Jacks are compressed silvery fishes with a pair of dorsal and anal fins, stiff, forked tails and narrow caudal peduncles often protected by a hard ridge of scales known as scutes.

Jacks are compressed silvery fishes with a pair of dorsal and anal fins, stiff, forked tails and narrow caudal peduncles often protected by a hard ridge of scales known as scutes. In most species the first anal fin composed of three short spines is embedded in the skin just behind the anus.

All are carnivores that may form schools or aggregations in a wide range of habitats including estuaries, bays, reefs, and the open sea. Most species are valuable food and sport fishes but large trevallies have been depleted in most areas due to overfishing. Large Carangids feed heavily upon reef fishes and are the most-likely carriers of ciguatoxin, which causes serious illness in mammals if eaten.