About Mycteroperca olfax (Jenyns, 1840)
Mycteroperca olfax, commonly called the sailfin grouper, has an elongated, robust, laterally compressed body. Its body depth is equal at the origin of both the dorsal fin and the anal fin, and its standard length measures 2.9 to 3.1 times its body depth. The preopercle is angular, with a serrated lobe at its angle. The dorsal fin has 11 spines and 16 to 17 soft rays, while the anal fin has 3 spines and 11 soft rays. The membranes between the dorsal fin spines are not deeply notched, and the soft-rayed portion of the dorsal fin has a rounded shape. Adult sailfin groupers have an emarginate caudal fin, and juveniles have a truncate caudal fin. The head and body are typically pale grey-brown, covered in numerous closely spaced brown spots, and sometimes feature 10 to 12 thin, potentially broken dark bars across the upper body. The fin margins are dark and marked with narrow white borders. Rarely, individual sailfin groupers may be entirely bright yellow. This species reaches a maximum total length of 120 centimetres (47 in). The sailfin grouper is native to the eastern Pacific Ocean, where it is found in waters around Ecuador’s Galapagos Islands, Costa Rica’s Cocos Island, and Colombia’s Malpelo Island. Sporadic vagrant individuals have been recorded along the mainland coast between Costa Rica and Peru. Adult sailfin groupers live along rock walls, rocky reef drop-offs, underwater lava ridges, and other vertical rock formations. Juveniles are found in shallow sandy lagoons, seagrass beds, mangrove lagoons, shallow lava reefs, and even inland lava ponds. Adults are piscivorous, and the main prey of large adult sailfin groupers is the Pacific creolefish (Paranthias colonus). Female sailfin groupers reach sexual maturity at 4 years of age, when they reach a total length of around 47.5 centimetres (18.7 in). They transition to male at around 12 years of age, when they reach a total length of 83.7 centimetres (33.0 in). The species’ skewed sex ratio and lack of small males suggest it is a monandric protogynous hermaphrodite, though this has not been confirmed through histological analysis. Spawning occurs from October to April, peaking in October and December, and spawning aggregations have been observed. Outside of the spawning season, males and females appear to be ecologically separated, with males occurring further offshore than females.
