Idaho's steelhead are rainbow trout that, like salmon, migrate to the ocean and return to fresh water to spawn. They are classified as A-run or B-run, based on their size and ocean life history.A-run steelhead are usually found in the Snake and Salmon rivers. They return from the ocean earlier in the year, usually June through August, and they most often return after spending one year in the ocean. Because they return early in the year and because they usually come back after only one year in the ocean, average A-run steelhead weigh 4 to 6 pounds and are generally 23 to 26 inches long.The B-run steelhead most often return to the Clearwater River, but some return to tributaries in the Salmon River. These fish usually spend two years in the ocean, and start their migration to Idaho later in the summer or fall of the year, usually late August or September. Because of the extra year and the extra summer of growing in the ocean, they return as much bigger fish. Average B-run steelhead weigh between 10 and 13 pounds and are 31 to 34 inches long.Steelhead grow very large when they spend a third year in the ocean. These steelhead are usually larger than 37 inches and often weigh more than 20 pounds. The Idaho state record steelhead was 30 pounds and was caught in the Clearwater River in 1973.