Semicircle Angelfish

The semicircle angelfish is a large marine angelfish of the Indo-West Pacific. It is found from the Red Sea and East Africa across to the islands of the western Pacific, north to southern Japan and south around Australia. Like other angelfish in its genus, the young and the adults look so different that they were once easy to mistake for two species. It feeds on sponges, sea squirts and algae. It is usually seen alone or in pairs, between 1 and 40 m.

Also known as: koran angelfish, half-circled angelfish, zebra angel-fish, blue angelfish, blue angel, semicircle anglefish

Juveniles and adults look so different that they were once catalogued as separate species. To place which stage you are seeing, use just one cue for each: the curving white stripes for a juvenile, or the yellow-tipped trailing fin threads for an adult.

Adults are brownish green, with each scale edged in blue so that the whole body and tail look speckled with blue. All the fins carry blue edges except the pectoral fins on the sides, which are plain yellow. The rear parts of the fin on the back and the fin underneath are drawn out into long trailing threads with bright yellow tips. Juveniles look completely different: blue-black, marked from top to bottom with narrow white lines. Near the head these lines are almost straight, and they curve more and more towards the base of the tail. The adult pattern replaces the juvenile one as the fish grows.

It lives on sheltered coral reefs. Adults prefer coastal reef with heavy coral growth, which gives them plenty of holes to disappear into, and they have also been recorded on wrecks. Juveniles keep to shallow, protected water and are very shy, which makes them hard to get near.

• 

  Angelfish

  angelfish

• 

  Bicolor angelfish

  Centropyge bicolor

• 

  Cortez Angelfish

  Pomacanthus zonipectus

• 

  Emperor angelfish

  Pomacanthus imperator

• 

  French Angelfish

  Pomacanthus paru

• 

  Grey Angelfish

  Pomacanthus arcuatus