Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Temperate and ice-free boreal zone of northern hemisphere; summer visitor to the productive fringes of the Arctic Ocean (Gaskin 1992; Suydam and George, 1992, Can. Field-Nat. 106:489-492); isolated population in the Black Sea; south to Senegal in the eastern Atlantic. Has disappeared from parts of the Baltic Sea, the southern North Sea, and portions of the central California coast (see Read et al. 1993). See also IUCN (1991) for distribution information.