The black jack, Caranx lugubris, also known as the black trevally, black kingfish, coal fish and black ulua, is a species of large marine fish in the jack family Carangidae. The species has a circumtropical distribution, found in 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 the Seychelles and Maldives in the Indian Ocean. Black jack are rare in shallow waters, preferring deep reefs, ledges and seamounts in clear waters. The species is easily distinguished by its black to grey fins and jet black scutes, with the head having a steep profile near the snout. The largest recorded length is 1 m and weight of 17.9 kg. The black jack lives either individually or in small schools, and is known to school with other species. It is a predatory fish, taking a variety of fish, crustaceans and molluscs as prey. Black jack are of high importance to many island fisheries, but are rarely encountered in most continental fisheries. The species has a reputation as a gamefish, and is variably considered a terrible or excellent food fish, although several cases of ciguatera poisoning (a gastrointestinal and neurological illness caused by toxins which are produced by dinoflagellates and which can bioaccumulate in some reef fish at the top of the food chain) have been attributed to the species.

(Luna 2010; Pottier et al. 2002; Wikipedia 2011; Wikipedia 2012