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Jack mackerel

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Trachurus novaezelandiae

Also known as: New Zealand Jack Mackerel, Yellowtail Scad, Koheru (Maori name, though often applied to other species as well)

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Description

Trachurus novaezelandiae, commonly known as the Jack mackerel or New Zealand Jack Mackerel, is a pelagic schooling fish belonging to the Carangidae family. It is characterized by its streamlined body, large eyes, and a distinctive lateral line armed with scutes. This species is an important component of marine ecosystems in its range, serving as both a predator and prey item. It is commercially fished and also targeted by recreational anglers.

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

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.

Dorsal Fins

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

Opercular Spot

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

Body Shape

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

Habitat

Water type
saltwater
Depth
Typically found in coastal and offshore waters from the surface down to about 500 meters (1,640 feet), though most commonly in the upper 200 meters.
Environment
Pelagic, schooling species found over continental shelves and slopes. Inhabits both open ocean and inshore bays and estuaries, often associated with reefs or other structures.
Geographic range
Southwestern Pacific Ocean, primarily around New Zealand and southeastern Australia, including Tasmania. Also reported from Norfolk Island and Lord Howe Island.

Aquarium Information

  • Care level: expert
  • Temperament: semi-aggressive
  • Diet: carnivore
  • Minimum tank size: Not suitable for home aquaria due to size and schooling behavior. Requires very large public aquarium exhibits.
  • Temperature: 15-22°C (59-72°F)
  • pH level: 8.1-8.4
  • Hardness: High (marine salinity)
  • Compatibility: Only with other large, fast-swimming pelagic species in very large exhibits. Not compatible with smaller or slow-moving fish.
  • Special requirements: Requires immense space for schooling, strong filtration, and a constant supply of live or frozen prey. Extremely challenging to maintain in captivity.

Wild Information

  • Conservation status: least concern
  • Seasonality: Available year-round, but abundance and catch rates can vary seasonally, often peaking in warmer months when schools are more accessible.
  • Market price: Variable, generally moderate depending on region and market demand.
  • Commercial importance: high
  • Taste: Mild, slightly oily, with a distinct 'fishy' flavor.
  • Texture: Firm, flaky flesh.
  • Cooking methods: Grilling, Frying, Baking, Smoking, Canning
  • Nutritional value: Good source of protein, Omega-3 fatty acids, and various vitamins and minerals.

Key Facts

Schooling Behaviorbehavior

Jack mackerel are highly schooling fish, forming large, dense aggregations that can extend for kilometers, especially during feeding or spawning.

Ecological Roleinteresting

They play a crucial role in marine food webs as a forage fish, being a significant food source for larger predatory fish, marine mammals, and seabirds.

Dietary Generalistsbehavior

Their diet is broad, consisting mainly of zooplankton (copepods, euphausiids), small crustaceans, and small fish, demonstrating their adaptability as opportunistic predators.

Commercial Importanceinteresting

Globally, various species of Trachurus are among the most heavily fished pelagic species, contributing significantly to global fisheries catches.

Safety Information

Safe
  • Safety level: safe
  • Venomous: No
  • Edibility: edible
  • Handling notes: No specific handling precautions beyond standard fish handling to avoid fin spines and sharp gill plates. Can be slippery when fresh.

Similar Species

Chilean Jack Mackerel

Trachurus murphyi

T. murphyi has a more extensive distribution in the southeastern Pacific and generally has a higher number of scutes on the lateral line (typically 80-100 vs. 60-70 for T. novaezelandiae). Morphometric differences in head length and eye size also exist, but require careful measurement.

Atlantic Horse Mackerel

Trachurus trachurus

Geographically distinct (Atlantic Ocean). While sharing the general 'jack mackerel' body plan and scutes, T. trachurus typically has a less pronounced dark opercular spot and subtle differences in fin ray counts.

Yellowtail Kingfish

Seriola lalandi

While also a carangid, the Yellowtail Kingfish lacks the prominent scutes along the entire lateral line. It has a more robust body, a distinct yellow caudal fin, and a yellow stripe along its flank.

Scientific Classification

Kingdom
Animalia
Phylum
Chordata
Class
Actinopterygii
Order
Carangiformes
Family
Carangidae
Genus
Trachurus
Species
Trachurus novaezelandiae

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