Jack Mackerel

The Jack Mackerel is a schooling pelagic fish in the genus Trachurus, part of the jack family (Carangidae), found in temperate waters of southern Australia and New Zealand. Also known as the Australian jack mackerel, it forms one of several regionally important Trachurus species worldwide that share a similar slender body and bony lateral scute line. It typically occurs in large, dense schools over the continental shelf, undertaking seasonal migrations linked to water temperature and spawning. Historically supporting substantial commercial fisheries, it remains abundant and widely distributed within its range, playing a key forage role in southern temperate marine food webs with no major conservation concerns.

• Slender, elongate, moderately compressed body
• Dark greenish-blue back with silvery sides and white belly
• Continuous row of bony, keeled scutes along the straight portion of the lateral line
• Two separate dorsal fins, the first short and spiny
• Forked tail with a slightly yellow tint
• Relatively large eye

Typically 25-35 cm, up to 50 cm. Distinguished from the Pacific Jack Mackerel by its geographic range in Australian and New Zealand waters and from true mackerels by its lateral row of bony scutes.

Jack Mackerel inhabit temperate coastal and continental shelf waters around southern Australia and New Zealand, ranging from the surface to depths of around 400 m depending on season and life stage. They favor cooler, productive waters and often form large schools over open shelf habitat rather than near reef structure. Seasonal movements are linked to water temperature, with schools moving inshore to feed and offshore or into deeper water at other times of year. Juveniles may occur closer inshore in bays and coastal waters before joining larger offshore schools as they mature into adults.

Jack Mackerel are strongly schooling fish, often forming large, dense aggregations that move together for feeding, migration, and defense against predators. They feed primarily on zooplankton and small fish, filtering or actively pursuing prey depending on availability, and often perform vertical migrations tied to daylight and plankton density. Spawning occurs in open water during warmer months, producing pelagic eggs that drift with currents until larvae develop. As an abundant schooling species, jack mackerel serve as an important forage fish for larger predators including sharks, tuna, seabirds, and marine mammals, forming a key link in southern temperate ocean food webs.