There are six stages of a salmon's life cycle: eggs, alevin, fry, smolt, adult, and spawners.
The salmon life cycle begins, and ends, as the spawning process in fresh water. The female chooses a site for her nest(s), called a redd, and builds one to several nests in the gravel with her tail. She then deposits her eggs into the nest and one or more males fertilize the eggs. The female then covers the eggs with gravel and repeats the process. Adult salmon guard the redd site until their death.
In late winter, eggs hatch from the redds. Young alevin in the gravel live off the nutritious yolk sac that hangs off their undersides for up to four months. Then they swim up from the gravel to start feeding on live prey. Some species head straight to the ocean as fry, while others remain in the stream for another year.
Next, the smolt stage occurs. The juvenile salmon swim downstream and undergo major physiological changes (smolting) while adapting to salt water in estuaries, where freshwater rivers meet the saltwater seas. Once in the ocean, Pacific salmon migrate to the North Pacific Ocean, travelling in schools. After one to seven years, depending on the type of salmon, they return to their home rivers to spawn where they had hatched.