Bigeye Trevally

The Bigeye Trevally, scientifically known as Caranx sexfasciatus and often called the bigeye jack or dusky jack, is a notable marine fish from the family Carangidae. This species is predominantly found in the warm tropical waters of the 🇮🇳 Indian and 🌊 Pacific Oceans. Its range spans from the western coast of 🇿🇦 South Africa and 🇲🇬 Madagascar across to Southeast Asia, north to 🇯🇵 Japan, and south to 🇦🇺 Australia. In the Pacific, it is also present from 🇺🇸 California and 🇲🇽 Mexico's southwestern coast all the way to 🇪🇨 Ecuador and the Galapagos Islands.

The fish is recognized for its distinctive appearance, including a dark second dorsal fin with a white-tipped lobe and a small dark spot on its gill cover. Adult Bigeye Trevallies exhibit silvery olive to blue-green coloring on their upper body, shifting to silvery olive or whitish below. Juveniles, in contrast, are marked by silvery yellow to brown hues with noticeable vertical bands.

A member of the Caranx genus, the Bigeye Trevally has a compressed, oblong body with a more convex dorsal profile than its ventral side, a pointed snout, and a strong two-part dorsal fin. It can reach a maximum length of 120 cm (about 3.9 feet) and a weight of up to 18 kg (approximately 40 lbs), although common lengths are around 60 cm (about 2 feet).

The species is versatile in habitat preference, dwelling in both coastal and offshore waters linked to coral and rocky reefs, down to depths of 146 meters (about 479 feet). It also enters estuaries and can be found in rivers during its juvenile stage. The adults form large schools during the day and become more solitary and active at night, feeding primarily on fish and supplementing with squids and crustaceans.

The Bigeye Trevally is of moderate economic importance, particularly to artisanal fisheries, due to its commercial and recreational value. It is typically caught using methods such as hook-and-line, gill nets, and purse seines. While it is considered good for consumption—available fresh, dried, salted, or frozen—there have been instances of Ciguatera fish poisoning reported, which is important for consumer awareness.

Sexual maturity is reached when individuals are about 42 cm (16.5 inches) in length, with spawning occurring in large groups from July to March. Not only does this species contribute economically, but it also plays a significant ecological role as a predator of smaller fish and invertebrates, while also being prey for larger marine animals. Its adaptability to various environments and prominent schooling behavior make the Bigeye Trevally a fascinating subject of study in marine biology.