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. It follows a seasonal migration pattern between summering and wintering areas, although some individuals may remain in certain areas year-round. 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 intermediaand Balaenoptera musculus brevicauda