Genetic studies and differential recovery patterns (LeDuc et al. 2002) suggest that the small western North Pacific subpopulation is isolated from the larger eastern subpopulation. The former is listed as Critically Endangered (see separate account).

Both eastern and western gray whales were hunted in prehistoric times, but aboriginal catches declined to relatively low levels by the early 20th century due to depletion of the stocks by commercial whaling and the general decline of the traditional aboriginal economies (Mitchell and Reeves 1990).

Eastern gray whales were rapidly depleted by commercial whalers operating in the breeding lagoons when they were discovered in the mid-19th century, estimated peak catches (averaging over 480 whales per year) occurring between 1855 and 1865. Lagoon whaling ended by about 1875, apparently due to exhaustion of the lagoon populations, but shore-based whaling in California continued at a lower level until the late 19th century (Henderson 1984; IWC 1993). In the 20th century, there were some pelagic catches off California and Mexico by Norwegian and American vessels in the 1920s and 1930s, and in the 1930s and 1940s by a Soviet pelagic fleet in the Bering and Chuckchi Seas (Donahue and Brownell 2001; Brownell and Swartz 2006). A further 320 gray whales were taken under scientific permit in the 1960s (Rice and Wolman 1971), and 138 illegal Soviet catches occurred in the 1960s (Doroshenko 2000). Substantial “aboriginal subsistence” whaling in the Bering and Chukchi seas off Chukotka (Russian Federation) resumed in 1948 and has continued into the present, apart from an interruption in the early 1990s during the collapse of the USSR. Catches during the last 50 years (1956-2005) have averaged around 150 per year. Very small numbers have also been taken by aboriginal whalers in Alaska (US), and, in recent years, by the Makah tribe in Washington State, (US) (Donahue and Brownell 2001; IWC 2005).

Despite the continuing catches, the eastern subpopulation has recovered strongly from past over-exploitation, increasing by 2.5% per annum during 1967-96 (Buckland and Breiwick 2002). The subpopulation seems to have peaked around 1997/98 when a census on the southward migration indicated a population of 24,000-36,000; it may have declined since the most recent estimate is 15,000-22,000 for 2001/02 (Rugh et al. 2005). However, there are a number of unresolved possible explanations for the downturn, inter alia related to an ‘overshoot’ of carrying capacity (Moore et al. 2001) and/or unusual environmental conditions around the turn of the millennium resulting in poor calf production, high stranding rates and relatively high numbers of emaciated animals (e.g. LeBouef et al. 2000, IWC 2003, Rugh et al. 2005). Perryman et al. (2002) showed that calf production was related to the proportion of feeding habitat free of sea ice in the preceding summer. Since 2002, calf production has recovered, and mortality and the occurrence of emaciated whales have declined (IWC 2004). The population has probably reached a size where it exceeds the carrying capacity of the environment in years where food availability is below average and is likely to fluctuate around some environmentally determined average level (IWC 2003).

The western Pacific subpopulation remains at a small fraction of past levels and is estimated to number about 100 individuals, of which 20-30 are mature females (Reeves et al. 2005), based on analysis of photo-identification data (see separate listing for the western Pacific subpopulation for more information).

Stable