Published: May 2020
Revised: March 2021
Author(s): Chris L. Sato and Gary J. Wiles
The gray whale is a large baleen whale that feeds in shallow continental shelf waters and at offshore banks, where benthic (i.e., bottom-dwelling) invertebrate communities are concentrated. Gray whales are the only whale species known to feed extensively on benthic animals. They undertake the longest migration of any mammal, sometimes traveling more than 20,000 km round-trip annually in coastal waters.
Gray whales in the North Pacific are divided into two populations (or stocks) known as the Eastern North Pacific (ENP) and Western North Pacific (WNP) populations. Both populations were severely depleted prior to the mid-20th century by harvest during the whaling era. The ENP population migrates along the Pacific coast of North America between summer feeding grounds in the Bering, Beaufort and Chukchi Seas and wintering sites along western Baja California and the southern Gulf of California in Mexico, where mating and calving occur. This stock has recovered from the impacts of whaling, and was estimated at about 26,960 whales in 2016, when it was believed to exist at or near carrying capacity. However, the most recent estimate (made during the winter of 2019-2020) placed the population’s size at 20,580 animals, revealing a substantial decline of 23.7% since 2016. This population was federally delisted by the U.S. in 1994.
Within the ENP population, a small aggregation of about 232 individuals known as the Pacific Coast Feeding Group (PCFG) has been identified. These whales show regular fidelity during the summer and fall feeding season to waters along the coasts of northern California, Oregon, Washington, and Vancouver Island, British Columbia, and occasionally as far north as Kodiak Island, Alaska. Genetic testing indicates some differentiation from the greater ENP population, but PCFG whales likely interbreed with other ENP whales, and the PCFG is still considered a feeding aggregation of the ENP population.
The WNP population, which is federally classified as endangered by the U.S., primarily feeds in summer in the Sea of Okhotsk (mostly near the northeastern coast of Sakhalin Island, Russia) and off the southeastern coast of the Kamchatka Peninsula in the Bering Sea. Although historic records indicate that WNP gray whales migrated through the coastal waters of Japan and the Korean Peninsula to presumed wintering grounds off the coast of China, contemporary records of gray whales off Asia are rare. Abundance, calculated in 2016 to be roughly 271 to 311 individuals one year and older, remains far below pre-whaling numbers. Although considered genetically distinct from the ENP population, research since 2004 has detected some members of this population migrating to the Pacific coast of North America to feeding and wintering grounds traditionally used by the ENP population, and stock identity research is ongoing.
Gray whales face a number of known or potential threats such as entanglement in fishing gear and marine debris, ship strikes, human-generated marine sound, and climate change. These could adversely impact the WNP population because of its small size and precarious conservation status. The PCFG is also a concern due to its small size and the substantial level of uncertainty pertaining to its possible status as a separate stock under the Marine Mammal Protection Act.
The small WNP gray whale population is federally listed as endangered, and individuals have been seen in Washington waters. Research has indicated some genetic divergence in the PCFG from the ENP. However, these uncertainties do not justify any change in status at this time. Given these considerations and the threats and uncertainties described in this report, it is recommended that this species be retained as a state sensitive species in Washington. However, uplisting to a higher level of protection may be warranted in the future if continuing research determines that WNP whales regularly migrate through Washington’s waters and/or the PCFG is classified as a separate stock.
Sato, C. and G. J. Wiles. 2021. Periodic status review for the gray whale in Washington. Washington Department of Fish and Wildlife, Olympia, Washington. 32+ iii pp.
Draft documents are provided for informational purposes only. Drafts may contain factual inaccuracies and may not reflect current WDFW policy.