Margined coralfish (Chelmon marginalis)
Source-cited species reference: taxonomy from WoRMS, biology from FishBase, occurrence map from GBIF, conservation from IUCN Red List, description from Wikipedia.
Chelmon marginalis, the margined coralfish or Western beaked butterflyfish, is a species of marine ray-finned fish, a butterflyfish in the family Chaetodontidae. It is a reef fish which is endemic to Australia.
- Scientific name
- Chelmon marginalis
- Authority
- Richardson, 1842
- Family
- Chaetodontidae
- Order
- Acanthuriformes
- Maximum length
- 18 cm
- Depth range
- 1–30 m
- Habitat zone
- reef-associated
- Iucn red list
- Least Concern
- Gbif occurrence records
- 1,726
Classification (WoRMS)
Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Acanthuriformes · Family: Chaetodontidae · Genus: Chelmon.
Accepted name: Chelmon marginalis · Authority: Richardson, 1842 · Taxonomic status: accepted · AphiaID: 278682.
Synonyms and superseded combinations recorded for this taxon: Chelmo tricinctus Castelnau, 1875; Chelmon rostratus marginalis Richardson, 1842.
Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=278682 (CC BY 4.0). Accessed 2026-09-23.
Biology and life history (FishBase)
Measured values published by FishBase for Chelmon marginalis. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.
Maximum length: 18 cm · Depth range: 1–30 m · Habitat zone: reef-associated · Body shape: short and / or deep · Vulnerability index: 10 of 100 · Fishery importance: commercial · Aquarium trade: commercial.
FishBase notes: Inhabit coastal reefs (Ref. 9710). Usually solitary. Oviparous (Ref. 205). Form pairs during breeding (Ref. 205).
Source: FishBase species summary (SpecCode 6650) — https://www.fishbase.se/summary/Chelmon-marginalis.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.
Distribution and occurrence records (GBIF)
1,726 georeferenced occurrence records for Chelmon marginalis are published through GBIF from 4 countries or marine areas. The map above plots 125 distinct locations from a sample of 1,726 records, omitting 9 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 (1,716); Papua New Guinea (5); Indonesia (4); Philippines (1).
The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.
Source: GBIF Occurrence Search (taxonKey 5209923) — https://www.gbif.org/occurrence/search?taxon_key=5209923&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=278682 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.
Conservation status (IUCN Red List)
The IUCN Red List assesses Chelmon marginalis Richardson, 1842 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 165616) — https://www.iucnredlist.org/species/165616/0; GBIF IUCN Red List category endpoint (taxonKey 5209923) — https://api.gbif.org/v1/species/5209923/iucnRedListCategory. Accessed 2026-09-23.
Description and natural history (Wikipedia)
Chelmon marginalis is silvery white in colour with two slender orange bars on the head and front part of the body, and a wide yellowish or yellowish-orange band close to the caudal peduncle. The adults do not have a false eyespot or ocellus on their dorsal fin. The juveniles have a bar towards the tail and an ocellus on the dorsal fin, these fade and eventually disappear as the fish matures. The dorsal fin contains 9-10 spines and 29-33 soft rays while the anal fin has 3 spines and 21-22 soft rays. This species attains a maximum total length of 18 cm.
Chelmon marginalis is endemic to Australia where it is found from the Houtman Abrolhos in Western Australia around the coasts of northern Australia to the northern Great Barrier Reef and the reefs in the Coral Sea off Queensland.
Chelmon marginalis is found largely on coastal coral and rocky reefs, it can be found on the outer reef slopes, drop off and around islands close to the shore as well. It is a carnivorous species which preys on benthic invertebrates such as crabs, shrimps and polychaetes. This is normally a solitary species which forms pairs to breed, breeding is oviparous.
Chelmon marginalis is rarely exported and is thus uncommon in the aquarium trade.
Chelmon marginalis was first formally described in 1842 by the Scottish naval surgeon, arctic explorer and naturalist Sir John Richardson (1787-1865) with the type locality given as Port Essington in the Northern Territory.
Source: Wikipedia: Chelmon marginalis — https://en.wikipedia.org/wiki/Chelmon_marginalis (CC BY-SA 4.0). Accessed 2026-09-23.
Frequently Asked Questions
What is the Margined coralfish (Chelmon marginalis)?
It is a small, reef-associated butterflyfish in the family Chaetodontidae, originally described by Richardson in 1842. You will also see it referred to as the Western beaked butterflyfish.
Where does the Margined coralfish live?
This species is endemic to Australian waters, meaning it is not found in the wild anywhere else on Earth. It occupies coral reef habitats at depths between roughly 1 and 30 metres.
How big does a Margined coralfish get?
Adults top out at about 18 centimetres in total length, which places it among the smaller butterflyfish species. Its compact size suits life among the tighter nooks of reef structures.
What is the Margined coralfish's full taxonomic placement?
It belongs to the order Acanthuriformes and the family Chaetodontidae, grouping it with other ray-finned butterflyfish. The binomial name Chelmon marginalis was established by Richardson in 1842.
Why is the Margined coralfish of particular interest to reef enthusiasts?
Because it is restricted to Australian reefs, it stands out among butterflyfish relatives that typically enjoy a much wider Indo-Pacific range. That narrow distribution makes it a focal species for Australian marine biodiversity studies and local aquarists.
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