shad

Any of several saltwater food fishes of the herring family (Clupeidae) that swim up rivers to spawn. Shad eggs (roe) are a delicacy in the U.S. Adult shad are toothless. The lower jaw of shad in the genus Alosa fits into a notch at the tip of the upper jaw. The American shad (A. sapidissima), an Atlantic fish introduced into the Pacific, is a migratory plankton eater and a good game fish. The Allis (or Allice) shad (A. alosa) of Europe is about 30 in. (75 cm) long and weighs about 8 lbs (3.6 kg). See also whitefish.