The blue whale is found in every ocean except the Arctic, with a range that extends from the periphery of drift-ice in polar seas to the tropics, although it is absent from some seas such as the Mediterranean, Okhotsk and Bering (1). It follows a seasonal migration pattern between summering and wintering areas, although some individuals may remain in certain areas year-round (11). The species’ range can be loosely organised into three main populations: one in the North Atlantic (Balaenoptera musculus musculus), one in the North Pacific (Balaenoptera musculus musculus), and another in the southern Hemisphere (Balaenoptera musculus intermedia and Balaenoptera musculus brevicauda) (1).
In the Antarctic region, which formerly supported the largest blue whale population, the blue whale occurs from the Antarctic Polar Front up to and into the ice in the summer, and is thought to migrate equator-wards before winter. The pygmy blue whale is most abundant on the Madagascar plateau in the southern Indian Ocean, and off south and western Australia (1).
In the North Atlantic the summer distribution of the blue whale extends from the Scotian Shelf to the Davis Strait in Canada, eastwards to Iceland, the Denmark Strait and Svalbard, and north to the ice edge. The winter distribution of the blue whale in the North Atlantic is poorly known, but it is thought that in the past the blue whale was widely distributed in the southern half of the North Atlantic in the winter (1).
The blue whale occurs in the eastern Pacific from southern Chile to Costa Rica, where it is present year-round. In the North Pacific, it is found from the coast of Oregon to the Kurile Islands and north to the Aleutian Islands. In the past the blue whale was regularly caught off southern Japan and the Korean peninsula, but it has not been seen there in recent years (1).
See this species on Google Earth.