Bigeye trevally

How do you identify a bigeye trevally?

The bigeye trevally, also called the bigeye jack, is a streamlined jack that averages 60 centimeters and reaches 1.20 meters and 18 kilos. Its very large eye, protected by a well-developed adipose eyelid, gave it its name. Adults are silvery olive to blue-green on the back and silvery white below; at the top of the gill cover they carry a small dark spot, much smaller than the pupil, which the giant trevally lacks, and the dark second dorsal fin ends in a white tip. A row of 27 to 36 strong dark scutes armors the rear flank. Juveniles, silvery yellow to silvery brown, carry five or six dark vertical bands: this is the origin of its Latin name, sexfasciatus, which means six-banded.

How do bigeye trevally live?

The bigeye trevally lives in the tropical and subtropical waters of the Indo-Pacific, from the Red Sea and East Africa to Hawaii, from southern Japan to Australia and New Caledonia, and in the eastern Pacific, from southern Baja California and the Gulf of California to Ecuador and the Galápagos. It frequents reefs from the surface to 146 meters. By day it gathers in large schools, hovering or circling slowly around the reefs; at night it disperses and hunts alone, mostly small fish, but also crustaceans and cephalopods. To spawn, pairs leave the school, and the lower fish turns black. Juveniles grow up in estuaries and sometimes travel far up rivers.

Where and when can you see bigeye trevally?

The bigeye trevally appears on ten of our dive sites, almost always in schools. In Indonesia, its tornadoes block out the light at Castle Rock, in Komodo National Park, especially from April to November, and its schools pass over Batu Bolong; in Raja Ampat, it spins in tornadoes at Blue Magic and Cape Kri, at peak current, especially from October to April. In the Maldives, it is there year-round: schooling above the top of Maaya Thila, and hunting anthias and glassfish against the reef at Kandooma Thila. In Thailand, from October to May, it forms walls above the pinnacle of Richelieu Rock, the show of every dive. In the eastern Pacific, it built the reputation of Cabo Pulmo, in Mexico, with tornadoes of several thousand fish year-round, and Cocos Island, in Costa Rica, has resident schools, on the outer slope of Manuelita and on the nearby pinnacle of Dirty Rock, whose top sits at 18 meters.

Is the bigeye trevally endangered?

The bigeye trevally is listed as Least Concern on the IUCN Red List. It is fished throughout its range, with gillnets, seines and lines, and its flesh has caused ciguatera poisoning. In Cabo Pulmo National Park, on the Gulf of California, its tornadoes of several thousand fish, which wrap around divers on the ridges, have become the park's trademark.