Steller sea lion counts, Gulf of Alaska (1956-2014)

In November 1990, the NMFS listed Steller sea lions as “threatened” range-wide under the U.S. Endangered Species Act (55 Federal Register 49204, November 26, 1990) in response to a population decrease of 75% during the previous 15-year period in the core of their range in the Aleutian Islands and Gulf of Alaska. By 1997, two population stocks were identified, based largely on genetic differences, but also on regional differences in morphology and population trends (Bickham et al., 1996; Loughlin, 1997). The western stock, which breeds and gives birth on rookeries from 144 W (approximately at Cape Suckling, just east of Prince William Sound, Alaska) westward to Russia and Japan, was listed as “endangered” in June 1997 (62 Federal Register 24345, May 5, 1997) because of persistent 5% per year declines through the 1990s. The eastern stock, which occurs from Southeast Alaska southward to California, remained classified as threatened in 1997, but has been increasing at 3% per year since at least the mid-1970s (Pitcher et al., 2007), and was removed from the list of threatened species in November 2013 (78 FR 66140) . The Steller sea lion Recovery Plan (NMFS, 2008) contains recovery criteria for de-listing both stocks (removal from the list of threatened and endangered species) and down-listing the western stock from endangered to threatened. NMFS (2008) also assessed the threats to recovery for both stocks, and determined that there were no threats to recovery for the eastern stock , while for the western stock, nutritional stress resulting from competition with fisheries or environmental variability, and predation by killer whales were listed as potentially high threats to recovery, and effects of contaminants or pollutants was listed as a medium threat (largely due to significant data gaps).

Population assessment for Steller sea lions in Alaska is currently achieved by aerial photographic surveys of pups and non-pups (adults and juveniles at least 1 year-old) during the breeding season (June-July). Abundance trends are estimated using the methods of Johnson and Fritz (2014). These data represent counts of Steller sea lions in the Gulf of Alaska between 1956 and 2014 in the eastern GoA, central GoA and western GoA regions (NMFS SSL regions 6, 7, 8). Data include temporal and spatial details of the counts and are divided into counts of pups and non-pups. These data belong to the National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA. Please contact and attribute this group when the data are used.