''Channichthys rhinoceratus,'' the unicorn icefish, is a species of marine ray-finned fish belonging to the family Channichthyidae, the crocodile icefishes. It is endemic to the Kerguelen-Heard Plateau in the Southern Ocean. It is a

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 ...

species living from surface waters to depths up to . It is considered by some researchers as the only species in the genus ''

Channichthys ''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 ...

.''

Description

Described by Sir John Richardson in 1844 and being the type species of the genus ''

'', the unicorn icefish is generally pale brown, though smaller specimens have four dark cross-bars present on each side of the body, and dark spots are present on the body, sometimes with reddish patches and dark reticulations are present. Dark spots may be present on the blackish first dorsal fin. Other fins are colored pale or dusky. It grows up to a maximum length of 60 cm (24 inches) and a maximum published weight of 0.5 kg (1.1 lbs). A more common length is 40 cm (16 inches). Its size (being the largest of the ''Channichthys'' species) and the fact that it has the smallest eye diameter relative to snout length of the ''Channichthys'' species (28% to 31.6 %) distinguish it from its congeners. The large interorbital space of this species should also help distinguish it from '' C. irinae, C. bospori'' and ''C. mithridatis''.

Biology

This species is a typical benthic predator that feeds on

fishes Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

(other notothenoids, especially 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'' and other ''Channichthys'' species, however, ''

Harpagifer ''Harpagifer'', the spiny plunderfishes is a genus of marine ray-finned fishes, belonging to the family Harpagiferidae, it is the only genus in this monotypic family. They are found in the Southern Ocean. Taxonomy The genus ''Harpagifer'' was de ...

'' fishes are also taken) and occasionally

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

. It is itself preyed on by the black-browed albatross ''(Thalassarche melanophris)''. Sexual maturity is reached when it is around in length. This species migrates to shallower waters in January and lays 6,000 to 14,000 eggs in February. The spent fish return to deeper water in June. Although this species seems to be endemic to the Kerguelen-Heard Plateau, otoliths of this species have been found in the stomach contents of

gentoo penguins The gentoo penguin ( ) (''Pygoscelis papua'') is a penguin species (or possibly a species complex) in the genus ''Pygoscelis'', most closely related to the Adélie penguin (''P. adeliae'') and the chinstrap penguin (''P. antarcticus''). The earli ...

nesting on

Marion Island The Prince Edward Islands are two small uninhabited islands in the sub-Antarctic Indian Ocean that are part of South Africa. The islands are named Marion Island (named after Marc-Joseph Marion du Fresne, 1724–1772) and Prince Edward Island ...

, seemingly confirming its presence there. However, there is insufficient data to prove that this species is a resident there and not just an occasional visitor. A known predator of this species is the black-browed albatross ''(Thalassarche melanophris).''

Uses

Its flesh is of good quality, though not as good as that of the

, and is of minor importance to commercial fisheries, caught in bottom trawls for mackerel icefish as a

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 ...

species. Total catches amounted to 80 tonnes (88 tons) in 2010. This has increased to 151 tonnes (166 tons) in 2019. However, this was still much less than the 1,663 tonnes (1,833 tons) allowed for that year.

References

{{Taxonbar, from=Q2436631 rhinoceratus Fish of the Southern Ocean Fish described in 1844 Fauna of the Kerguelen Islands