The blue trevally (Carangoides ferdau), also known as the banded trevally, barred trevally, Ferdau's trevally or Forskaal's jackfish, is a common, widespread species of pelagic marine fish classified in the jack family, Carangidae. The blue trevally is distributed throughout the tropical and subtropical waters of the Indo-Pacific and central Pacific regions, ranging from South Africa in the west to Hawaii in the east. It is a moderately large fish, growing to a recorded maximum length of 70 cm, with the number of rays in the second dorsal fin and the colouring serving as diagnostic features of the species. The species inhabits waters to depths of 60 m, generally inhabiting reefs, beaches, lagoons, and areas with sandy substrates. It is a predatory fish, taking other fish, prawns, crabs, and molluscs, and very little is known of the species' reproductive biology. The blue trevally is of varying importance to fisheries throughout its range, with some regions having high catches of the fish. It is considered to be a gamefish, and is sought after for its excellent eating qualities. Taxonomy and naming The blue trevally is classified within the genus Carangoides, a group of fish commonly known as jacks and trevallies. Carangoides falls into the jack and horse mackerel family Carangidae, the Carangidae are part of the order Carangiformes. The species was first described by the Swedish naturalist Peter Forsskål in 1775 based on a specimen taken from the Red Sea. He named the species Scomber ferdau, thus relating it to the mackerels before the family Carangidae was bought into existence with the creation of Lacépède's genus Caranx. With the advent of carangid taxonomy, the species was transferred first to Caranx and finally to Carangoides, where it has remained to this day. Gilbert Percy Whitley attempted to separate the species into its own genus; Ferdauia, although this classification is not accepted. The species was independently described and named a number of times after its initial naming, with this and confusion with Carangoides orthogrammus in the Indo-Pacific giving rise to a complex history of synonymies. These later names were often transferred between genera before being finally sunk into the name Carangoides ferdau and as such are considered to be invalid junior synonyms. The specific epithet ferdau refers to a person named Ferdau, probably the collector of the holotype specimen. Description The blue trevally is a moderately large fish, growing to a recorded maximum length