NOAA's National Marine Fisheries Service (NMFS) is issuing a final determination to list the Southern Resident killer whale distinct population segment (DPS) as endangered under the Endangered Species Act of (ESA) 1973. Following an update of the status review of Southern Resident killer whales (Orcinus orca) under the ESA, NMFS published a proposed rule to list the Southern Resident killer whale DPS as threatened on December 22, 2004. After considering public comments on the proposed rule and other available information, we reconsidered the status of Southern Residents and are issuing a final rule to list the Southern Resident killer whale DPS as an endangered species. The prohibition on take of an endangered species will go into effect at the time this final rule is effective (see DATES).