Changing Ocean Conditions Led To Decline In Alaska's Sea Lion Population

Studies by a team of scientists at the North Pacific Universities Marine Mammal Research Consortium revealed that 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.

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 publication, entitled Bottom-up forcing and the decline of Steller sea lions in Alaska: assessing the ocean climate hypothesis 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. Using interdisciplinary research methods was key in determining the root cause of the sea lion decline.

The need for such research is echoed in a related report: "Conserving Alaska's Oceans," prepared by Natural Resources Consultants. The report outlines 30 years of improved ocean conservation in the waters off Alaska with recommendations for future action. The report makes ten recommendations for continued improvement, including the need to address climate impacts, embrace the goals of ecosystem based fishery management, and the need to strengthen science programs to address future uncertainty.