Theories why the Steller sea lion population declined by more than 80 percent during the 1980s include pollution, commercial fishing, and subsistence harvesting. The new study points instead to a climate regime shift–a natural event in the ocean’s climatic cycle–in the late 1970s that may be responsible for current regional population of about 40,000, compared with 235,000 in the 1970s.

The listing of the Steller sea lion (Eumetopias jubatus) as a threatened species under the Endangered Species Act in 1990 created new challenges for fisheries managers in the National Marine Fisheries Service and the North Pacific Fisheries Management Council. Managers must balance between two sometimes conflicting objectives: protecting and aiding the recovery of the Steller sea lion under the Endangered Species Act while at the same time providing for sustainable and economically viable fisheries under the Magnuson-Stevens Fishery Conservation and Management Act. => read more

The publication, entitled Bottom-up forcing and the decline of Steller sea lions in Alaska: assessing the ocean climate hypothesis by a team of scientists at the North Pacific Universities Marine Mammal Research Consortium, found that climate change affected water temperatures and ocean currents determining the abundance of available fish for the sea lion’s to eat. Changes in prey led to a decline in the sea lion population.

It seems a sudden ocean climate change 30 years ago changed today’s Alaska marine ecosystems, and may be a leading factor in the decline of Alaska’s endangered western stock of Steller sea lions. Source