wondering how many fish there are in the world. The answer is, too many to count! However, scientists do try to keep track of fish numbers. Fish may be hurt by pollution or overfishing, so it is important to know if they populations are healthy or not.

Lesson Summary

Fish are vertebrates that live in water all over the world. Different kinds of fish are found in different types of water. They may eat algae, plants, or other animals. Some fish give birth to live young, while others lay eggs. Nobody knows exactly how many fish there are in the world, but scientists keep track of them to know if their populations are healthy.


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