The right whale population in the North Pacific is only a small fraction of what it was prior to 19th century whaling. A preliminary estimate of 26,500-37,000 animals taken (including struck and lost) during the period 1839-1909 was given by Scarff (2001), of which 21,000-30,000 were taken during 1840-49 alone.

Since the start of modern whaling in the North Pacific (1911), 742 right whales are recorded taken (Brownell et al. 2001) of which about 500 were illegal catches by Soviet whaling fleets in the 1960s, that were concealed at the time (Doroshenko 2000).

Brownell et al. (2001) listed a total of 1,965 right whale sighting records in the 20th century. Today, the main remnant population summers in the Sea of Okhotsk between Sakhalin Island and Kamchatka (Russian Federation). Based on sightings of 28 right whales in 2,688 nautical miles of Japanese-Russian cetacean surveys in the Okhotsk Sea in August and September in 1989, 1990 and 1992, Miyashita and Kato (1998) derived a preliminary population estimate of 922 whales (95% CI 404-2,108) using line-transect analysis. Additional Japanese surveys were conducted in 1999, 2000 and 2003 (Miyashita et al. 2000, 2001; Miyashita 2004). These yielded sightings of 23 right whales in 6,966 nautical miles of survey, but the data have not yet been analyzed to provide a population estimate. Given the low precision of the estimate from 1989-92, and the fact that the more recent surveys encountered relatively fewer right whales (3.3 whales per 1,000 miles in 1999-2003 compared with 10.4 whales per 1,000 miles in 1989-92), a new population estimate should be derived, using data from all the surveys to date. Sightings off Japan at other times of year may be whales migrating to or from the Okhotsk Sea.

In the eastern North Pacific, the few animals observed are usually alone and in scattered locations. The only exception is an area of the south-eastern Bering Sea where small groups of right whales have been seen in several successive years (LeDuc et al. 2001, Wade et al. 2006). No quantitative estimates of abundance outside the Okhotsk Sea are available, but the paucity of sightings suggests that right whales in the eastern North Pacific number only in the tens (Brownell et al. 2001). No confirmed sightings of calves were made in this region in the 20th century, and there have been only three thus far in the 21st (Waite et al. 2003, Wade et al. 2006).

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