Halfmoon Grouper

Epinephelus rivulatus has a body with a standard length which is 2.7 to 3.2 times its depth. The dorsal profile of the head is convex and the intraorbital region is flat. The preopercle is angular with 1 or 2 small spines on the anterior side of the angle while the gill cover is convex. The dorsal fin contains 11 spines and 16-18 soft rays while the anal fin as 3 spines and 8 soft rays. The membrane between the spines is notably notched. The caudal fin is rounded. The colour of the body is reddish to greenish-brown, with each scale on the body having a small white or pale blue spot. Sometimes 4 irregular dark vertical bars are visible, with a 5th bar on the caudal peduncle. The head is dark brown to pale reddish in colour with pale blue vermiculations and white spots on lower jaw and upper lip. The pectoral fin is dusky with a dark red or reddish-brown coloured blotch at its base. The remaining fins are greenish-brown or greyish-brown marked with dark mottling. Its maximum length is 45 cm (18 in), and weight reaches 1.4 kg (3.1 lb)

Epinephelus rivulatus has a wide Indo-West Pacific distribution. It is found from the east African coast from the Gulf of Aden south to South Africa and then east to New Caledonia, north to the Ogasawara Islands of southern Japan, south to Australia. Its range includes northern New Zealand, and it was first recorded from the Kermadec Islands Marine Reserve north of New Zealand in 2015, after researchers examined hundreds of hours of unused documentary film footage. It is d=found in the Indian Ocean islands of the Chagos, Comoros, Madagascar, Mauritius and the Seychelles, it does not occur in Fiji, the Red Sea or Persian Gulf.