Jack Mackerel

How to identify jack mackerel

A slender, slightly compressed fish with a blue-green to dark blue back and silver sides and belly. A row of enlarged, scute-like scales runs along the lateral line, and a second, accessory lateral line runs along the back. There is a black spot on the upper rear edge of the gill cover, and the eye has a well-developed fatty eyelid.

New Zealand's three jack mackerels look very alike. The length of the accessory lateral line differs between species: in the Pacific jack mackerel (Trachurus murphyi) it ends early, below the 2nd to 5th soft ray of the dorsal fin.

Where it lives in New Zealand

Trachurus novaezelandiae is the common inshore jack mackerel. It schools in water shallower than 150 m and warmer than 13°C, and is uncommon south of 42°S, so it is mainly a North Island fish. T. declivis generally lives deeper, to about 300 m. The Pacific jack mackerel (T. murphyi) reached New Zealand from the South Pacific in the mid-1980s; it lives deeper and further south, centred around 220 m, and has been only sporadic north of Cook Strait since the late 1990s.

How to catch it

Jack mackerel are caught from wharves, especially at night when they gather under lights, and from boats over bait schools. The usual method is a sabiki rig of small flies or bait hooks. Most anglers use them as live or dead bait for kingfish, John Dory and snapper. Commercially, the three species are caught together by purse seine and trawl.

Eating

Oily, dark flesh that lightens when cooked and is high in omega-3. It suits most methods, including baking, barbecuing, poaching, smoking and steaming, and works well marinated or in curries. Jack mackerel is a good source of vitamin D, vitamin B12 and selenium.

Good to know

The three jack mackerels are managed together under the Quota Management System. The Pacific jack mackerel was first recorded in New Zealand waters in 1987, and fish here have been aged to 38 years.

Questions

Is jack mackerel good eating?

It is edible, but most anglers use jack mackerel as bait. The flesh is oily and dark, lightens when cooked and is high in omega-3. It suits baking, barbecuing, poaching, smoking and steaming, and works well marinated or in curries.

What jack mackerel species are in New Zealand?

Three: Trachurus novaezelandiae, T. declivis and the Pacific jack mackerel, T. murphyi. They look very alike. The one most anglers catch in harbours and from wharves is T. novaezelandiae; T. declivis lives deeper, and T. murphyi deeper and further south.

Why are jack mackerel called yellowtail?

Many New Zealand anglers call small jack mackerel 'yellowtail' or 'jack macks'. It's a local name only. Elsewhere, and on most menus, yellowtail means yellowtail kingfish (Seriola lalandi), a much larger fish.