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 Baltic Sea in the early Holocene (ca. 10,000 years ago) glacier meltwater accumulated between the front of the ice sheet and the southern shores that were free of glacier ice. This accumulation of freshwater constituted a lake known as the Baltic Ice Lake. This lake did not mix with seawater from the west because the ground on the whole depression rose faster than sea level did. Eventually mixing and connection to the ocean did occur when the glacier front retreated to the north beyond Billingen about 11,500 years ago. The Baltic Ice Lake drained then rapidly reaching sea level. From this point