Herring, an important food fish found in abundance in the North Atlantic, North Pacific, and other northern seas. The herring is related to the shad and menhaden. The average adult herring is about one foot (30 cm) long. It is bluish above, with silvery sides. The deep body has a single dorsal (back) fin. The scales are large and loose. Herring feed chiefly on small plant and animal organisms called plankton. Herring swim near the surface in vast shoals consisting of 3,000,000 or more individuals.

Each female lays about 30,000 eggs in shallow water. The young usually hatch in about 22 days. Herring can live for 20 years, but most are caught in their first few years by fishermen or are eaten by whales, seals, large fish, gulls, or cormorants.

Adult herring are prepared for eating by salting (pickled herring) or by salting, then drying or smoking (kippered herring, or kippers). Small herring are among the several varieties of fish canned as sardines. Many are processed for oil, fertilizer, bait, and pearl essence (a translucent substance used to make artificial pearls and lacquer).

The Atlantic herring is Clupea harengus; Pacific, C. pallasii. Herring belong to the herring family, Clupeidae.