The greater amberjack, also known as the allied kingfish, great amberfish, greater yellowtail, jenny lind, purplish amberjack, rock salmon, sailors choice, yellowtail and yellow trevally, and is a species of predatory ray-finned fish in the familyCarangidae, the jacks and pompanos. It is found in temperate, subtropical and tropical seas around the world. It is a popular quarry species for recreational fisheries as well as being an important species in commercial fisheries. It is the largest species in the family Carangidae.
Description
The greater amberjack is a large predatory fish which has a body colouring which varies from brownish to bluish-grey on the dorsal surfaces contrasting with the silevery-white underparts, There is a diagonal sooty stripe which starts at the snout and runs along the centre of the back dorsal fin, another dark stripe runs from the upper jaw, through the eye to in front of the first dorsal fin.. Some fishes may show a light yellow to reddish-brown stripe along the flanks. The fins are dusky in colour. The second dorsal and anal fins have a low anterior lobe. Small juveniles have clear fins and a series of five vertical bands along the body and a sixth band on the caudal peduncle. The shape of the body is elongated and fusiform and it is of moderate depth, laterally compressed and has a covering of small cycloid scales. The largest fish have been measured at in total length but the more frequent length found is, while the largest published weight is.
Distribution
The greater amberjack has an almost circum-global distribution in the subtropical and tropical seas and oceans of the world. In the Indian Ocean it is found along the African coast from South Africa east through the Persian Gulf to Western Australia and southern Japan, reaching the Hawaiian Islands and Micronesia in the Pacific Ocean. It reaches as far south as Tasmania off Australia. In the western Atlantic Ocean this species is found around Bermuda and on the North American coast as far north as Nova Scotia extanding south as far as Brazil, including the Gulf of Mexico and the Caribbean Sea. In the eastern Atlantic Ocean it has been recorded as a vagrant as far north as the British Isles and is found off in the Bay of Biscay south to Morocco and in the Mediterranean Sea. It may occur along the west African coast but here confusion with the similar Seriola carpenteri makes the position unclear.
Habitat and biology
Habitat
The greater amberjack is found as solitary individuals or in small to moderate-sized schools which are epibenthic and pelagic and occur in the vicinity of reefs, deep offshore caves, drop-offs, rocky outcrops and deep seaward reefs. They will sometimes enter coastal bays while the juveniles are infrequently recorded quite far well out to sea where they shelter among floating algae, such as Sargassum and debris. It can also be found over wrecks. Smaller individuals, less than, can be caught in shallow water while the larger fish prefer deeper water, normally between and have been recorded at depths of.
Diet
Greater amberjacks are opportunistic predators when they are adults which prey on benthic and pelagic fishes as well as cephalopods and crustaceans. Common fish prey species include the bigeye scad and sardines. The juvenile fish feed on plankton including the larvae of decapods and other small invertebrates. The juveniles switch to feeding on larger prey such as larger benthic and nektonic organisms when they attain a length of and once they have grown larger than they restrict their prey choice to animals which swim on or over the substrate and when they attain they are mainly piscivorous and it is at this size that they move from open waters to more coastal areas.
Breeding
Seriola dumerli is gonochoric, meaning that the males and females are separate and determined at birth, and there is no sexual dimorphism other than size. The sexes begin to differentiate at around 4-5 months of age when they attain a length of and, In the Mediterranean, they reach sexual maturity at, respectively, 4 and 5 years of age when they attain a length of about in length) in males and females. In western Atlantic populations the males are mature after 3 years and and the females after 4 years of age and attaining. This species has been observed to show pair courtship off Belize where there were schools numbering around 120 individuals and pairing mainly occurred during when there was moon was either full or waning and between the months of February and October. They are sexually dimorphic with the females noticeably larger than the males. Half of the males are sexually mature at fork length for males half of the females are sexually mature on attaining fork length. This is a highly fecund fish and a single female may lay 18 to 59 million eggs in a single spawining season. Off the coast of Florida spawning peaks in April and May and each female is estimated to spawn once every four to five days during the spawning season, lasting around 60 days.I n the Mediterranean spawining takes place in June and July Spawning occurs over such habitats as reefs and shipwrecks, demonstrated by the abundance of juveniles in these habitats in the summer following the spring spawning in the western Atlantic. The eggs are in diameter and after spawning the embryo takes around 40 hours to develop and the newly hatched larvae take 31–36 days to develop into juveniles. They can live to be 17 years of age.
Predators and parasites
Greater amberjack are preyed on by larger fishes and seabirds including the yellowfin tuna, European hake, brown noddy, and sooty tern. Tapeworms are occasionally recorded as infesting this species, these worms being harmless to humans, albeit rather unappetising. The monogeanZeuxapta seriolae has been documented as living as a parasite on the gills of these fish.
Human usage
The greater amberjack is an important food fish and is a commercial quarry species as well as being popular in aquaculture. As a predatory fish it requires protein and lipids sourced from other fish so there are questions over the sustainability of its culture. It is also a popular game species for angling. The meat is used for sushi and sashimi in Japan, while in Florida and Mexico its flesh is marketed fresh and can be fried, broiled, baked, or grilled. They have been used in aquaculture in the Mediterraean since the 1980s. Angling techniques used to catch greater amberjacks include trolling at the surface with various artificial lures and natural baits. They are often incidentally caught by anglers who are fishing the seabed for snappers and groupers.
