Scientists have documented the first known migration of blue whales from the coast of
California to areas off British Columbia and the Gulf of Alaska since the end of commercial
whaling in 1965.
In the scientific journal Marine Mammal Science, researchers from Cascadia Research
Collective in Washington state, NOAA’s Southwest Fisheries Science Center in California, and
Canada’s Department of Fisheries and Oceans identified 15 separate cases where blue whales
were seen off British Columbia and the Gulf of Alaska. Four of the whales were identified as
animals previously observed off the coast of California, suggesting a re-establishment of a
historical migration pattern.
Researchers made this identification by comparing photographs of blue whales taken in
the north Pacific Ocean since 1997 with a library of nearly two thousand photographs of blue
whales off the West Coast. A positive match was determined based on pigmentation patterns in
skin color and shape of the dorsal fin.
Blue whales were severely depleted during commercial whaling activities during the
early 1900’s in the north Pacific and along the West Coast as far south as Baja California.
Formerly large populations of blue whales in the north Pacific never rebounded after commercial
whaling ended while those animals off southern California have apparently fared much better.
Scientists are still not certain exactly why blue whales are now beginning to migrate from
southern California to the north Pacific Ocean although changing ocean conditions may have
shifted their primary food source of krill further north.
Blue whales are thought to be the largest animal ever to have existed on earth, reaching
lengths of nearly 100 feet. They were nearly hunted to extinction throughout the world and are
currently listed as endangered under the U.S. Endangered Species Act and as endangered on
the red list of the International Union for the Conservation of Nature. There are an estimated
5,000 to 12,000 animals remaining today, with the largest population of approximately 2,000 off
the U.S. West Coast.
On the Web:
Video and Photos: http://swr.nmfs.noaa.gov/media/blue_whale.htm
Marine Mammal Science article: http://www.cascadiaresearch.org/MMS-AK-BC-BM-09.htm
More information about blue whales:
http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/bluewhale.htm