Gracila albomarginata (Fowler & Bean, 1930)

Nomenclature

This species, commonly called the masked grouper, has the scientific name Gracila albomarginata (Fowler & Bean, 1930).

Body Shape

The masked grouper has an oblong, relatively compressed body, with a standard length that is 2.6 to 3.3 times its body depth. The dorsal profile of the head is convex, and the area between the eyes is slightly convex.

Operculum Structure

The preopercle is rounded, with fine serrations and a smooth, fleshy lower margin. The gill cover has a central spine located one-third of the way across the gap between the lower and upper spines, and its upper edge is distinctly convex.

Fin Ray Count

The dorsal fin has 9 spines and 14 to 16 soft rays, while the anal fin has 3 spines and 9 to 10 soft rays.

Dorsal Fin Membrane

The membranes between the dorsal fin spines are incised in juvenile fish, but not in adults.

Caudal Fin Shape

The caudal fin is truncate.

Adult Body Coloration

This species has a body colour ranging from greenish to reddish-brown or brownish-grey. It has a large, roughly square-shaped white blotch on its upper flanks, dark diagonal lines on its head, and narrow dark bars along the middle of the flanks.

Caudal Fin Markings

The base of its caudal fin is white, and there is a black spot at the centre of the caudal fin.

Juvenile Coloration

Juveniles are more colourful, with violet bodies and bright red margins on their dorsal, anal, and caudal fins.

Size

The maximum recorded total length of this species is 45 centimetres, or 18 inches.

Broad Distribution Range

Gracila albomarginata is distributed across the Indo-Pacific region, ranging from northern Mozambique north to Kenya, and east to French Polynesia and the northern Great Barrier Reef.

Excluded Distribution Areas

Its known range includes the islands of Réunion, Mauritius, Seychelles, and the Maldives, but it has not been recorded in the Red Sea or the Persian Gulf.

Australian Distribution

In Australia, it occurs at Scott Reef and Rowley Shoals in Western Australia, as well as the Great Barrier Reef in Queensland. It can also be found around Christmas Island and the Cocos (Keeling) Islands.

Habitat

The masked grouper is a reef-associated species, and it normally lives on the outer slopes of coral reefs and in channels near deep water.

Diet

It feeds mainly on fish, which it catches near the seabed.

Social Behavior

This is an uncommon species that is usually solitary, though there are confirmed records of groups of three or four individuals.