''Channichthys'' is a genus 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 ...

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 ...

Channichthyidae, the

crocodile icefish The crocodile icefish or white-blooded fish comprise a family (Channichthyidae) of notothenioid fish found in the Southern Ocean around Antarctica. They are the only known vertebrates to lack hemoglobin in their blood as adults. Icefish populatio ...

es. They are native to the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

Taxonomy

''Channichthys'' was first formally described as a genus in 1844 by the

Scottish Scottish usually refers to something of, from, or related to Scotland, including: *Scottish Gaelic, a Celtic Goidelic language of the Indo-European language family native to Scotland *Scottish English *Scottish national identity, the Scottish ide ...

naval surgeon, naturalist and

Arctic explorer Arctic exploration is the physical exploration of the Arctic region of the Earth. It refers to the historical period during which mankind has explored the region north of the Arctic Circle. Historical records suggest that humankind have explored ...

John Richardson when he described the unicorn icefish (''Channichthys rhinoceratus'') which he placed in a new

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus. Subsequently up to nine species have been classified within ''Channichthys'' which is what

FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.

does while '' Catalog of Fishes'' recognises 5 species while other authorities are of the view that the genus is monotypic and that ''C. rhinoceratus'' is the only species. The genus name is a compound of ''channos'' meaning "gape" and ''ichthys'' which means "fish", alluding to the wide gape of these fishes.

Species

The species of this genus are quite similar to each other, and reliable ways of distinguishing them include the shape of their

dorsal fins 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 ...

gill raker Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of the ...

count and relative eye diameter to snout length. * ''

Channichthys aelitae ''Channichthys'' is a genus of marine Actinopterygii, ray-finned fish belonging to the Family (biology), family Channichthyidae, the crocodile icefishes. They are native to the Southern Ocean. Taxonomy ''Channichthys'' was first formally describ ...

'' – Aelita icefish * ''

Channichthys bospori ''Channichthys'' is a genus of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. They are native to the Southern Ocean. Taxonomy ''Channichthys'' was first formally described as a genus in 1844 by the Scot ...

'' – big-eyed icefish * ''

Channichthys irinae ''Channichthys irinae,'' the pygmy icefish, is a species of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. It is endemic to the Kerguelen Islands in the Southern Ocean. Taxonomy ''Channichthys irinae'' ...

'' – pygmy icefish * ''

Channichthys mithridatis ''Channichthys mithridatis'', the green icefish, is a species of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. It is endemic to the Kerguelen Islands in the Southern Ocean. Taxonomy ''Channichthys mith ...

'' – green icefish * ''

Channichthys panticapaei ''Channichthys panticapaei'', the charcoal icefish, is a species of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. It is endemic to the Kerguelen Islands area in the Southern Ocean. This demersal species ...

'' – charcoal icefish * ''

Channichthys rhinoceratus ''Channichthys rhinoceratus,'' the unicorn icefish, is a species of marine ray-finned fish belonging to the Family (biology), family Channichthyidae, the crocodile icefishes. It is Endemism, endemic to the Kerguelen Plateau, Kerguelen-Heard Plat ...

'' – unicorn icefish * ''

Channichthys richardsoni ''Channichthys richardsoni'', the robust icefish, is a demersal species of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. It is endemic to the shelf waters of the Kerguelen Islands in the Southern Ocean. ...

'' – robust icefish * ''

Channichthys rugosus ''Channichthys'' is a genus of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. They are native to the Southern Ocean. Taxonomy ''Channichthys'' was first formally described as a genus in 1844 by the Scot ...

'' – red icefish * ''

Channichthys velifer ''Channichthys velifer'', or the sail icefish, is a species of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. It is endemic to the Kerguelen Plateau area of the Southern Ocean. This demersal species live ...

'' – sail icefish

Characteristics

''Channichthys'' icefishes may have a backwards pointing spine on the snout and small tubercles on the upper surface of the head. The operculum has 5-7 robust spines with blunt spines on the other opercular bones. They have 2

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

s which have bony plates, although they may have other plates on their flanks. In the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

the third ray is longer than the others, The first

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 ...

is tall and in large specimens the fin rays have small tubercles on them. The first and second dorsal fins are clearly separated. They have a rounded

caudal 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 ...

. They have a maximum

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

which varies from in ''C. rugosus'' to in ''C. mithridatis''.

Distribution, habitat and biology

''Channichthys'' icefishes are restricted to the Kerguelen- Heard region of the Indian sector of the Southern Ocean. They are

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

fishes. They are mainly

piscivorous A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...

but will also eat algae. They spawn in the summer and migrate into shallow water to do so.

Fisheries

''Channichthys'' icefishes, particularly ''C. rhinoceratus'', are caught as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

in botton trawls for the

mackerel icefish The mackerel icefish (''Champsocephalus gunnari'') is a benthopelagic species of fish found in the Southern Ocean and the southernmost waters of the Atlantic Ocean. They are mainly to be found near Heard and McDonald Islands, Îles Kerguelen and ...

(''Champsocephalus gunnari'').

References

{{Taxonbar, from=Q2580922 Channichthyidae Fish of the Southern Ocean