Trout Unlimited v. Lohn

Under the Endangered Species Act (ESA), an agency had to identify a species, subspecies, or distinct population group (DPU) before it could list it as endangered or threatened. A DPU, or evolutionarily significant unit (ESU), had to be reproductively isolated from other population units and represent an important piece of the species’ evolutionary legacy. In 2005 the National Marine Fisheries Service (NMFS) (defendant), based on scientific research demonstrating that hatchery stocks were not reproductively isolated or significantly distinct from natural populations in the fishery, issued a policy that combined natural and hatchery salmon and steelhead populations in the upper Columbia River within one ESU. The NMFS stated that hatchery fish would be considered in the context of conserving natural populations (i.e., the varied effects of hatchery fish on natural fish would be considered in assessing the threat to the ESU’s survival). The NMFS listed the ESU as threatened. Trout Unlimited (plaintiff) filed a petition challenging the policy, arguing that natural fish alone should be included because they were threatened by hatchery fish. Trout Unlimited also argued that combining the natural and hatchery fish resulted in the ESU being downgraded from endangered to threatened. The Building Industry Association of Washington (the building association) intervened, arguing that the NMFS’s listing policy was invalid under the ESA because it permitted consideration of the effects hatchery fish might have on the ESU in its listing decision. The district court granted Trout Unlimited’s motion for summary judgment, and the NMFS appealed.