The marbled rockcod (''Notothenia rossii'') is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

, belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Nototheniidae : ''In some scientific literature, the term "cod icefish" is used to identify members of this family. This should not be confused with the term "icefish," which refers to the "white-blooded" fishes of the family Channichthyidae. See Icefish (disam ...

, the notothens or cod icefishes. It is 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 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...

, where it can be found at depths from . This is a commercially important species.

Taxonomy

The marbled rockcod was first formally described in 1844 by the Scottish

naval surgeon A naval surgeon, or less commonly ship's doctor, is the person responsible for the health of the ship's company aboard a warship. The term appears often in reference to Royal Navy's medical personnel during the Age of Sail. Ancient uses Specialis ...

naturalist Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

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 with no type locality given, although it is thought likely to be Kerguelen Island. Richardson gave it the specific name ''rossii'' which honours

James Clark Ross Sir James Clark Ross (15 April 1800 – 3 April 1862) was a British Royal Navy officer and explorer of both the northern and southern polar regions. In the Arctic, he participated in two expeditions led by his uncle, Sir John Ross, John ...

, the leader of the

Ross expedition The Ross expedition was a voyage of scientific exploration of the Antarctic in 1839 to 1843, led by James Clark Ross, with two unusually strong warships, HMS Erebus (1826), HMS ''Erebus'' and HMS Terror (1813), HMS ''Terror''. It explored what i ...

, a scientific expedition by the vessels HMS ''Erebus'' and HMS ''Terror'' to survey and explore the coasts of Antarctica.

Description

The marbled rockcod can reach a length of , though a more common length is around . The greatest recorded weight for this species is . The

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

is divided in two parts, with four to seven spines in the front portion and 32 to 36 soft rays in the long, back portion. The

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

has 26 to 30 soft rays. The colour and pattern varies but it is typically dark brown with dark marbling on the upper body, paler on the lower body. The first dorsal fin has a dark spot in the membrane between each spine. The juveniles are yellowish or golden in colour during their benthic phase while the pelagic juveniles are silvery.

Distribution

The marbled rockcod's range includes the northern end of the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martin in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctica. ...

, the

Scotia Arc The Scotia Arc is the island arc system forming the north, east and south border of the Scotia Sea. The northern border, the North Scotia Ridge, comprises (from west to east): Isla de los Estados at the tip of Tierra del Fuego, the Burdwood, Dav ...

Prince Edward Islands The Prince Edward Islands are two small uninhabited subantarctic volcanic islands in the southern Indian Ocean that are administered by South Africa. They are named Marion Island (named after Marc-Joseph Marion du Fresne, 1724–1772) and P ...

Crozet Islands The Crozet Islands (; or, officially, ''Archipel Crozet'') are a sub-Antarctic archipelago of small islands in the southern Indian Ocean. They form one of the five administrative districts of the French Southern and Antarctic Lands. History ...

Kerguelen Islands The Kerguelen Islands ( or ; in French commonly ' but officially ', ), also known as the Desolation Islands (' in French), are a group of islands in the subantarctic, sub-Antarctic region. They are among the Extremes on Earth#Remoteness, most i ...

Heard Island The Territory of Heard Island and McDonald Islands (HIMI) is an Australian external territory comprising a volcanic group of mostly barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall land ...

and

Macquarie Island Macquarie Island is a subantarctic island in the south-western Pacific Ocean, about halfway between New Zealand and Antarctica. It has been governed as a part of Tasmania, Australia, since 1880. It became a Protected areas of Tasmania, Tasmania ...

, as well as the Ob Bank, and Lena Bank.

Biology

Marbled rockcod females become sexually mature at about six years of age. Along with mature males they move into the deeper water of the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

. Spawning takes place once a year and the young fish stay mostly in shallow water in the fiords and bays, feeding mainly on

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

. Males can live for up to twelve years.

Fisheries

The marbled rockcod was heavily fished by

Soviet The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

fishers during the 1960s and 1970s, with catches exceeding 100,000 tonnes in some seasons; it almost disappeared from around

South Georgia Island South Georgia is an island in the Atlantic Ocean, South Atlantic Ocean that is part of the British Overseas Territories, British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. ...

, and by 1980, was depleted throughout the Southern Ocean. It took the population 20 years to show signs of recovery.

References

* Tony Ayling & Geoffrey Cox, ''Collins Guide to the Sea Fishes of New Zealand'', (William Collins Publishers Ltd, Auckland, New Zealand 1982) {{DEFAULTSORT:Marbled rockcod Notothenia Fish of the Southern Ocean Fauna of the Crozet Islands Fauna of the Kerguelen Islands Fauna of Heard Island and McDonald Islands Fish described in 1844 Taxa named by John Richardson (naturalist)