Steelhead are the ocean-going form of rainbow trout.
Idaho steelhead are called summer run because they leave the ocean in August and September. When they arrive in Idaho, they spend the winter in deep river pools. In March to May they move from the Salmon and Clearwater rivers into smaller stream tributaries to spawn. Unlike salmon, a few steelhead may survive spawning to return to the ocean and migrate again.
Young steelhead live in Idaho streams for 1 to 5 years, although most spend only 2 to 3 years. They migrate to the ocean in May or early June and immediately swim into the deep ocean, where they live for 1 to 3 years.
Idaho steelhead are long distance swimmers and have been caught as far away as the Kuril Islands near the Asian coast in eastern Russia.