The West Australian butterflyfish (''Chaetodon assarius''), also known as the Western butterflyfish or assarius butterflyfish is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

, a

butterflyfish The butterflyfish are a group of conspicuous tropical marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. The approximately 129 species in 12 genera are found mostly on the reefs of the Atlant ...

belonging to the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Chaetodontidae. It is native to the west coast of

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Description

The West Australian butterflyfish has a pale silvery-brown coloured body with a vertical dark band running through the eye. The upper two thirds of the body are marked with 5 vertical lines of close-set dots. There is a wide brown to blackish vertical band running across the caudal peduncle and then horizontally along the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. The juveniles have an obvious black ocellus with white margins at the corner of the soft rayed part of the

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

, this is retained in young adults but is lost as they age. The spiny part of the dorsal fin holds 12–13 spines while the soft-rayed part has 21–22 rays and the anal fin has 3 spines and 18–19 soft rays. This species attains a maximum total length of .

Distribution

The West Australian butterflyfish is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

where it is found along the southern and western coast from southeast of

Israelite Bay Israelite Bay is a bay and locality on the south coast of Western Australia. Situated in the Shire of Esperance local government area, it lies east of Esperance and the Cape Arid National Park, within the Nuytsland Nature Reserve and the Grea ...

Exmouth Gulf Exmouth Gulf is a gulf in the north-west of Western Australia. It lies between North West Cape and the main coastline of Western Australia. It is considered to be part of the Pilbara Coast and Northwest Shelf, and the Carnarvon Basin geologi ...

and the

North West Shelf The North West Shelf is a continental shelf region of Western Australia. It includes an extensive petroleum, oil and natural gas, gas region off the North West Australia coast in the Pilbara region. Geology Considerable parts of the region are t ...

. it has recently been claimed to have been found in deep water in cold upwelling areas off

Bali Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nu ...

, but this is thought to be based on misidentified ''

Chaetodon guentheri ''Chaetodon guentheri'', Günther's butterflyfish or the crochet butterflyfish, is a species of marine ray-finned fish, a butterflyfish belonging to the Family (biology), family Chaetodontidae. It is native to The western Pacific Ocean. Descrip ...

''.

Habitat and biology

The West Australian butterflyfish is found over rocky reefs and sandy flats with growth off weed. It occurs in aggregations and feeds on algae and zooplankton. It is an oviparous species which forms pairs to spawn.

Systematics

The West Australian butterflyfish was first formally described in 1905 by the Australian

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

Edgar Ravenswood Waite (1866–1928) with the type locality given as between

Fremantle Fremantle () () is a port city in Western Australia, located at the mouth of the Swan River in the metropolitan area of Perth, the state capital. Fremantle Harbour serves as the port of Perth. The Western Australian vernacular diminutive for ...

and Houtman Abrolhos. The specific name ''assarius'' means “browned”, a reference to the colour and the griddle like markings. Some authorities make this species '' incertae sedis'' within the genus ''

Chaetodon ''Chaetodon'' is a tropical fish genus in the family Chaetodontidae. Like their relatives, they are known as "butterflyfish". This genus is by far the largest among the Chaetodontidae, with about 90 living species included here, though most migh ...

'' but others place it in the subgenus ''Exornator''.

References

{{Taxonbar, from=Q2330642 Chaetodon Fish described in 1905