Horse-eye jack

Photo: Kevin Bryant · CC BY-NC-SA

Horse-eye jacks are mid-level predators that hunt in coordinated schools, using their combined mass to herd smaller fish against the reef or into tight bait balls before striking. Their large eyes — proportionally bigger than most carangids — indicate adaptation for hunting in low-light conditions at depth. Schools at Nag's Head often number in the hundreds, circling divers in tight formation in behaviour that may be investigative or related to using diver bubbles to disorient prey. A healthy jack population is a reliable indicator of good water quality and intact food chains supporting sufficient baitfish.