Diamond Trevally, Alectis indica (Rüppell 1830)

Other Names: Diamond Fish, Diamond-fish, High-brow Pennantfish, Indian Mirrorfish, Indian Threadfin, Indian Threadfish, Mirror Fish, Mirror-fish, Plumed Trevally, Threadfin Trevally

A Diamond Trevally, Alectis indica, from Mexico. Source: Gary Bulla / FishBase. License: CC BY Attribution-NonCommercial


Adults have an angular, strongly compressed body, whereas young fish are almost diamond-shaped. Juveniles have extremely long filaments trailing from their dorsal, anal and pelvic fins - and they appear to mimic box jellyfish. The filaments gradually reduce as the fish grows and are absent in adult Diamond Trevally.

Video of juvenile Diamond Trevally, also known as Indian Threadfish.

While juveniles of the closely related Pennantfish, Alectis ciliaris, also have long trailing filaments on the dorsal and anal fins, they lack elongate filaments on the pelvic fins. Adult Pennantfish have a more rounded head profile, versus the more angular head profile of the Diamond Trevally.

Cite this page as:
Dianne J. Bray, Alectis indica in Fishes of Australia, accessed 21 May 2022, https://fishesofaustralia.net.au/home/species/4254

Diamond Trevally, Alectis indica (Rüppell 1830)

More Info


Known in Australia from the Houtman Abrolhos, WA (28º50´S) to Wollongong, NSW (34º26´S); also at Christmas Island in the Indian Ocean. Elsewhere, widespread in the Indo-West Pacific, from the Red Sea and East Africa to French Polynesia, north to southern Japan and south to northern Australia.

Adults are pelagic around reefs, while juveniles are found in a range of habitats, including estuaries and seagrass beds.


Of minor commercial importance in parts of its range, and aquacultured in Southeast Asia.

Similar Species

Similar to the closely related Pennantfish, Alectis ciliaris, that also has long trailing filaments on the dorsal and anal fins. Juvenile Pennantfish, however, lack elongate filaments on the pelvic fins. Adult Pennantfish have a more rounded head profile, versus the more angular head profile of the Diamond Trevally.

Species Citation

Scyris indicus Rüppell 1830, Fische des Rothen Meeres: 128, pl. 33(1). Type locality: Jidda, Saudi Arabia (as Djedda), Red Sea.


Dianne J. Bray

Diamond Trevally, Alectis indica (Rüppell 1830)


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Quick Facts

CAAB Code:37337038

Depth:to 100 m

Fishing:Commercial and sports fish

Habitat:Pelagic, reef associated

Max Size:165 cm TL

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