Steelhead Trout share the exact same genetics as Rainbows but differ in that they spend most of their lives in an ocean environment and only live in fresh water when they ascend rivers (usually the same river that they were spawned in) to spawn.
Because of the more nutrient rich environment of the ocean, they on average grow to a much larger size than what we call coastal Rainbows that live out their lives in fresh water. Steelhead are usually around 5 or 6 lbs when they are sexually mature and commonly reach sizes of 8-15 lbs.
Unlike Salmon who share the same streams, Steelhead commonly survive spawning and eventually swim back to the ocean to again return to spawn the following year. Steelhead only live in waters that are tributaries the Pacific ocean and can be found from the northern edge of Baja, Mexico to Kamchatka Russia.
Being that the southern most range of Steelhead experiences unreliable water/spawning conditions the only reliable annual spawning runs exist from approximately the San Lorenzo River in central California, north along the Pacific Coast to Alaska and then southeast to Kamchatka peninsula in Russia.
For many fly fishermen Steelhead are a bucket list fish, and for those who have the opportunity to fish for them on a regular basis, they are a passion.