Movements of Gray Whales between the Western and Eastern North Pacific

Gray whales (Eschrichtius robustus) are presently recognized as two populations in the North Pacific. The eastern North Pacific (ENP) population was removed from the U.S. List of Endangered and Threatened Wildlife in 1994 and is currently estimated to number approximately 19,000 individuals. In contrast, the western North Pacific (WNP) -population is estimated to be about 150 individuals and is redlisted by IUCN as Critically Endangered. The ENP population ranges from wintering areas off Baja California, Mexico, to summer feeding areas in the Bering, Beaufort, and Chukchi Seas. The WNP population feeds in the Okhotsk Sea off Sakhalin Island, Russia, and in nearshore waters of the southeastern Kamchatka Peninsula (southwestern Bering Sea). Little is known about the current migratory route(s) and wintering area(s) in the WNP, but historic evidence indicates that the coastal waters of eastern Russia, the Korean Peninsula and Japan were all part of the migration corridor and that areas in the South China Sea were used as wintering grounds.

In this study (Weller et al. 2012),The previous link is a link to a Non-Federal government web site. Click to review NOAA Fisheries Disclaimerwhich was recently published as the feature article in the journal Endangered Species Research, researchers from the SWFSC in collaboration with colleagues from Canada, Mexico, Russia and the U.S. were able to photographically track some whales in the WNP migrating to areas in the ENP off the coast of North America (Vancouver, California, Mexico) during the winter. Although these inter-area matches have provided new insights on trans-Pacific gray whale movements and population mixing, genetic studies conducted by SWFSC researcher Dr. Aimee Lang have demonstrated significant differentiation between the two populations (Lang et al. 2011).

Past and present winter observations of gray whales off Japan and China (Weller and Brownell 2012), however, clearly suggest not all gray whales identified in the WNP migrate to a common wintering ground. With this in mind, gray whale researchers from SWFSC have their sights set on building a collaborative project with colleagues from China to try and address the mystery of where WNP gray whales spend the winter.

Gary Whale Team
Western Gray Whale Research Team. Photo by David Weller.
Gray Whale Paper