Green Jack

The green jack is moderately large in size, growing to a maximum confirmed length of 55 cm and 2.81 kg in weight. Unconfirmed reports indicate the species may grow much larger; up to 1 m in size, but it is most commonly seen at lengths below 40 cm. The green jack is morphologically similar to a number of other carangids, having an elongated, moderately compressed fusiform body with dorsal and ventral profiles of approximately equal convexity and a slightly pointed snout. The posterior section of the eye is covered by a moderately well developed adipose eyelid, and the posterior extremity of the jaw is vertically under the center of the eye. The dorsal fin is in two parts, the first consisting of 8 spines and the second of 1 spine followed by 22 to 25 soft rays. The anal fin consists of 2 anteriorly detached spines followed by 1 spine and 16 to 21 soft rays. The lobes of both the second dorsal and anal fin are slightly elongated and almost entirely covered in small scales, but are still much shorter than the head length. The lateral line has a pronounced but short anterior arch, with the curved section intersecting the straight section below the spine of the second dorsal fin. The straight section contains 0 to 7 scales followed by 42 to 56 very strong scutes, and 43 to 47 scales overall. The chest is completely scaled. …

The green jack is distributed throughout the coastal waters of the tropical and subtropical waters of the eastern Pacific Ocean. Its range extends along the coast of the Americas from Santa Cruz Island, California, south through Mexico and Central America, and down to Peru. The species also inhabits a number of offshore islands including the Galápagos Islands. The species had been captured on occasion from the Hawaiian Islands since 1923, but was misidentified until William Smith-Vaniz re-examined the specimens in 1981 and identified them as Caranx caballus. Due to the heavy fishing pressures throughout Hawaii and the rarity of captures, it was concluded these few individuals were strays carried by ocean currents from the eastern Pacific, as these were the only known specimens. In 1998 however, the species appeared in fishermen's catches in large numbers, and has ever since, indicating a population has been established in the island chain. The green jack inhabits a variety of continental shelf environments to a depth of at least 100 m, predominantly inshore reef systems, as well as shallow bays, estuaries and lagoons. It leads both a demersal and pelagic lifestyle, forming large schools which can move large distances offshore, allowing them to reach offshore island as well as deep, isolated seamounts.