Distinct population segment

A distinct population segment is the smallest division of a taxonomic species permitted to be protected under the U.S. Endangered Species Act. Species, as defined in the Act for listing purposes, is a taxonomic species or subspecies of plant or animal, or in the case of vertebrate species, a distinct population segment (DPS).The criteria for designation of a population or group of populations as a DPS was most recently articulated in a 1996 joint USFWS-NMFS policy (61 FR 4722: February 7, 1996):The Fish and Wildlife Service's Listing and Recovery Priority Guidelines (48 FR 43098; September 21, 1983) generally afford DPS's the same consideration as subspecies, but when a subspecies and a DPS have the same numerical priority, the subspecies receives higher priority for listing. The Services will continue to generally accord subspecies higher priority than DPS's.In consideration of Pacific salmon for listing under the Act, NMFS has relied on the evolutionarily significant unit (ESU) concept and previous developed a policy on the definition of species under the Act (56 FR 58612– 58618; November 20, 1991). The policy applies only to species of salmonids native to the Pacific. Under this policy, a stock of Pacific salmon is considered a DPS if it represents an evolutionarily significant unit (ESU) of a biological species. A stock must satisfy two criteria to be considered an ESU: (1) It must be substantially reproductively isolated from other conspecific population units; and (2) It must represent an important component in the evolutionary legacy of the species. The 1996 joint policy considers the 1991 NMFS policy on Pacific salmon to be consistent with the joint policy, being a detailed extension of it. The joint policy further states that NMFS will continue to exercise the 1991 policy with respect to Pacific salmonids.Waples, R.S. 1991. Definition of 'species' under the Endangered Species Act: Application to Pacific salmon. U.S. Dept. Commerce, NOAA Tech Memo. NMFS, F/NWC-194.