Almaco Jack

Almaco Jack

The almaco jack (Seriola rivoliana), also widely known as the longfin yellowtail, kanpachi, or highfin amberjack, is a robust pelagic fish belonging to the family Carangidae. Distributed across tropical and temperate ocean waters globally, this species is closely related to other amberjacks and yellowtails. Unlike many of its streamlined relatives, the almaco jack possesses a less elongated, deeper, and laterally compressed body shape. Adults typically reach a standard length of around 90 centimetres, though exceptional specimens can grow up to 177 centimetres and weigh as much as 59.9 kilograms (136 pounds). Coloration in almaco jacks is distinctive yet variable. The upper body and lower fins typically exhibit dark blue-green, olive, or dark brown hues, while a faint amber or olive stripe runs along the flank. The underbelly is significantly lighter, often displaying a striking brassy or lavender sheen. A prominent dark nuchal bar extends diagonally from the mouth through the eye towards the dorsal fin. While most fins are dark in mature adults, the ventral surfaces of the pelvic fins remain bright white, creating a subtle contrast when viewed from below. Distinguishing the almaco jack from similar species—such as the greater amberjack, lesser amberjack, and banded rudderfish—relies on fin morphology. The almaco jack features elongated dorsal and anal fins with pronounced, sickle-shaped (falcate) outer edges. Crucially, the longest rays of its dorsal fin are nearly twice as long as the dorsal spines. Unlike many other members of the jack family, the almaco jack completely lacks caudal keels and scutes along its lateral line, which has a moderately long anterior arch. In the wild, almaco jacks are curious pelagic wanderers that frequently form small schools or spawning groups. They are noted for spawning as often as weekly throughout the entire year. Divers often encounter them patrolling deep reefs, steep drop-offs, and marine structures. They exhibit a particularly strong affinity for shipwrecks, visiting submerged wrecks far more frequently than most other jack species. Beyond their ecological presence, almaco jacks hold significant interest for both sport fishers and marine aquaculture. Highly valued for their stamina and dense, rich flesh, they are commercially ranched in deep water off Hawaii and Baja California under the name Kampachi. For scuba divers, an encounter with these sleek, powerful predators offers a memorable display of open-ocean agility and intriguing, bold interaction.