The Snake River Wild Steelhead ESU includes all naturally spawned populations of Summer run steelhead (and their progeny) in the Snake River Basin.
The Upper Columbia River Wild Steelhead ESU includes all naturally spawned populations of steelhead (and their progeny) upstream from the Yakima River, Washington (above river kilometer 539), to the United States-Canada border and the Wells Hatchery stock of Summer run steelhead.
The Middle Columbia River Steelhead ESU includes all naturally spawned populations of steelhead in streams from above the Wind River, Washington, and the Hood River, Oregon (exclusive), upstream to, and including, the Yakima River, Washington. Excluded are steelhead from the Snake River Basin.
The Lower Columbia River Steelhead ESU includes all naturally spawned populations of steelhead (and their progeny) in streams and tributaries to the Columbia River between the Cowlitz and Wind Rivers, Washington (inclusive) and the Willamette and Hood Rivers, Oregon (inclusive). Excluded are steelhead in the upper Willamette River Basin above Willamette Falls and steelhead from the Little and Big White Salmon Rivers in Washington.