Island Trevally

The Island Trevally, or Yellow-spotted Trevally, is a species of jack (family Carangidae) native to the Indo-Pacific region. It belongs to the genus Carangoides, a group of deep-bodied, laterally compressed reef-associated jacks. This species ranges from East Africa and the Red Sea eastward across the Indian Ocean to Hawaii and the central Pacific, including many oceanic islands, which explains its common name. Island Trevally are moderately common on shallow reef flats, lagoons, and drop-offs, where they forage over sand and rubble. They are not currently considered threatened, though like many reef carangids they face localized pressure from habitat degradation. The species is a valued subject for reef fish surveys due to its wide distribution.

Island Trevally have a deep, oval, laterally compressed body typical of Carangoides jacks.

• Color: silvery body with a bluish-green back, fading to white below
• Marks: scattered small yellow to orange spots along the upper flanks, more pronounced in adults
• Head: steep, slightly rounded forehead profile
• Fins: forked yellowish tail; second dorsal and anal fins long-based and low
• Scutes: small, weakly developed scutes along the rear lateral line

It is best distinguished from similar Carangoides by the combination of yellow spotting and a relatively small mouth. Juveniles lack spotting and can be confused with other silvery jacks until spots develop with age.

Island Trevally inhabit tropical marine waters across the Indo-Pacific, from the Red Sea and East Africa to Hawaii, Japan, and the central Pacific islands. They favor clear-water coral reef flats, lagoons, and adjacent sandy or rubble areas, typically at depths of 3-60 meters. Juveniles often shelter in shallow lagoons and seagrass edges, while adults range more widely over reef slopes and drop-offs. The species tolerates a range of reef structures, from fringing reefs to atolls, and is frequently encountered around oceanic islands with limited continental influence, reflecting its common name.

Island Trevally are typically found alone or in small loose groups, occasionally forming larger aggregations over open sand flats near reefs. They are active daytime foragers, cruising over sand and rubble substrates to hunt small fish, shrimp, and crabs, often flushing prey from the substrate. Like other carangids, they are strong, agile swimmers capable of rapid bursts of speed when pursuing prey or evading predators. Spawning is thought to occur in offshore waters, with pelagic eggs and larvae later settling into shallow reef nursery habitats. As mid-level predators, Island Trevally help regulate populations of small reef fish and invertebrates within their range.