Three different species, difficult to tell apart. The average size of fully grown adult jack mackerel is between 30 and 50cm. Jack mackerel are relatively slow growing reaching maturity at 6 to 7 years of age. Big specimens can be as much as 30 years old. Jack mackerel is easily identified by its peculiar armour in the form of overlapping bony plates or scutes which cover its lateral line running down each side. These plates are hard to the touch and proud of the flanks. They are particularly broad near the tail where they form a spiky keel. The tail can be quite yellow in colour on its trailing edge. The lower jaw is slightly longer than the upper. The colour is a darkish green with a faint blue tinge. Below the bony side plates the colour is paler fading to creamy white underneath. Overall the jack mackerel is streamlined in appearance and built for fast swimming.

They are a pelagic species found mostly in mid-water or near the bottom in shore out to at least 300m.

Jack mackerel caught in deeper water were found to be feeding on squid, octopus, sprats, pilchards, flatfish, swimming crabs, krill (whalefeed) and shrimps. Jack mackerel are often found with throat parasites.

The species spawns in summer over the central continental shelf. Females lay as many as 400,000 eggs. An increasingly important commercial species, usually canned but exellent cooked other ways including smoked.
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NZ Marine Fishes: Paul