Science Advisory Report  2012/057

Recovery potential assessment for the northern fur seal (Callorhinus ursinus) in Canadian waters

Summary

• Northern fur seals inhabiting the North Pacific comprise a single population;
• The species does not breed and rarely comes ashore in Canada.  However, fur seals undertake an extensive pelagic migration during the non-breeding season;
• During the pelagic migration, about 320,000 northern fur seals (30% of the population) winter along the west coast of North America (California to SE Alaska), with roughly one-third of them inhabiting Canadian waters during their peak abundance in May;
• Total abundance of northern fur seals has declined by approximately 14% from 1.3 million to 1.1 million over the last 30 years (3 generations).  The decreases occurred at the largest breeding area on the Pribilof Islands; abundance at other breeding areas has been stable or increasing;
• Peak seasonal abundance of northern fur seals in Canadian waters has declined by roughly 28% from 165,000 to 118,000 over the last 30 years (3 generations);
• The cause of the decline on the Pribilof Islands is unknown, but potential threats include changes in prey availability, climate change, entanglement in debris, oil spills and contaminants;
• Population viability analyses indicate that if recent declines in pup production on the Pribilof Islands continue, there is little chance (0.1-0.3%) the subpopulation will be extirpated within the next 100 years, but the risk escalates if the declines were to persist beyond the next century;
• The distribution objective for ensuring the security of northern fur seals in Canada is to maintain viable breeding sites, which are located outside of Canada, and to provide suitable habitat within Canada for foraging seals during their annual migration;
• Specific population objectives have not been established for fur seals in Canada, but will need to consider the abundance, population trend, and migration patterns of animals associated with each breeding site.  The large, declining Pribilof Island subpopulation currently has the greatest influence on abundance of seals in Canada, but the smaller, growing Bogoslof Island and large, stable Commander Island subpopulation have had increasing influence, whereas the distant breeding subpopulations in the Kuril Islands and Tyuleniy (Robben) Island have relatively little influence;
• Allowable harm limits have not been established for fur seals in Canada, but human-induced mortality is not considered to be a factor in the declines on the Pribilof Island, and human-induced mortality of fur seals in Canadian waters is currently negligible;
• Critical habitat in Canada has not been designated for fur seals, but historic data indicate the main wintering area was La Perouse Bank off SW Vancouver Island, which has been utilized predominantly during spring by adult females feeding mainly on herring;

This Science Advisory Report is from the Annual meeting of the National Marine Mammal Peer Review Committee (NMMPRC), 2011 held October 17 – 21, 2011. Additional publications from this process will be posted as they become available on the Fisheries and Oceans Canada Science Advisory Schedule.

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