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Why Are Steller Sea Lions Disappearing?

Since 1980, the world population of Steller sea lions has dropped dramatically, where some populations have dropped by up to 75 percent. Possible reasons for this include parasites and disease, killer whale predation, and competition with humans and other species for food. Climate change, pollution, entanglement in marine debris, and incidental and intentional take by humans may also be involved.
Visit our Steller sea lion AquaFacts

Steller Sea Lions Credit: Andrew Trites

Sea Lion Research Credit: Margaret Butschler

Other Species With
Changing Populations

Alaskan harbour seal populations have also declined, northern fur seals are depleted and similar declines have been reported in seabird breeding colonies. In British Columbia, Steller sea lion numbers appear stable, but harbour seal populations have increased rapidly. Further south, striking increases are being observed in the range and abundance of elephant seals and California sea lions.

The Research Beginnings

In 1993, a large scale research plan was developed by the Marine Mammal Research Consortium to study marine mammal interactions in the North Pacific. This project also explores possible causes for declining Steller sea lions populations through field, captive and laboratory studies. The Vancouver Aquarium’s Marine Mammal Department is helping with research to analyze the nutritional stress hypothesis.

Metabolic Dome
Sea Lion Research

Research At The
Vancouver Aquarium

In 1993, five Steller sea lions came to the aquarium, a sixth, Sade, came to the aquarium in 1994 as a rescue animal. There are currently 4 Stellers at the Aquarium and 4 at the open water site. 

What Does The
Research Explore?

Another batch of five pups arrived in 2000 to further explore the "nutritional stress" hypothesis, the leading theory to explain the decline in Steller sea lions in the wild. This hypothesis proposes that they are declining due to a change in the type, quantity or distribution of their prey. These studies are providing information that is unobtainable from wild animals.

Sea Lion Research

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