How to Identify Jack mackerel

To identify Jack mackerel (Trachurus novaezelandiae), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Dorsal surface is typically bluish-green to greenish-grey, fading to silvery on the flanks and belly. A distinct dark spot is often present on the upper operculum (gill cover).

Scale type

cycloid

Mouth position

terminal

Distinctive features

Two widely separated dorsal fins., A series of prominent, keeled scutes (bony plates) along the entire lateral line, becoming larger and more pronounced posteriorly., Large eyes relative to head size., A small, terminal mouth.

Dorsal fin

First dorsal fin with 8 spines; second dorsal fin with 1 spine and 28-33 soft rays. The two fins are distinctly separated.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Long and falcate (sickle-shaped), extending beyond the origin of the second dorsal fin.

Distinctive fins

Anal fin with 2 detached spines followed by 1 spine and 24-29 soft rays. Pelvic fins are small and located beneath the pectoral fins.

Identification Tips

1. 1

   Lateral Line Scutes

   The most definitive feature is the complete lateral line armed with large, keeled scutes from head to tail. These are particularly prominent posteriorly.

2. 2

   Dorsal Fins

   Two clearly separated dorsal fins, with the first being spiny and the second soft-rayed.

3. 3

   Opercular Spot

   Presence of a distinct dark spot on the upper margin of the operculum.

4. 4

   Body Shape

   Streamlined, fusiform body typical of fast-swimming pelagic fish.

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