The court of appeals affirmed a judgment of the district court. The court held that the definition of “species” in the Endangered Species Act did not require an agency to place interbreeding steelhead and rainbow trout in the same distinct population segment.
The National Marine Fisheries Service (NMFS) listed steelhead trout, a type of Pacific salmon, as a threatened species in California’s Central Valley. NMFS defined steelhead trout as a distinct species under the Endangered Species Act (ESA), separate from rainbow trout, another type of Pacific salmon that breeds with and looked similar to steelhead. That was a departure from prior NMFS policy of classifying interbreeding Pacific salmon as a single species.
