Longfin Trevally

The Longfin Trevally (Carangoides armatus), also referred to as the Longfin Kingfish, Longfin Cavalla, or Armed Trevally, represents a species within the Carangidae family, commonly known as jacks. This species is prevalent in tropical to subtropical regions of the Indo-Pacific, extending from 🇿🇦 South Africa to 🇯🇵 Japan and typically inhabiting coastal reefs and bays. It can be readily identified by its elongated dorsal and anal fin lobes, filamentous dorsal rays, and characteristic scaleless breast. The Longfin Trevally is a pelagic predator that consumes a range of small fish, cephalopods, and crustaceans, achieving sexual maturity at approximately 21 cm. The largest recorded individual reaches a length of 57 cm and a weight of 3.5 kg. The taxonomic classification of this species is intricate, closely associated with Carangoides ciliarius, which may eventually be identified as synonymous.

Within the genus Carangoides, the Longfin Trevally shares commonalities with other jacks and trevallies and falls under the order Carangiformes. Morphologically, the Longfin Trevally exhibits a body structure typical of jacks—deep and laterally compressed. Characterized as a medium-sized fish, it can grow up to 57 cm. Notably, adults have a steep head profile from the mouth to the nape. A weak adipose eyelid partially covers the eye, and villiform teeth line both jaws, while some larger specimens possess small conical teeth. The species' gill rakers, numbering between 30 and 37 on the first arch, serve as a diagnostic feature. The dorsal fin bifurcates into two segments: the first with 13 spines and the second with a spine followed by 19 to 22 soft rays. The second dorsal fin exhibits sexual dimorphism; in mature males (longer than 21 cm), 3 to 12 of the central soft rays extend into filaments. The anal fin consists of two detached spines anteriorly, followed by a single spine and 16 to 18 soft rays, with pronounced fin lobes. The lateral line is delineated into curved and straight sections, with 57 to 77 and 25 to 43 elements respectively, the latter comprising 11 to 24 weak scutes. Notable for its scaleless breast, this anatomical feature stretches from the pelvic fin origin to the base of the pectoral fin and extends to the gill cover.

The coloration of the Longfin Trevally varies with age, generally presenting a greyish-blue dorsally, transitioning to silvery white ventrally. Juveniles possess a more pronounced silvery-blue with six visible dark crossbars. A distinct black blotch is present on the operculum’s upper margin. Fins exhibit variable coloration: the first dorsal fin ranges from pale grey to black, while the second dorsal and anal fins are hyaline to black. Pectoral fins possess a dusty hyaline hue, pelvics are predominantly black with a white leading edge, and the caudal fin is hyaline with a darkened trailing edge.

Geographically, the Longfin Trevally inhabits the 🇮🇳 Indian and Western 🌊 Pacific Oceans, spanning from 🇿🇦 South Africa’s East London to 🇯🇵 Japan. Common in the 🌊 Red Sea and 🌊 Gulf of Oman, the species resides in inshore coastal environments rather than venturing offshore, and inhabits both depths of the water column. Predominantly found along rocky and coral coastlines, the Longfin Trevally populates reef structures, either alone or in small groups, and frequents sandy bays and lagoons. Juveniles utilize estuaries as nursery areas.

An active predator, the Longfin Trevally preys on various small fish, cephalopods, and crustaceans, with long gill rakers enabling the consumption of small organisms. Sexual maturity is typically reached between 21 and 22 cm, although spawning behaviors remain understudied.

While not a primary target for commercial fisheries due to their rarity, Longfin Trevallies are occasionally captured and sold fresh in local markets. They are esteemed as table fare, particularly in 🇹🇭 Thailand and Cambodia, where they are often steamed or fried. Recreational fishing in 🇿🇦 South Africa yields small quantities, typically via hook and line from boats, or by spearfishing.