The black ruff (''Centrolophus niger'') is a medusafish, the only member of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...

''Centrolophus''. It is a

bathypelagic fish Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that do live on or near the bottom, and reef fish that are associated with coral reef ...

found in all tropical and

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

oceans at depths of . Its length is typically up to , but it may reach . Other common names include rudderfish and blackfish.

Description

The black ruff has a robust

fusiform Fusiform means having a spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon-shape, but often implies a focal broadening of a structure that continues from one or both ends, such as an aneurysm on a ...

body shape. Its maximum length is but a more common length is . 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 co ...

has five spines and 37 to 41

soft rays Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology c ...

, 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 s ...

has three spines and 20 to 24 soft rays. The bases of these fins have a fleshy sheath clad with scales that partially conceals the rays. The head is grey and the body colour violet-black, dark brown or purplish, with a paler belly. The fins are darker than the body colour. Sometimes there are indistinct spots or a marbled pattern.

Distribution and habitat

The black ruff is known from the northwestern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

, where its range extends from Nova Scotia to Massachusetts, the northeastern Atlantic and the Mediterranean Sea; also from the southeastern Atlantic and the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

, its range including South Africa and Australia and New Zealand, as well as the Southern Ocean. It is a

bathypelagic The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagi ...

fish with a depth range of , but is usually found within the range . It is largely absent from the tropics. It is occasionally found in the waters around the British Isles, where it has been recorded off

County Galway "Righteousness and Justice" , anthem = () , image_map = Island of Ireland location map Galway.svg , map_caption = Location in Ireland , area_footnotes = , area_total_km2 = ...

, County Donegal and the

Isles of Scilly The Isles of Scilly (; kw, Syllan, ', or ) is an archipelago off the southwestern tip of Cornwall, England. One of the islands, St Agnes, is the most southerly point in Britain, being over further south than the most southerly point of th ...

. In 1901, a specimen was caught in a salmon net in the

Firth of Forth The Firth of Forth () is the estuary, or firth, of several Scottish rivers including the River Forth. It meets the North Sea with Fife on the north coast and Lothian on the south. Name ''Firth'' is a cognate of ''fjord'', a Norse word meanin ...

and was presented to the Edinburgh Museum.

Ecology

Juvenile fish live in surface waters but adults live at greater depths where they may form small schools. The diet consists mainly of small fish, squid, large crustaceans, and any other animals that may be encountered in mid-ocean.

References

* * Tony Ayling & Geoffrey Cox, ''Collins Guide to the Sea Fishes of New Zealand'', (William Collins Publishers Ltd, Auckland, New Zealand 1982) {{Taxonbar, from=Q2000476 Centrolophidae Fish of Hawaii Fish of the Atlantic Ocean Fish of the Indian Ocean Monotypic fish genera Fish described in 1789