Latin name

Alectis indica

Other name

Indian threadfin, diamond trevally, mirror fish or plumed trevally.

Identification

Juveniles have a rounded posture with extremely long filamentous rays of unpaired fins. The body is rhomboid, tall, strongly compressed at the sides. It is more or less completely covered with very fine scales which are embedded in the skin. Preorbital bone almost 1.5-2 times the diameter of the eye. Shields on straight part of lateral line somewhat enlarged, bony, barbed. Mouth with bands of small teeth on jaws, scopa, palate and tongue. Gill stamens moderately large; number 8-10 + 21-25. Pyloric appendages 260.

Features of fish fins

Caudal peduncle narrow, caudal fin broadly forked. First dorsal fin poorly developed, spiny rays rudimentary and short, disappearing with age. The soft dorsal and anal fins are similar; the first 5-6 rays of each fin are elongated and filamentous in juveniles, becoming shorter with age. The pelvic fins are elongated in juveniles and short in adults. The pectoral fins are crescent-shaped.

Fish colouring

The colouration of the Indian threadfish is silvery with a blue-green tinge on top. Juveniles have five to seven broad dark stripes.

Distribution

Widespread throughout the Indo-Pacific region. In the Pacific, they are found as far north as Taiwan and almost as far south as Shanghai.

Habitat

It lives in coastal waters at depths of up to 100 metres.

Size

The maximum size of this species is 165 cm, with a maximum weight of 25 kg. The common size is around 100 cm.

Behavior

They live in underwater caverns. Their slender and manoeuvrable form allows them to navigate tunnels. Indian threadfish make their homes in thin cracks in the surrounding rock, crevices that other species find difficult to reach.

Food and feeding habits

A predator, it feeds on fish, small squid, jellyfish and crustaceans.

Reproduction

The reproduction of this species is largely unknown.

Fishing

This species is of minor commercial importance. 

Relationship with a person

The Indian threadfish is a popular sport fishing trophy.