Golden trevally

 

Golden trevally
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Suborder:	Percoidei
Superfamily:	Percoidea
Family:	Carangidae
Genus:	Gnathanodon Bleeker, 1851
Species:	G. speciosus
Binomial name
Gnathanodon speciosus (Forsskål, 1775)
Approximate range of the golden trevally
Synonyms
Scomber speciosus Forsskål, 1775 Caranx speciosus (Forsskål, 1775) Caranx panamensis Gill, 1863 Caranx edentulus Alleyne & Macleay, 1877 Caranx cives De Vis, 1884 Caranx obtusiceps Macleay, 1882 Caranx petaurista Geoffroy St. Hilaire, 1817 Caranx poloosoo Richardson, 1848 Caranx rueppellii Günther (ex Rüppell), 1860

The golden trevally, Gnathanodon speciosus (also known as the golden kingfish, banded trevally and king trevally), is a species of large marine fish classified in the jack and horse mackerel family Carangidae, and the only member of the genus Gnathanodon. The golden trevally is widely distributed throughout the tropical and subtropical waters of the Indian and Pacific Oceans, ranging from South Africa in the west to Central America in the east, extending to Japan in the north and Australia in the south. The species predominantly occupies inshore waters where it inhabits both reef and sandy substrates. The golden trevally is easily distinguished from its relatives by its fleshy, rubbery lips and unique colouration, which ranges from bright yellow with black bars as a juvenile to a golden-silvery colour as an adult. It is known to grow to 120 cm in length and 15 kg in weight. The golden trevally schools as a juvenile, often closely following larger objects including sharks and jellyfish. The species uses its protractile jaws to suck out prey from the sand or reef, and consumes a variety of fish, crustaceans and molluscs. Spawning aggregations gather at night at different times of the year throughout its range. The golden trevally is a considerable constituent of several Middle Eastern fisheries and being of minor importance to many others, with a worldwide annual catch of 1187 t to 3475 t recorded between 2000 and 2010. The golden trevally is a popular gamefish, taken by bait, lure, fly and also spear throughout its range. Several Asian countries currently farm the fish in caged aquaculture. Due to their brilliant colouration, juveniles are popular in marine aquaria.

Taxonomy and phylogeny

A school of subadult golden trevally in Panama

The golden trevally is the only member of the monotypic genus Gnathanodon, which is one of the thirty genera in the jack and horse mackerel family Carangidae, a group of perciform fishes in the suborder Percoidei.^[1]
The species was scientifically described for the first time by the Swedish naturalist Peter Forsskål in 1775.^[2] Forsskål referred the species to the genus Scomber, where many jacks were placed before the recognition of the family Carangidae. The species is initially referred with two epithets; Scomber rim, speciosus in this publication; however the following page names it as Scomber speciosus with 'rim' given as a transcription of the species' Arabic name.^[3] Consequently, authorities regard Scomber rim as a junior synonym.^[4] Forsskål's description was based on an individual from the Red Sea off Jeddah, Saudi Arabia. The holotype has since been lost and a neotype was invalidly designated by Ronald Fricke in 1999.^[5] The specific epithet speciosus is Latin for beautiful.^[6] The species was transferred to Caranx before the Dutch ichthyologist Pieter Bleeker placed it in its own genus Gnathanodon, with this name derived from the Latin for 'toothless jaws'.^[6] In addition to Forsskål's naming, seven other later names have been ascribed to the fish, with all of these now recognised as invalid junior synonyms under ICZN rules.^[4] The species common names generally refer to its appearance with 'golden trevally' (or kingfish), 'banded trevally' and 'king trevally' used. In Hawaii the species is referred to as the 'yellow ulua' or 'papio'.^[7]
A study on the phylogenetic relationships of the Carangidae based primarily on osteology by Soko Gushiken found that Gnathanodon is closely related to and forms a monophyletic group with Caranx.^[8] The species has yet to be included in any molecular phylogeny study of the family.

Description

A juveline golden trevally displaying the prominent dark bands

The golden trevally is a relatively large fish, growing to a maximum recorded size of 120 cm in length^[9] and 15.0 kg in weight.^[10] It is similar to most other trevallies and jacks in having a compressed, oblong body, with the dorsal profile slightly more convex than the ventral profile, particularly anteriorly.^[11] The species' mouth is one of its defining features; the mouth is highly protractile and fleshy, with specimens greater than 90 mm having no teeth on the jaws, vomer or tongue. Smaller individuals have a series of small villiform teeth in both jaws.^[12] The dorsal fin is in two parts, the first with 7 spines, the second with 1 spine and 18 to 20 soft rays. The anal fin has 2 detached spines followed by 1 spine and 15 to 17 soft rays,^[11] while the pelvic fin consists of 1 spine and 19 to 20 soft rays.^[12] The curved part of the lateral line is moderately arched; containing 62 to 73 scales, and approximately equal in length to the straight section containing 15 to 27 scales and 18 to 25 scutes. The breast is completely scaled.^[12][13] There are 27 to 30 gill rakers and 24 vertebrae in total.^[11]
The golden trevally's colour is the species most prominent distinguishing feature, and for which it acquired its common names. Juveniles are a bright golden yellow colour over their entire body and all fins, with 7 to 11 black vertical crossbars all over their body. These bars generally alternate between broad and narrow. The caudal fin lobes have dark tips and there is a prominent black edge to the operculum. As the fish grows, the body becomes more silver to silvery golden and the cross bars fade or disappear, often replaced by dark blotches. The fins remain yellow, often with greenish tinges. The dark edge of the operculum also fades with age.^[13][14]

Distribution and habitat

A golden trevally foraging in the sand

The golden trevally is widely distributed throughout the tropical and subtropical waters of the Indian and Pacific Oceans.^[13] In the Indian Ocean, the species is distributed from South Africa^[6] along the east African coastline, including the Red Sea and Persian Gulf. Its distribution extends east along the Indian and South East Asian coastlines, and south through Indonesia and northern Australia.^[15] Golden trevally are recorded from many Indian Ocean islands including Madagascar, The Seychelles and The Maldives.^[7][9] In the Pacific, the species is spread throughout the South East Asian and Indonesian archipelago north mainland China and Japan and south to eastern Australia and New Zealand.^[7][12] Golden trevally have been recorded from many central Pacific Islands, including Hawaii, with their distribution extending to central America. Here its range extends from the Gulf of California in the north to Colombia in the south.^[14]
The golden trevally predominantly occupies inshore waters of varying substrate, although is know to occur on deeper continental shelf reefs in Australia.^[13] In coastal areas the species inhabits rocky and coral reefs as well as open sand flats where it forages for food.^[9][11] A systematic study in northern Australia indicated it to be one of the only species to be approximately equally distributed in both reef and soft-bottom habitats.^[16] Golden trevally appear to prefer clear water to turbid waters,^[13] and thus is only encountered rarely in low turbidity estuarine environments.^[17] One known exception to this was the capture of several individuals in a shallow mangrove swamp in Baja California which appeared to be foraging for prey.^[

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