JashThe blackjack (Caranx lugubris), also known as the black trevally and other names, is a large species of fish classified in the jack family, Carangidae. The species inhabits oceanic, offshore waters of the tropical zones of the Pacific, Atlantic, and Indian Oceans. The species is particularly prevalent around offshore islands such as the Caribbean islands in the Atlantic, Hawaii and French Polynesia in the Pacific, and Seychelles and Maldives in the Indian Ocean. The species is generally solitary and highly migratory.
Black jack can reach a maximum known length of 88 centimeters (35 inches) and a weight of 16 kilograms (35 pounds). The species exhibits sexual dimorphism in that the females are larger than males. They both display the same silvery-blue to brassy coloration and have a characteristic dark opercular spot and stripe. The species has a deep, compressed body shape and the posterior portion of the soft dorsal fin is distinctively curved. Black jack is predatory fish that generally feed on mollusks, crustaceans, and smaller fishes, particularly lanternfishes.
The blackjack is similar to some other large jacks and trevallies of the genus Caranx; it differs from the crevalle jack (Caranx hippos) primarily in the morphology of the head. The blackjack is known to grow to a length of 100 centimeters (cm) and 15 kilograms (kg), however, it is believed that larger individuals are uncommon. The species feeds on pelagic fishes, squids, cephalopods, crustaceans, and other benthic organisms.
The blackjack is of moderate importance to fisheries throughout its range, and the meat is considered very tasty. The species is taken both by line and net, however, it rarely forms large schools like some other carangid fishes such as jacks. The species attains sexual maturity between 28 and 33 cm in length for males and 26 cm in females, with spawning peaks varying by region. It is believed that spawning occurs between March and October in the Caribbean, whereas off of French Polynesia and Hawaii peaks occur during May and June and February to April respectively. The larvae of the species are known to inhabit surface waters, unlike most of its relatives.
The specific epithet for the fish was originally described as stellatus in 1758 by Peter Forsskål, however, this name was later found to have been already assigned to a coelenterate and thus invalid under the International Code of Zoological Nomenclature. The species was reassigned to the genus Caranx from Plotus Cuvier in 1833 by Henri Émile Sauvage.