Science Advisory Report 2008/047
Population Assessment: Steller Sea Lion (Eumetopias jubatus)
Summary
- DFO has conducted 10 province-wide aerial surveys since the early 1970s to monitor Steller sea lion populations. Beginning in 1994, the surveys have been conducted at 4-year intervals as part of an international range-wide survey that extends from California to Alaska to Russia. Surveys are timed to coincide with the end of the breeding season so as to provide an estimate of pup production, as well as counts of juveniles and adults (non-pups).
- The abundance of Steller sea lions in B.C. has increased at an overall rate of 3.5% per year since the early 1970s. Non-pup numbers were stable until the early 1980s, but subsequently increased at 5.0% per annum. Pup numbers were stable until the mid-1980s, but subsequently increased at 7.9% per annum.
- During the most recent survey in 2006, a total of 19,818 sea lions were counted in B.C. This included 4,118 pups and 15,700 non-pups (7,171 on rookeries and 8529 on non-breeding haulout sites).
- The counts from aerial surveys represent minimum abundance because, except for pups, some animals would be foraging at sea and missed. Based on the estimated pup production and a ranged of multipliers derived from life table statistics, it was calculated that at least 20,000 and as many as 28,000 Steller sea lions currently inhabit coastal waters of B.C.
- Abundance of Steller sea lions has also increased in recent years at neighboring rookeries in SE Alaska and Oregon (the species does not breed in Washington). This contrasts sharply with the western stock of Steller sea lions (Gulf of Alaska, Bering Sea, Aleutian Islands, and Russia), which has declined by 80% since the 1970s and been designated as endangered.
- Recovery of Steller sea lion populations in the eastern portion of range has renewed concern over their impact on fishery resources and their role in the ecosystem.
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