Bluefin trevally

Photo: Rickard Zerpe · CC BY

Bluefin trevally are among the most visually striking predators on Hawaiian reefs, with iridescent blue-spotted flanks and aggressive cooperative hunting tactics that see groups herding small fish against the reef. At Niihau, where fishing pressure is absent, individuals reach their maximum size of around 80 cm and form hunting packs that are noticeably bolder than those on fished reefs. They are closely associated with areas of high current and structural complexity, making the island's wall and pinnacle dives prime observation points.