The Salmon Life Cycle: a classroom guide

Salmon have one of the most incredible life cycles among fish. Unlike most fish, salmon live in two very different habitats—freshwater and saltwater. They begin their lives in cool, clear mountain streams, but migrate to the ocean where they spend much of their adulthood. Later, they make an epic journey back upstream to where they were born to lay eggs and start the cycle all over again.

Before we dive in: If you’re an educator planning to teach salmon or fish life cycles, great learning resources are key to deepening understanding! I think you and your students will love my salmon mini study, which you can also find within my complete Fish Unit (plus you’ll support my blog with your purchase! ❤️)

Life Begins in a Stream

A female salmon lays her eggs in a gravel nest in a freshwater stream. When the eggs hatch, the tiny fish are called alevins. They stay hidden among the gravel, sustained by the nutrients in their yolk sacs. Once the yolk sac is gone, they become fry and begin to feed and swim freely. As they grow, faint markings appear on their sides—these young fish are now called parr. They feed and begin defending small territories within the stream.

Journey to the Ocean

When the salmon are large and strong enough, they go through changes that prepare them for saltwater life. At this stage, they are called smolts. The smolts migrate downstream, swimming with the current, to the ocean. In the ocean, they will spend several years feeding on ocean prey and growing into adult salmon.

Returning Home

After maturing in the ocean, adult salmon return to the same stream where they were born—a journey that can cover hundreds of miles! This journey is especially challenging because the fish are swimming into the current. They must navigate around obstacles like fast-flowing water, log jams, and even waterfalls!

Once they reach their birthplace, the spawning adults lay and fertilize eggs. Female salmon lay their eggs in gravel nests, where they will hatch and begin the next generation of salmon. After spawning, most salmon die, but their bodies provide nutrients that enrich the stream ecosystem.

Examples of female and male adult spawning salmon.

The role of salmon

Salmon are a key part of both ocean and land ecosystems. In the ocean, they serve as food for animals like sharks and seals. When they return to freshwater, they feed predators such as bears, eagles, and otters. Even after death, their bodies nourish the soil and plants near the streams, making salmon vital to the health of the whole ecosystem.

Salmon in a stream. Photo by Line Knipst on Pexels.com

Salmon face many challenges throughout their long journey. Dams can block their migration routes, making it hard for them to reach their spawning grounds. Competition with invasive fish species can also reduce the number of young salmon that survive to adulthood. Human activities—like building cities and roads, farming, and mining—can damage salmon habitats by changing stream flow, increasing pollution, and removing trees that shade and cool the water. Climate change adds even more stress, warming rivers and oceans, altering streamflow patterns, and shifting ocean currents that salmon depend on for food and navigation.

To help, people are taking action. Fish ladders and fish-friendly dams allow salmon to swim upstream more easily. Habitat restoration projects work to clean up streams and remove barriers to migration. Scientists are also studying how to protect salmon as the climate changes, ensuring these remarkable fish can continue their journey for generations to come.

Study fish and salmon with Wild Earth Lab!

There’s no need to scramble to put together the perfect lesson on salmon or fish life cycles – I’ve already created it for you! This fish unit includes all the printable materials you need for studying fish life cycles, salmon, and more.