Eschrichtius robustus (western subpopulation)

This subpopulation of Eschrichtius robustus (Lilljeborg, 1861), called the western gray whale, is probably genetically isolated from the only other extant subpopulation, known as the eastern gray whale (LeDuc et al. 2002); the ranges do not appear to overlap (Blokhin 1996). It is listed separately for conservation and management purposes (see separate listing for the global species).

The western gray whale summers in the OkhotskSea, mainly off the northeastern coast of SakhalinIsland (Russian Federation). There are also occasional sightings off the eastern coast of Kamchatka (Russian Federation) and in other coastal waters of the northern OkhotskSea (Vladimirov 1994, Weller et al. 1999). Its migration routes and wintering grounds are poorly known, the only recent information being from occasional records on both the eastern and western coasts of Japan (Kato et al. 2006) and along the Chinese coast (Zhu and Yue 1998). Until 1966, there was a whaling ground off Ulsan (southeastern KoreaPeninsula), where whales were taken during November to April, with two peaks (in December/January and March/April), suggestive of south- and northbound migrations respectively through the Sea of Japan (Kato and Kasuya 2002). However, no gray whales have been recorded in the Korean whaling grounds since 1968. The great majority of recent Japanese records are on the Pacific side, suggesting that this is now the more important migration route. The few modern records from China are scattered along virtually the entire Chinese coast from the northern Yellow Sea to the HainanStrait in the south (Zhu and Yue 1998). The calving grounds are unknown but may be around HainanIsland, this being the southwestern end of the known range (Brownell and Chun 1977).

Western gray whales were thought to be extinct as recently as 1972 (Bowen 1974), but a small number are now known to survive (Berzin 1974, Weller et al. 2002); the best estimate for 2006 is 113-131 animals, of which 26-35 are reproductive females, based on an analysis of photo-identification data (Cooke et al. 2006). The figures include adjustments for the photo-identified whales that are likely to have died and for the estimated number of living whales that have yet to be catalogued. In the absence of additional new mortality in excess of the estimated rate over 1994-2004, the population size is projected to increase at 2-4% per annum (Cooke et al. 2006). However, even a very small number of additional annual female deaths will cause the subpopulation to decline.

The main feeding habitat of this subpopulation is the shallow (5-15 m depth) shelf of northeastern SakhalinIsland, particularly off the southern portion of Piltun Lagoon, where the main prey species appear to be amphipods and isopods (Weller et al., 1999).  In some years the whales have also used an offshore feeding ground in 30-35m depth southeast of ChayvoBay where benthic amphipods and cumaceans are the main prey species (Fadeev 2003). Some gray whales have also been seen off western Kamchatka but to date all whales photographed there are also known from the Piltun area (Reeves et al. 2005). Recently whales have also been seen, apparently feeding, in SevernayaBay on the north coast of Sakhalin (IUCN 2006). 

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 16^th century, and by net whalers on the Pacific coast in the 17^th to 19^th 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 20^th century (Henderson 1984), and by Russian steam whalers on the Russian far eastern coast at the end of the 19^th 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 19^th 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)

International Whaling Commission (IWC) regulations protect western gray whales from commercial and aboriginal subsistence whaling; the range states of the Russian Federation, Japan, the Republic of Korea, and China, are members of the IWC (but as noted above, some limited illegal hunting may continue). Oil and gas companies operating off SakhalinIsland have implemented some voluntary measures to reduce their impacts on gray whales, such as speed restrictions on their vessels (Anon. 2006). At present, one oil company is co-operating with the IUCN Western Gray Whale Advisory Panel (WGWAP) although it is not bound by the panel’s recommendations (http://www.iucn.org/themes/marine/sakhalin/).