The Life Cycle of a Fish: Part 1

Lesson Plan - Get It!

Audio:

Fish can be found in freshwater bodies of water like lakes and rivers, and saltwater bodies of water like the ocean.

There are many different kinds of fish all over the world. There are over fifteen thousand different species of fish! For example, clownfish and tuna are two different species of fish. The picture below shows twelve different species of fish. Even though there are so many different types of fish, all fish go through the same life cycle. In this lesson, you will learn about the beginning of the life cycle of a fish.

The first part of a fish’s life cycle is the egg stage. Fish lay their eggs in the water. The female fish will make a nest at the bottom of the water on the ground, on rocks or plants, or will even lay its eggs on the surface of the water. Female fish usually lay hundreds of eggs; some even lay thousands of eggs! Fish lay many eggs because most of the eggs will not survive. The eggs might be eaten, carried away by water, or if the temperature changes, the eggs will not survive. The more eggs a female fish lays, the better chance some of the eggs will survive. Below, you can see fish eggs:

The fish in the egg will begin to grow. First, its eyes will develop. Next, its tail will start to grow. Its tail will wrap around its head while it is still in the egg. Fish eggs that are found in cold water will take longer to hatch than fish eggs that are found in warmer water. Once the baby fish in the egg has fully developed eyes and a tail, it will hatch out of the egg. Below, you can see Saddleback Anemonefish guarding their eggs:

Once the fish has left the egg, it is in the larval stage. The larva (baby fish) will not know how to find food after it first hatches. It will need to eat the yolk sac that was once part of the egg it was in. The larvae (plural) will spend several days eating the yolk sac that is attached to their body. Once it has finished the yolk sac, it will be ready to eat plants and animals.

Once the fish starts searching for food, it is in the fry stage of its life cycle. This stage occurs during the first few months of a fish’s life. During this time, it will search for food. It may eat insects, small fish, algae, and plants. The type of fish it is will determine what it eats. For example, if the fish in the fry stage is a salmon, it may only be able to eat insects and plankton. Once the salmon grows into an adult fish, it will be able to eat larger fish, squid, shrimp, and eels. During this stage, the fish will still be very small.

The three stages of a fish's life cycle are the egg stage, the larvae stage, and the fry stage. Tell your parent or teacher what happens during each stage.

After sharing, move on to the Got It? section to show what you know about the fish life cycle.