Green-blue body with a green sheen, white below and streamlined with long pectoral fins. The obvious lateral line is comprised of wide, overlapping scales which expand to form a hard ridge of scutes at the tail base.

Three jack mackerel species are found around New Zealand: Trachurus declivis, T. novaezelandiae, and T. murphyi, all pelagic species belonging to the Carangidae family (trevallies, kingfishes).

Jack mackerel (T. declivis), found only in Australasian waters, especially in the central and northwestern seas.  They are summer spawners, occur in large schools, are fast growing and live for 15 to 25 years. They are caught year-round, mainly off the west coast of North Island.

Horse jack mackerel (T. novaezelandiae) is smaller and slightly deeper-bodied. Green with broad but faint brown bands, white below and grows to 30 to 40 cm. They are distributed from Australasia through southeast Asia to Japan. Often found in harbours and bays, they also live at depths of up to 300 metres. They are caught by purse seiners off the northeast coast.

Slender jack mackerel (T. murphyi) is a slender-bodied large blue-green species. First found in New Zealand in the early 1980s, it extended territory from the eastern Pacific Ocean to the southern. Commonly found around central and southern New Zealand, they are caught by trawler.

Jack mackerel is likely to form part of the Seafood Innovations Ltd research programme, a New Zealand seafood industry initiative looking at ways of adding value to the fisheries resource.