Two separate estimates of abundance have been made for waters of the central North Pacific, suggesting that 900,000-1,000,000 Pacific white-sided dolphins may inhabit this oceanic region (Buckland et al. 1993; Miyashita 1993); however, precision was low for both studies, and vessel attraction probably resulted in a substantial overestimation of population size (Buckland et al. 1993). In the eastern North Pacific, the distribution of this species has been documented to vary dramatically with oceanographic conditions (Heise 1997, Forney and Barlow 1998), and abundance estimates along the U.S. West Coast have ranged from about 13,000 to 122,000 (Forney et al 1995, Barlow and Forney, in press). The average abundance in this region during 1996-2001 was estimated to be about 24,000 (Barlow and Forney, in press).

Separate subpopulations have been identified in the southern portions of the species range, off the west coast of North America (Lux et al. 1997) and in Japan (Hayano et al. 2004).

Unknown