BC sea lion cruise reports big change

Dr. Trites led a research cruise in early July along the British Columbia coastline to collect Steller sea lion diet samples (scats), identify US born sea lions (from brands), document the incidence of entangled sea lions, and record the establishment of new breeding areas. The over-arching goal has been to document the factors that allow sea lion populations to grow — to better understand why their counterparts in the Gulf of Alaska, Bering Sea and Aleutian Islands have declined.

Andrew Trites and team

The researchers sailed from Port Hardy along the central coast to the Alaska border and traveled down the east coast of Haida Gwaii before crossing the open ocean to Vancouver Island. 

They noted fewer entangled sea lions than in past years, and had many encounters with killer whales — including a pod of transient killer whales attacking harbor seals next to a beach full of Steller bulls.

Branded sea lions from Alaska and Oregon were photographed to contribute to a larger data base used to estimate birth and death rates and establish the movements of sea lions between geographic regions.

Andrew Trites and team

The most noteworthy observation was the continued expansion of sea lions and the establishment of new breeding colonies.

British Columbia used to have four breeding areas for Steller sea lions, but one was extirpated by culling (the Sea Otter Group) and the other three breeding populations were reduced to low numbers.  Things did not turn around for Steller sea lions in the late 1980s and early 1990s — but they have increased at an exponential rate ever since. 

Andrew Trites and team

The first sign of sea lion expansion was noted in 2000 when pups were born on one of the extirpated breeding islands after an absence of over 60 years (Virgin Rocks).  This was followed soon after by the establishment of a second new breeding colony in Haida Gwaii (Garcin Rocks). 

This summer’s research cruise confirmed that both new sites have increased since the last survey.  However, the researchers also discovered pups being born at three additional sites along the BC central coast, but it is too early to know whether their numbers will grow to the point of being secure established breeding colonies.  Only time and additional field trips will tell.


Dr. Andrew W. Trites is the director of the Marine Mammal Research Consortium at U.B.C.




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