‘Opelu are black metallic to blue green and are silvery white along the belly. Their tails are yellow-green and have a small black spot on its operculum, or gill plate. ‘Opelu resembles a mackerel with a long and slender body, similar to that of Akule, but more elongated. It has a sweet, oily flavor similar to mackerel and is great for grilling.
‘Opelu are unique in that they spend their life between two marine habitats, the coral reef and open ocean. They are classified as “coastal pelagic” fish and can grow up to 18 inches. ‘Opelu aggregate when spawning, whereby they spawn pelagic eggs that hatch into pelagic larvae. The traditional Hawaiian kapu system for managing fisheries banned ‘Opelu fishing from March through July during the its spawning period. Juvenile fish swim inshore where they mature and form adult schools by the time they reach sexual maturity at seven to 10 inches, or about 18 months old. They feed predominantly on zooplankton, or small fish, and crustaceans that live in the water column.