Chaetodon assarius

Western butterflyfish
Chaetodon assarius
Chaetodon assarius, adult, Photo: Rick Stuart-Smith


Localised, Temperate Australasia


Pale beige, dark band through eye and 5 vertical rows of dark spots on body, ocellus on rear dorsal fin, rear margin of dorsal and anal fins white. Restricted range in central Western Australia.


Max Size: 13 cm

Sea Temperature Range: 17.8-28.9°C

Depth: 1-40m

Habitat Generalization Index: 0.88

Also referred to as the SGI (Species Generalisation Index), this describes the habitat niche breadth of the species. Species with values less than 15 are found in a relatively narrow range of reef habitat types (specialists), while those over 25 may be found on most hard substrates within their range (generalists). Learn more here.

Conservation and Rarity

IUCN Status: Least Concern

Occurrence: Common (45.4% of sites)

Occurrence describes how often the species is found on surveys within its distribution. It is calculated as the % of reef sites surveyed by RLS divers across all the ecoregions in which the species has been observed

Abundance: Few (2 per transect)

Abundance is calculated as the average number of individuals recorded per RLS transect, where present.

Edit by: RD Stuart-Smith, GJ Edgar, AJ Green, IV Shaw. 2015. Tropical Marine Fishes of Australia. Reed New Holland