The National Marine Fisheries Service (NMFS) announced (pdf) that it will not list the Gulf of Mexico population of sperm whales (Physeter macrocephalus) as an endangered or threatened distinct population segment (DPS) under the Endangered Species Act (ESA).

Sperm whales were originally listed as endangered under the precursor to the ESA—the Endangered Species Conservation Act of 1969—and remained on the list of threatened and endangered species after the passage of the ESA in 1973. In December 2011, NMFS received a petition to list the Gulf of Mexico population as a threatened or endangered DPS under the ESA. NMFS determined (pdf) in March 2013 that the petition presented substantial information indicating that listing the Gulf of Mexico population as a DPS may be warranted, and so undertook a status review of the species.

Ending the inquiry this week, NMFS determined that listing the Gulf of Mexico population as a DPS is not warranted. As the basis for its determination, NMFS cited its conclusions that the Gulf of Mexico population did not constitute a discrete population, that it did not differ markedly from other populations of sperm whales in its genetic characteristics, that loss of the population would not result in a significant gap in the species’ range, and that the Gulf of Mexico population did not occupy an ecological setting unusual for the species.