shad, fish, Alosa sapidissima, of the family Clupeidae (herring family), found along the Atlantic coast from Newfoundland to Florida and successfully introduced on the Pacific coast. The shad is one of the largest (6 lb/2.7 kg average) of the herrings and has delicious but bony flesh; its roe is valued as a delicacy. Shad ascend rivers to spawn in the spring; water pollution and indiscriminate netting have cut down their numbers. The gizzard shad, Dorosoma (named for its muscular gizzardlike stomach), a swift, silvery fish, 1 ft (30 cm) long, is found along the Atlantic coast from New Jersey to Texas and up the Mississippi to the Great Lakes. Shads are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Clupeiformes, family Clupeidae.
See J. McPhee, The Founding Fish (2002).