Diamond Trevally

Interesting Info

• The Diamond Trevally (Alectis indica) looks like it swam straight out of a fairytale — its body is paper-thin, mirror-bright, and shaped like a gleaming diamond slicing through the sea.
• When sunlight hits their scales, they flash silver, gold, and blue all at once, earning them nicknames like “mirrorfish” and “diamond kingfish.”
• Juveniles are especially eye-catching — they have long trailing dorsal and anal fin filaments that wave like ribbons as they drift along, mimicking jellyfish tentacles to confuse predators.
• They are found throughout the Indo-Pacific — from South Africa and the Red Sea across to Japan, northern Australia, and as far east as Fiji.
• In Australia, they occur mainly from Shark Bay and the Pilbara region of Western Australia, across the tropical north to Queensland and northern New South Wales.
• Diamond Trevallies prefer warm, clear coastal waters and offshore reefs down to about 100 m (330 ft). Juveniles are often seen near beaches or estuaries, sometimes sheltering under jellyfish or drifting debris for protection.
• They feed on small fish, squid, and crustaceans — often gliding slowly before striking with sudden bursts of speed.
• As they grow, the long fin streamers of juveniles shorten, and the body becomes taller and more diamond-shaped, giving adults their signature look.
• Spawning takes place offshore, usually during warmer months. Eggs and larvae drift freely in open water before the young settle in shallow nursery areas.
• They can live for over 15 years, reaching maturity at around 50 cm (1.6 ft). Their slow growth and long lifespan make them more vulnerable to heavy fishing pressure in some areas.
• Divers often describe them as one of the most graceful fish on the reef — slow, gliding, and shimmering like living light.