In the North Atlantic Ocean (including the Black and Azov seas), fourteen population units have been proposed (Donovan and Bjørge 1995), and in the North Pacific, several population units have been identified based on genetic studies (Chivers et al. 2002).

There are no synoptic surveys covering the entire range within ocean basins, but abundance has been estimated for selected portions of the range. Abundance estimates have been summarized by Read 1999 (but see updates in Angliss and Outlaw 2005, Carretta et al. 2006, Waring et al. 2006). About 73,000 animals have been estimated to occur along the west coast of the USA (including 1,656 [CV=0.39] in the Morro Bay population, 1,613 [CV=0.42] in the Monterey Bay population, 8,521 [CV=0.38] from San Francisco to the Russian River, 17,763 [CV=0.39] in northern California and southern Oregon, 39,586 [CV=0.38] in Oregon and Washington, and 3,509 [CV=0.40] in Washington inland waters). In Alaska abundance is estimated at about 89,000 (including 10,947 [CV=0.24] in southeast Alaska, 30,506 [CV=0.21] in the Gulf of Alaska, and 47,356 [CV=0.22] in the Bering Sea) (see summary in Angliss and Outlaw 2005). In the western Atlantic, there are an estimated 75,438 [CV=0.42] in the Gulf of Maine/Upper Bay of Fundy to the entrance of the Gulf of St. Lawrence, and 27,000 for the Gulf of St. Lawrence (Waring et al. 2007). Abundance has been estimated at 27,000 in Iceland (Stenson 2003) and 11,000 [CV=0.44] off North Norway - Barents Sea (Bjørge and Øien 1995). In the waters of the European Atlantic, abundance in 2005 was estimated at 385,600 [CV=0.20] (P.S. Hammond pers. comm.), of which about 335,000 [CV=0.21] were estimated in the North Sea and adjacent waters, where abundance was estimated at 341,000 [CV=0.14] in 1994 (Hammond et al. 2002). The abundance in the Baltic Sea is estimated at 599 (CV = 0.57) (Hiby and Lovell 1996). Line transect surveys have been conducted recently (since 2001) to estimate harbour porpoise abundance in different portions of the Black Sea. These suggest that total population size in the region may be at least several thousand and perhaps as much as 10,000-12,000 (Reeves and Notarbartolo di Sciara 2006).

Taken together, these numbers indicate that the global abundance of the harbour porpoise is at least about 700,000 individuals.

There is evidence of decline in abundance in some areas, e.g. in the Black Sea (Reeves and Notarbartolo di Sciara 2006), in the Baltic Sea (see account for that subpopulation), and in inland waterways of Washington State, USA (Osmek et al. 1996).

Unknown