Clupea Clupea Clupea is genus of planktivorous bony fish belonging to the family Clupeidae, commonly known as herrings. They are found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of "Clupea" are recognized. The main taxa, the Atlantic herring ("Clupea harengus") and the Pacific herring ("Clupea pallasii") may each be divided into subspecies. Herrings are forage fish moving in vast schools, coming in spring to the shores of Europe and America, where they form important commercial fisheries. The species of "Clupea" belong to the larger family Clupeidae (herrings, shads,
Geology of the North Sea The sea level is to higher than present day levels. In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast. The group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Stagnation of deep sea currents in middle Cretaceous times caused anoxic circumstances in the sea water. In many places around the world, dark anoxic shales were formed during