The island trevally is a moderately large fish, growing to a maximum recorded length of 75 cm and 6.61 kg in weight.
The species is quite similar to C. ferdau, although the prominent yellow spots serve as a quick identifying feature.
The island trevally has a compressed oblong shaped body with the dorsal profile more convex than the ventral profile and the snout usually being slightly rounded.
The dorsal fin is in two sections, the first consisting of eight spines and the second of one spine and 28 to 31 soft rays, with the lobe of the second dorsal fin being slightly falcate in younger individuals, but is always shorter than the head length.
The anal fin has two detached spines followed by one spine attached to 24 to 26 soft rays, while the pelvic fin has one spine attached to 21 or 22 soft rays.
The lateral line has a very slight anterior arch, with the intersection of the straight and curved sections between the 15th and 19th soft rays of the dorsal fin.
The curved section contains 96 to 106 scales, while the straight section contains 20 to 30 scales and 21 to 28 scutes.
The breast is scaleless ventrally until the origin of pelvic fins, often with a small patch of prepelvic scales.
Laterally, this naked area of the breast is separated from the naked base of the pectoral fins by a moderate band of scales.
The lips are notably fleshy in adults, with both jaws containing narrow bands of villiform teeth which become obsolescent with age.
There are 28 to 32 gill rakers in total and 24 vertebrae.

The island trevally is a pale blue-green above, becoming more silvery below, with adults having several quite large, elliptical, yellow to brassy spots scattered on their bodies close to the midline.
Nine 9 or 10 dark vertical bars may be on the body from the head to the caudal peduncle.
The soft dorsal, anal, and caudal fins are a pale brownish- to brilliant-blue, with all other fins being pale green to hyaline in colour.
The island trevally is a moderately large fish, growing to a maximum recorded length of 75 cm and 6.61 kg in weight. The species is quite similar to C. ferdau, although the prominent yellow spots serve as a quick identifying feature. The island trevally has a compressed oblong shaped body with the dorsal profile more convex than the ventral profile and the snout usually being slightly rounded. The dorsal fin is in two sections, the first consisting of eight spines and the second of one spine and 28 to 31 soft rays, with the lobe of the second dorsal fin being slightly falcate in younger individuals, but is always shorter than the head length. The anal fin has two detached spines followed by one spine attached to 24 to 26 soft rays, while the pelvic fin has one spine attached to 21 or 22 soft rays. The lateral line has a very slight anterior arch, with the intersection of the straight and curved sections between the 15th and 19th soft rays of the dorsal fin. The curved section contains 96 to 106 scales, while the straight section contains 20 to 30 scales and 21 to 28 scutes. The breast is scaleless ventrally until the origin of pelvic fins, often with a small patch of prepelvic scales. Laterally, this naked area of the breast is separated from the naked base of the pectoral fins by a moderate band of scales. The lips are notably fleshy in adults, with both jaws containing narrow bands of villiform teeth which become obsolescent with age. There are 28 to 32 gill rakers in total and 24 vertebrae.
The island trevally is a pale blue-green above, becoming more silvery below, with adults having several quite large, elliptical, yellow to brassy spots scattered on their bodies close to the midline. Nine 9 or 10 dark vertical bars may be on the body from the head to the caudal peduncle. The soft dorsal, anal, and caudal fins are a pale brownish- to brilliant-blue, with all other fins being pale green to hyaline in colour.
Island trevally