Juvenile salmon ready to migrate to the ocean are called smolts. They make this journey mostly during the spring and summer. Ocean-bound juveniles may spend days, weeks or even months in estuaries feeding and adjusting their body chemistry before they enter the ocean, depending on the species and population. Once in the ocean, salmon stay there 1 to 5 years, depending on the species. During this time, they eat small fish and tiny animals called zooplankton.
Some salmon travel thousands of miles out into the north Pacific.
Others remain relatively close to shore. As adults, the salmon return to fresh water to spawn. Some, such as chinook salmon in Idaho, migrate more than 900 miles to their spawning grounds. Most return to the stream of their birth, although there is some straying. Straying ensures that salmon will colonize new areas if their old streams get destroyed by natural disasters.