[2] The giant trevally is distinguished by its steep head profile, strong tail scutes, and a variety of other more detailed anatomical features.
The giant trevally inhabits a wide range of marine environments, from estuaries, shallow bays, and lagoons as a juvenile to deeper reefs, offshore atolls, and large embayments as an adult.
The species predominantly takes various fish as prey, although crustaceans, cephalopods, and molluscs make up a considerable part of their diets in some regions.
[3] The giant trevally was first scientifically described by Swedish naturalist Peter Forsskål in 1775 based on specimens taken from the Red Sea off both Yemen and Saudi Arabia, with one of these designated to be the holotype.
[17] Individuals with darker dorsal colouration often also display striking silvery striations and markings on the upper part of their bodies, particularly their backs.
[18] The giant trevally is widely distributed throughout the tropical and subtropical waters of the Bay of Bengal and Indian and Pacific Oceans, ranging along the coasts of three continents and many hundreds of smaller islands and archipelagos.
Its range extends eastwards along the Asian coastline, including Pakistan, India and into Southeast Asia, the Indonesian Archipelago and northern Australia.
[11][14] The giant trevally inhabits a very wide range of offshore and inshore marine environments, with the species also known to tolerate the low salinity waters of estuaries and rivers.
[21] The species is most common in shallow coastal waters in a number of environments, including coral and rocky reefs and shorefaces, lagoons, embayments, tidal flats and channels.
[27] Juvenile to subadult giant trevally are known to enter and inhabit estuaries, the upper reaches of rivers and coastal lakes in several locations, including South Africa,[28] Solomon Islands,[29] Philippines,[30] India,[31] Taiwan,[32] Thailand,[33] northern Australia,[34] and Hawaii.
[26] In the Philippines, a population of giant trevally inhabit (and were once common in) the landlocked fresh waters of the formerly saltwater Taal Lake, and are referred to as maliputo to distinguish them from the marine variant (locally named talakitok).
[41] The giant trevally is a powerful predatory fish, from the estuaries it inhabits as a juvenile to the outer reefs and atolls it patrols as an adult.
In all but one study (which was of juveniles), the giant trevally dominantly takes other fishes, with various crustaceans, cephalopods and occasionally molluscs making the remainder of the diet.
[11][44] In Hawaii, the species has a predominantly fish-based diet consisting of Scaridae and Labridae, with crustaceans, including lobsters, and cephalopods (squid and octopus) making up the remaining portion.
[21] Off Africa, the diet is similar, consisting mostly of fish including eels, with minor squid, octopus, mantis shrimp, lobsters and other crustaceans.
[26] Estuarine fish in both Hawaii and Australia have mostly fish-based diets, with crustaceans such as prawns and amphipods also of importance, and they are known to take more novel prey, such as spiders and insects, in these habitats.
[35] Giant trevally also feed on fledgling sooty terns on Farquhar Atoll snatching them from the water surface and even jumping acrobatically to catch them in the air as seen on the BBC documentary Blue Planet II, episode 1.
[citation needed] Studies in controlled environments on the giant trevally's feeding strategies have found hunting in schools increases their capture efficiency, but is not necessary for an individual's survival.
[49] A similar strategy has been employed by fish in the presence of large reef sharks, as they use the larger animal as a tool to ambush prey.
[46] The opportunistic nature of giant trevally has also been made evident by studies on the mortality rate of undersized or egg-bearing lobsters released from traps at the water's surface of the Hawaiian Islands.
[21] Lunar cycles are also known to control the spawning events, with large schools forming in certain locations at specific phases of the moon in Hawaii and the Solomon Islands.
[51] The giant trevally's early larval stages and their behaviour have been extensively described, with all fins having formed by at least 8 mm in length, with larvae and subjuveniles being silver with six dark vertical bars.
[52] The giant trevally has been used by humans since prehistoric times, with the oldest known records of the capture of this species by Hawaiians, whose culture held the fish in high regard.
The ulua, as the fish is known to Hawaiians, was likened to a fine man and strong warrior, which was the cause of a ban on women eating the species in antiquity.
Despite this, intrusions of giant trevally into modern-day fishponds used by Hawaiians for rearing fish are unwelcome; being a predator, it eats more than it is worth at market.
[55] FAO statistics of the Asian region record catches between 4,000 and 10,000 tonnes between 1997 and 2007,[56] although this excludes most fisheries which are not monitored or do not discriminate between trevally species.
The giant trevally is commercially caught by a number of methods, including hook and line, handlines, gill nets and other types of artisanal traps.
The species is commonly taken on bibbed plugs, minnows, spoons, jigs and poppers, stickbaits, soft plastic lures and saltwater flies.
[58] In recent years, the development of both jigging and surface-popping techniques has seen the giant trevally become an extremely popular candidate for catch and release fishing,[10] with many charter operators based around this concept.
[59] Since 1990, giant trevally taken from the main Hawaiian islands have been blocked from sale by auction internationally due to concerns over liability from ciguatera poisoning.