Mackerel, common name for any of 48 species of important food fishes having a pointed head, with a large mouth, and a thick, narrow body that tapers just before the bilobed tail. The Atlantic mackerel, which is blue above and silver below, grows to a length of about 50 cm (about 20 in) and a weight of about 1.4 kg (about 3 lb). Numerous fine black lines traverse its back. The mackerel has small finlets behind the dorsal and anal fins. The head has no scales, but the body is covered with numerous small scales. Mackerel swim in huge schools near the surface of the water, feeding on small fish and crustaceans. They spawn in open water during late spring and early summer. The eggs are laid primarily at night and float on the surface. The chub mackerel occurs in the Pacific and Atlantic oceans. Mackerel fishing is a major industry in the northeastern United States, southeastern Canada, Ireland, Great Britain, and Norway.

Scientific classification: Mackerels belong to the family Scombridae of the order Perciformes. The Atlantic mackerel is classified as Scomber scombrus and the chub mackerel as Scomber japonicus.