Western gray whales were hunted by aboriginal people in the northern part of their range since prehistoric times but to an unknown extent (Mitchell, 1979). They were taken by Japanese hand-harpoon whalers in the Sea of Japan since at least the 16th century, and by net whalers on the Pacific coast in the 17th to 19th century (Omura 1984, 1988). Western gray whales were also taken by European and American whalers, mainly in the Okhotsk Sea, from the late 1840s to perhaps the start of the 20th century (Henderson 1984), and by Russian steam whalers on the Russian far eastern coast at the end of the 19th century (Andrews 1914, Weller et al. 2002). Quantitative information is scarce, but it is possible that the subpopulation was already depleted by the start of modern whaling at the end of the 19th century. During 1890-1966 an estimated 1,800 – 2,000 gray whales were taken off the Korea peninsula and Japan (Kato and Kasuya 2002). Apart from the main grounds off southeastern Korea, whales were also taken in the Yellow Sea in the early part of this period. Occasional catches are recorded from China during 1916-58 (Zhu and Yue 1998). It is not known whether any whales have been taken by the Democratic People’s Republic of Korea.
Three western gray whales, all females, were fatally entangled in net-traps on the Pacific coast of Japan in 2005 (Kato et al., 2006). Subpopulation projections show that if this level of mortality continues, the subpopulation would decline towards extinction (Cooke et al. 2006, IWC 2007). Most recently, a female yearling (9.1 m) was killed in YoshihamaBay, Sanriku, Japan on 19 January 2007. The stranding of a dead western gray whale in Japan with a hand harpoon lodged in it of the kind used by porpoise hunters (Brownell and Kasuya 1999) is of concern, as is the finding of gray whale meat on domestic whale meat markets on the Pacific coast of Japan (Baker et al. 2002). Incidental catches of cetaceans in the extensive coastal net fisheries off southern China are also of concern (Zhou and Wang 1994).
The substantial nearshore industrialization and shipping congestion throughout the migratory corridors of this subpopulation represent potential threats by increasing the likelihood of exposure to ship strikes, chemical pollution, and general disturbance (Weller et al. 2002).
Offshore gas and oil development in the OkhotskSea within 20 km of the primary feeding ground off northeast SakhalinIsland in the OkhotskSea is of particular concern. Activities related to oil and gas exploration, including geophysical seismic surveying, pipelaying and drilling operations, increased vessel traffic, and oil spills, all pose potential threats to western gray whales. Disturbance from underwater industrial noise may displace whales from critical feeding habitat. Physical habitat damage from drilling and dredging operations, combined with possible impacts of oil and chemical spills on benthic prey communities also warrants concern (Reeves et al. 2005)