Golden trevally

The golden trevally, also known as the golden kingfish, banded trevally or king trevally, is a species of large marine fish classified in the jack and horse mackerel family Carangidae, and the only member of the monospecific 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 centimetres (47 in) in length and 15 kilograms (33 lb) 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 1,187 metric tons to 3,475 metric tons 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

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, which in turn is part of the order Carangiformes. The species was scientifically described for the first time by the Swedish naturalist Peter Forsskål in 1775. 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. Consequently, authorities regard Scomber rim as a junior synonym. 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. The specific epithet speciosus is Latin for beautiful. 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'. 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. The species has yet to be included in any molecular phylogeny study of the family. ==Distribution and habitat==

Distribution and habitat

The golden trevally is widely distributed throughout the tropical and subtropical waters of the Indian and Pacific Oceans. Golden trevally are recorded from many Indian Ocean islands including Madagascar, Seychelles and The Maldives. Golden trevally appear to prefer clear water to turbid waters, 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. ==Description==

Description

The golden trevally is a relatively large fish, growing to a maximum recorded size of 120 cm (47 in) in length and 15.0 kg in weight. 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. 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. 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, ==Biology and ecology==

Biology and ecology

, at Georgia Aquarium. feeding, with golden trevally, near Marsa Alam The golden trevally is found either as a solitary individual or in small schools as an adult. This behaviour mimics that of the related pilot fish, Naucrates ductor, with their maneuverability protecting them from their hosts, which in turn provides them with protection from predation from other fish. The golden trevally is a diurnal foraging carnivore which, unlike other carangids, does not normally seek out individual prey items. In the latter case, both sand and any prey items are taken into the mouth and filtered through the gill rakers; sand is expelled, while small organisms are trapped and swallowed. A variety of parasites have been recorded from the species, including copepods, flatworms, and a nematode which inhabits the fish's swimbladder. Reproduction in the golden trevally has been studied in both the Indian and Pacific Oceans. In Hawaii, spawning occurred from late February to early October, with a peak from late April to early September. Five distinct peaks during this time were correlated with the first and third quarters of the moon. Spawning occurred from the early evening into the night. In the Indian Ocean, in the southern Persian Gulf, spawning occurred in April and May, with defined peaks in recruitment of juveniles into the local fishery during September and October. The male:female sex ratio in this population was 1:1.01, close to parity. Growth rates were also studied using otoliths in this population, with an increase in growth rate during the winter (November to April). Von Bertalanffy growth curves were also calculated for the species. ==Relationship to humans==

Relationship to humans

The golden trevally has long been used as a food fish by humans, with archeological sites in the United Arab Emirates yielding the remains of this species dating back to prehistory. The species is still fished for using many traditional methods in the Pacific Islands, where it is netted and speared when it moves to shallower waters. On a larger commercial scale, the species is often caught using gill nets and other artisanal fish-trapping methods. Records in Western Australia indicate commercial fisheries took 3.3 t of golden trevally in 2010, while the catch in Queensland has fluctuated between 0.6 and 5.9 t from 1988-2005. Between 2000 and 2010 the worldwide catch recorded by the FAO varied from 1187 t to 3475 t. with spawning demonstrated in captivity in Japan. Sea Aquarium in an aquarium store The golden trevally is commonly targeted by both anglers and spearfishermen, and is considered to be a gamefish. making it a highly accessible species. Baits commonly employed for golden trevally include prawns and a variety of small fish or cut baits. A variety of lures may be employed when targeting the species, including jigs, poppers, spoons, slices, and minnows, with large minnows trolled around reefs often accounting for larger specimens. Once hooked, golden trevally are known for fast runs and hard fights, especially when reef or other structures are present. , Queensland, Australia Juvenile golden trevally are often used in marine aquaria due to their vivid yellow colour and black banding, ==References==

Source: Wikipedia ↗

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