Recovery Plan for the Steller Sea Lion. Eastern and Western Distinct Population Segments( Eumetopias jubatus)

摘要

The Steller sea lion (Eumetopias jubatus) was listed as a threatened species under the ESA on April 5, 1990 (55 FR 126451) due to substantial declines in the western portion of the range. At the time of listing, the overall abundance of sea lions in the eastern portion of the range (in southeastern Alaska and Canada) was increasing at approximately 3% per year. Critical habitat was designated on August 27, 1993 (58 FR 45269) based on the location of terrestrial rookery and haulout sites, spatial extent of foraging trips, and availability of prey. In 1997, based on demographic and genetic dissimilarities, NMFS designated two distinct population segments (DPSs) of Steller sea lions under the ESA: a western distinct population segment (DPS) and an eastern DPS (62 FR 24345, 62 FR 30772). Due to persistent decline, the western DPS was reclassified as endangered, while the increasing eastern DPS remained classified as threatened. Through the 1990s, the western DPS continued to decline. The western population showed an increase of approximately 3% per year between 2000 and 2004. This was the first recorded increase in the population since the 1970s. However, the most recent available data from incomplete non-pup surveys in 2006 and 2007 suggest that the overall trend for the western DPS, through 2007, is either stable or slightly declining. Data indicate there are significant trend differences amongst sub-regions within the western DPS. Based on 2004-2005 data, the total population size of western Steller sea lions in Alaska is estimated to be approximately 45,000 animals. The current (as of 2005) population of Steller sea lions in Russia (part of the western DPS) is estimated to be about 16,000. The eastern DPS was estimated to number between 46,000 and 58,000 animals in 2002, and has been increasing at approximately 3% per year since the late 1970s (Pitcher et al. 2007).