Blue mackerel - Scomber australasicus

Characteristic features:

2 small keels on either side of caudal peduncle

Teeth present on roof of mouth

Adipose eyelids cover front and rear of eye

10–13 dorsal fin spines

Second dorsal fin anterior of anal fin

First anal-fin spine stiff and strong

Colour:

Blueish green above with many oblique wavy dark lines, pearl white below with wavy, broken lines giving faintly speckled appearance.

Size:

Up to 45 cm TL, and up to 1.4 kg in weight.

Distribution:

Indo-Pacific in subtropical waters.

Habitat:

Epipelagic, found at depths between 87–200 m.

Biology:

Feeds primarily on plankton by filtering small crustaceans such as copepods form the water column. Adults also feed on small fish and squid. Forms large schools with similarly sized fishes such as other mackerel and sardine. This species displays variable life history parameters depending on location. In Australia, age of first maturity is estimated at 2 years,¹ and length where 50% of individuals become mature is estimated at 28.6 and 23.6 cm FL for females and males respectively.² In Japan, blue mackerel larger than 31.0 cm FL were considered mature.3 This species is larger and longer lived in New Zealand, maturing at 3 years, corresponding to 28 cm FL,⁴ and has an estimated maximum age of 24 years.⁵ Blue mackerel are batch spawners, with the spawning period varying with location. In waters off southern Australia, spawning occurs between November and April, with a spawning frequency ranging between 2–11 days. Females can produce ~70,000 eggs per batch.²