Average length T.declivis 35-50cm; 30-40cm for T.novaezelandiae.Average weight 850gm.
Both species, which are superficially similar, occur around New Zealand and southern Australia; T.novaezelandiae also in south east Asia and Japan.
Blue, or green with faint brown bands above, silvery white below; small scales, and a row of rough scutes along the body.
Both jack mackerels are widespread and common on the bottom, in midwater and occasionally at the surface, around most of New Zealand, especially the west coast of North Island (T.declivis) and the Bay of Plenty (T.novaezelandiae) to depths of 300m; T.declivis is the more abundant species and is caught by trawl. T.novaezelandiae is caught by purse seine. Available all year round. A large resource of each species with estimated annual yield of perhaps 15,000 to 20,000 tonnes for T.declivis and 10,000 to 20,000 for T.novaezelandiae.
The related koheru has similar general appearance but differs in having a rounder body section and only a small number of scutes near the tail. Koheru is common in some localities around the north of North Island but is not abundant and is only a small resource.
