Longfin Trevally

The longfin trevally has a similar body profile to most other jacks, having a deep, strongly compressed body. It is a medium-sized fish, growing to a maximum known length of 57 cm, and at least 3.5 kg in weight. The profile of the head is very steep from the mouth to the nape, especially in adults. There is a weak adipose eyelid covering the eye, which is about equal to or smaller than the snout length. Both jaws are lined with villiform teeth, although larger specimens have small conical teeth in bands. The gill rakers are one of the diagnostic features of the species, having 30 to 37 rakers on the first arch. The dorsal fin is in two parts, the first consisting of 13 spines and the second of 1 spine followed by 19 to 22 soft rays. The second dorsal fin is sexually

dimorphic, with mature males longer than 21 cm having 3 to 12 of the central soft rays extended

The longfin trevally inhabits tropical to subtropical waters of the Indian and west Pacific Oceans. It is distributed from East London, South Africa in the west, north to Madagascar, eastern Africa, India, Thailand, Hong Kong, Taiwan and to Japan in the east. The species is also common in the Red Sea and the Gulf of Oman.

The species inhabits inshore coastal waters rarely venturing offshore, and is pelagic, inhabiting both the upper and lower sections of the water column. Longfin trevally are commonly found on rocky and coral coastlines, often inhabiting reef complexes, with solitary individuals or groups of larger fish patrolling the edges of reefs. They are also found in shallow, sandy bays and lagoons, with juveniles known to enter and use estuaries as nursery areas.

The longfin trevally is a predatory fish, known to take a variety of small fishes, cephalopods including squid, and crustaceans such as crabs and mantis shrimp. The species' long gill rakers also help to filter minute organisms from the seawater, adding to the fish's diet. Longfin trevallies reach sexual maturity at 21 to 22 cm in length. There has been no research into their spawning patterns, although it is known juveniles inhabit shallow bays and occasionally estuaries.