shad

(Alosa sapidissima), a fish of the family Clupeidae (herrings). The largest of the anadromous herrings, the shad is up to 75 cm long and weighs up to 6.4 kg. It is found along the Atlantic coast of North America, from the Gulf of St. Lawrence to Florida. It has been acclimatized in the Pacific Ocean, where it is found from Alaska to San Diego and near Kamchatka. The fish ascend rivers to spawn in the spring. The eggs are deposited in batches. Fecundity is up to 150,000 eggs. The diet consists of plankton (usually the larger forms) and, sometimes, fry. The shad is a valuable commercial fish. In recent years, the catch has decreased considerably because of pollution and the regulation of rivers.