Triangle butterflyfish (Chaetodon triangulum)

Classification (WoRMS)

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

Accepted name: Chaetodon triangulum · Authority: Cuvier, 1831 · Taxonomic status: accepted · AphiaID: 218748.

Synonyms and superseded combinations recorded for this taxon: Gonochaetodon triangulum (Cuvier, 1831).

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=218748 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (FishBase)

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

Maximum length: 16 cm · Habitat zone: reef-associated · Body shape: short and / or deep · Vulnerability index: 10 of 100 · Fishery importance: commercial · Aquarium trade: commercial.

FishBase notes: Inhabit lagoon and seaward reefs (Ref. 9710). Closely associated with Acropora corals, particularly the staghorn variety. Territorial and in pairs (Ref. 9710). Juveniles solitary among coral branches (Ref. 48636).

Feed mainly on coral polyps and therefore does not adjust easily to aquarium conditions. Oviparous (Ref. 205), monogamous (Ref. 52884). Form pairs during breeding (Ref. 205).

Source: FishBase species summary (SpecCode 7805) — https://www.fishbase.se/summary/Chaetodon-triangulum.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

291 georeferenced occurrence records for Chaetodon triangulum are published through GBIF from 13 countries or marine areas. The map above plots 63 distinct locations from a sample of 291 records, omitting 14 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: Thailand (104); Maldives (90); India (31); Philippines (20); Indonesia (18); Solomon Islands (10); Palau (8); Malaysia (3); Fiji (2); Papua New Guinea (2); Sri Lanka (1); Viet Nam (1); Vanuatu (1).

Marine regions with a valid WoRMS distribution record: Seychellois Exclusive Economic Zone; Madagascar; Chagos.

Source: GBIF Occurrence Search (taxonKey 10675465) — https://www.gbif.org/occurrence/search?taxon_key=10675465&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=218748 (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 Chaetodon triangulum 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 165624) — https://www.iucnredlist.org/species/165624/0; GBIF IUCN Red List category endpoint (taxonKey 10675465) — https://api.gbif.org/v1/species/10675465/iucnRedListCategory. Accessed 2026-09-25.

Description and natural history (Wikipedia)

Chaetodon triangulum has a flat triangular shaped body, emphasised when the fins are fully spread, and an elongated snout. Its body is predominantly whitish in colour with many broad, vertical grey chevron-shaped bands along the sides, Its mouth is orange, and there is a brownish orange vertical band through the eye, which grows brighter orange closer to the top of the head widening as it extends rearward on the base of the dorsal fin in adults.

The caudal peduncle is black, as is the caudal fin but its margins are yellow. The dorsal fin has 11-12 spines and 23-26 soft rays while the anal fin contains 3 spines and 20-21 soft rays. This species attains a maximum total length of 16 cm.

Chaetodon triangulum has a wide distribution in the Indian Ocean from the coast of tropical East Africa east to the Andaman Sea and along the Indian Ocean coastlines of Sumatra and Java. It also appears at the Seribu Islands and has been reported near Bali.

Chaetodon triangulum is found in lagoon and seaward reefs where it is strongly associated with corals in the genus Acropora, especially staghorn corals. This is a territorial species which lives in pairs, although solitary juveniles hide among coral branches. Triangle butterflyfish are obligate corallivores that feed primarily on Acropora corals. They defend patches of these corals and actively chase other butterflyfishes from these territories and the food supply it contains.

Chaetodon triangulum was first formally described in 1831 by the French anatomist Georges Cuvier (1769-1832) with the type locality given as Jakarta.

Source: Wikipedia: Chaetodon triangulum — https://en.wikipedia.org/wiki/Chaetodon_triangulum (CC BY-SA 4.0). Accessed 2026-09-25.