Semicircle angelfish (Pomacanthus semicirculatus)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Acanthuriformes · Family: Pomacanthidae · Genus: Pomacanthus.

Accepted name: Pomacanthus semicirculatus · Authority: (Cuvier, 1831) · Taxonomic status: accepted · AphiaID: 220003.

Synonyms and superseded combinations recorded for this taxon: Holacanthus alternans Cuvier, 1831; Holacanthus ignatius Playfair, 1868; Holacanthus lepidolepis Bleeker, 1853; Holacanthus reginae Liénard, 1891; Holacanthus semicirculatus Cuvier, 1831; Pomacanthops alternans Cuv., 1831; Pomacanthops caeruleus (Ehren) Cuv., 1831; Pomacanthops ignatius (Playfair, 1868); Pomacanthops lasti von Bonde, 1934; Pomacanthops poecilus Peters, 1868; Pomacanthops reginae (Lienard) Sauvage, 1891; Pomacanthops semicirculatus (Cuvier, 1831); Pomacanthus semicircularis (Cuvier, 1831).

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=220003 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (FishBase)

Measured values published by FishBase for Pomacanthus semicirculatus. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 40 cm · Depth range: 1–40 m · Habitat zone: reef-associated · Body shape: short and / or deep · Vulnerability index: 38.8 of 100 · Fishery importance: minor commercial · Aquarium trade: commercial.

FishBase notes: Juveniles inhabit shallow protected areas, while adults prefer coastal reefs with heavy coral growth providing ample hiding places. Generally solitary or in pairs. Feeds on sponges, tunicates, and algae (Ref. 30573). The young are excellent aquarium fish and suitable for a community tank.

Source: FishBase species summary (SpecCode 5663) — https://www.fishbase.se/summary/Pomacanthus-semicirculatus.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

2,801 georeferenced occurrence records for Pomacanthus semicirculatus are published through GBIF from 40 countries or marine areas. The map above plots 366 distinct locations from a sample of 2,801 records, omitting 70 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Australia (1,230); Indonesia (258); Chinese Taipei (223); Seychelles (150); Japan (132).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 2396399) — https://www.gbif.org/occurrence/search?taxon_key=2396399&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=220003 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Conservation status (IUCN Red List)

The IUCN Red List assesses Pomacanthus semicirculatus (Cuvier, 1831) as Least Concern (code LC). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 165851) — https://www.iucnredlist.org/species/165851/0; GBIF IUCN Red List category endpoint (taxonKey 2396399) — https://api.gbif.org/v1/species/2396399/iucnRedListCategory. Accessed 2026-09-25.

Description and natural history (Wikipedia)

Pomacanthus semicirculatus, like other members of the genus Pomacanthus has adults and juveniles which are very different from each other. The adults are brownish green in colour with the scales edged in blue creating a blue speckling over the body and tail. All of the fins, apart from the plain yellow pectoral fins, have blue margins. There are long, filamentous growths from the dorsal and anal fins.

The juveniles in contrast, are blue-black marked from top to bottom with narrow white stripes. At the head end the stripes are fairly straight but they become increasingly curved as they approach the base of the tail. The juveniles gradually adopt the adult colouration when they are 8 to 16 cm.

The dorsal fin contains 13 spines and 20–23 soft rays while the anal fin contains 3 spines and 18–22 soft rays. This species attains a maximum total length of 40 cm.

Distribution

Pomacanthus semicirculatus is found in the Indo-Pacific region. Its range extends from the eastern coast of Africa from the southern Red Sea coast of Sudan south as far as South Africa. It then occurs east across the Indian and Pacific Oceans to Fiji, Tonga and Samoa.It occurs as far north as southern Japan and south to Australia.

Within the Australian EEZ this species is widespread from the Houtman Abrolhos of Western Australia around the coast to as far south on the eastern coast as Sydney, juveniles extending farther south to Merimbula. It is also found at Christmas Island, the Cocos (Keeling) Islands as well as Lord Howe Island in the Tasman Sea. It has also been seen sporadically off the east coast of Florida since 1999 and at Oahu, Hawaii since 2005.

Habitat and biology

Pomacanthus semicirculatus is found at depths between 1 and 40 m on sheltered coral reefs, where it feeds on algae, tunicates and sponges. The juveniles are very timid and difficult to approach.

The juveniles occur in shallow sheltered areas, while adults show a preference for coastal reefs where there is rich coral growth which give the fish plenty of places to hide. It is typically encountered in pairs or as solitary individuals. The adults have been recorded from wrecks.

Systematics

Pomacanthus semicirculatus was first formally described as Holacanthus semicirculatus in 1831 by the French anatomist Georges Cuvier (1769–1832) with the type locality given as Timor, Bourou, Waigeo, Indonesia, and Port Praslin, New Ireland Island, Bismarck Archipelago in Papua New Guinea. Some authorities place this species in the subgenus Arusetta. The specific name semicirculatus means "semicircular", a reference to the semicircular slender blue and white lines on the rear of the body on juveniles, which are lost on the adults.

Utilisation

Pomacanthus semicirculatus is frequently encountered in the aquarium trade.

Source: Wikipedia: Pomacanthus semicirculatus — https://en.wikipedia.org/wiki/Pomacanthus_semicirculatus (CC BY-SA 4.0). Accessed 2026-09-25.