Sea lamprey found in the northern and western Atlantic Ocean along the shores of Europe and North America, in the western Mediterranean Sea, the Black Sea, and in the shores of the Great Lakes. They have been found at depths to 4000 m and tolerate temperatures between 1.0 and 20 °C. The largest European populations of sea lampreys are located throughout the south-western areas of Europe (north-central Portugal, north-northwest of Spain, and west–south-west of France). These countries also support the main fisheries of the species. Sea lampreys are anadromous. From their lake or sea habitats, they migrate up rivers to spawn (followed
North Sea sea grass used to coat huge tracts of ocean floor, but have been damaged by trawling and dredging have diminished its habitat and prevented its return. Invasive Japanese seaweed has spread along the shores of the sea clogging harbours and inlets and has become a nuisance. Due to the heavy human populations and high level of industrialization along its shores, the wildlife of the North Sea has suffered from pollution, overhunting, and overfishing. Flamingos and pelicans were once found along the southern shores of the North Sea, but became extinct over the 2nd millennium. Walruses frequented the Orkney Islands through