How to Identify Semicircle Angelfish

To identify Semicircle Angelfish (Pomacanthus semicirculatus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Juveniles: Dark blue body with 5-7 concentric white or light blue semicircular bands, with the outermost band extending onto the caudal fin. Adults: Greenish-brown to yellowish body, often with a purplish sheen, covered in numerous small blue spots. The caudal fin is bright yellow. A prominent dark spot is often present on the posterior dorsal fin. The operculum has a dark blue margin.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Dramatic ontogenetic color change from juvenile to adult., Juvenile pattern of concentric white/blue semicircles., Adult pattern of blue spots on a greenish-brown/yellow body., Bright yellow caudal fin in adults., Preopercular spine present, characteristic of angelfish.

Dorsal fin

Dorsal fin with 13-14 spines and 18-23 soft rays. The soft-rayed portion is elongated and pointed in adults.

Tail fin

Caudal fin is rounded to slightly emarginate, bright yellow in adults.

Pectoral fin

Pectoral fins are relatively large and rounded.

Distinctive fins

Anal fin with 3 spines and 18-20 soft rays, also elongated and pointed in adults. Pelvic fins are thoracic.

Identification Tips

1. 1

   Juvenile coloration

   The most distinctive feature of juveniles is the dark blue body with concentric white or light blue semicircular bands. This pattern is unique among angelfish.

2. 2

   Adult coloration

   Adults are identified by their greenish-brown to yellowish body covered in numerous small blue spots, and a bright yellow caudal fin. The dark spot on the posterior dorsal fin is also a good indicator.

3. 3

   Size

   This is a large angelfish, reaching up to 38 cm (15 inches) in total length. Its size can help distinguish it from smaller angelfish species.

4. 4

   Preopercular spine

   Like all Pomacanthus species, it possesses a strong spine on the lower margin of the preoperculum, which can be used for defense.

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