Blue Whales Returning to Pre-Whaling Feeding Grounds

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The first known migration of blue whales from the coast of California to the Gulf of Alaska and areas off the coast of British Columbia since 1965 has been documented by scientists, suggesting that historical migration patterns are being established by these amazing marine mammals.

Researchers from NOAA’s Southwest Fisheries Science Center, Canada’s Department of Fisheries and Oceans, and the Cascadia Research Collective identified 15 cases of blue whales being observed in historical feeding grounds. By comparing photographs of blue whales taken since 1997 in the Pacific Ocean, researchers were able to match the pigmentation patterns and dorsal fin shapes of four whales previously seen off the coast of California with those observed in the Gulf of Alaska and off British Columbia.

Blue whales, thought to be the largest animal to have ever existed on earth, were hunted to near-extinction during commercial whaling activities during the early 1900s, and populations have never rebounded. Scientists studying them are still not certain why the blue whales are beginning to migrate from southern California to the north Pacific Ocean, although changing conditions in the ocean may have shifted krill, their primary food source, further north.

Blue whales reach lengths of nearly 100 feet, and are currently listed as endangered under the U.S. Endangered Species Act and are also on the red list of endangered animals of the International Union for the Conservation of Nature. An estimated 5,000 to 12,000 blue whales remain today, with approximately 2,000 (the largest population) off the west coast of the U.S..

The study is published in Marine Mammal Science, “Insights into the population structure of blue whales in the eastern North Pacific from recent sightings and photographic identifications.”

Image: ©John Calambokidis, Cascadia Research Collective