Steelhead are rainbow trout longer than 20 inches in length in the Snake River drainage below Hells Canyon Dam, the Salmon River drainage (excluding lakes and the Pahsimeroi and Lemhi rivers), and the Clearwater River drainage (excluding that portion above Dworshak Dam and lakes). Rainbow trout longer than 20 inches in length with the adipose fin clipped, as evidenced by a healed scar, are defined as steelhead in the Snake River from Hells Canyon Dam upstream to Oxbow Dam and in the Boise River from its mouth upstream to Barber Dam, during steelhead seasons.
Only steelhead with a clipped adipose fin (see Page 47), as evidenced by a healed scar, may be kept. These are hatchery fish that had their adipose fin removed as juveniles. All naturally produced steelhead with an intact adipose fin must be released because they are listed as “Threatened” under the Endangered Species Act (see Page 48). Some hatchery steelhead are not adipose fin clipped and must also be released.