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The largehead hairtail (''Trichiurus lepturus'') or beltfish is a member of the cutlassfish family, Trichiuridae. This common to abundant species is found in tropical and temperate oceans throughout the world. The taxonomy is not fully resolved, and the Atlantic, East Pacific and Northwest Pacific populations are also known as Atlantic cutlassfish, Pacific cutlassfish and Japanese cutlassfish, respectively. This predatory, elongated fish supports major fisheries.


Appearance

Largehead hairtails are silvery steel blue in color, turning silvery gray after death. The fins are generally semi-transparent and may have a yellowish tinge. Largehead hairtails are elongated in shape with a thin pointed tail (they lack a fish tail in the usual form). The eyes are large, and the large mouth contains long pointed fang-like teeth. Largehead hairtails grow to in weight, and in length. Most are only long, although they regularly reach in Australia.


Range and habitat

Largehead hairtails are found worldwide in tropical and temperate oceans. In the East Atlantic they range from southern United Kingdom to South Africa, including the Mediterranean Sea. In the West Atlantic it ranges from
Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...
(occasionally
Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of mainland Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer mont ...
) to northern Argentina, including the Caribbean Sea and Gulf of Mexico. In the East Pacific they range from southern
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
to Peru. Widespread in the Indo-Pacific region, ranging from the Red Sea to South Africa, Japan, the entire coast of Australia (except Tasmania and Victoria) and
Fiji Fiji ( , ,; fj, Viti, ; Fiji Hindi: फ़िजी, ''Fijī''), officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consis ...
, they are absent from the central Pacific Ocean, including
Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
. Some populations are migratory. A study of largehead hairtails in southern Japan's
Bungo Channel The is a strait separating the Japanese islands of Kyushu and Shikoku. It connects the Pacific Ocean and the Seto Inland Sea on the western end of Shikoku. The narrowest part of this channel is the Hōyo Strait. In the English-speaking world, ...
indicated that the optimum water temperature is . Based on fishing catches in the Jeju Strait of South Korea, the species resides mainly in water warmer than , while catches are poor in colder water. Off southern Brazil it mainly occurs in waters warmer than . It is absent from waters below . The largehead hairtail prefers relatively shallow coastal regions over muddy bottoms, but it sometimes enters estuaries and has been recorded at depths of . In European waters, most records are from , Off southern Brazil hairtails are most abundant between , they have been recorded between in the East Pacific, and in southern Japan's Bungo Channel they are primarily known from but most common between . They are mainly benthopelagic, but may appear at the surface during the night.


Taxonomy

Although often considered a single highly widespread species, it has been argued that it is a species complex that includes several species with the main groups being in the Atlantic (Atlantic cutlassfish), East Pacific (Pacific cutlassfish), Northwest Pacific (Japanese cutlassfish) and Indo-Pacific. If split, the Atlantic would retain the scientific name ''T. lepturus'', as the type locality is off South Carolina. The Northwest Pacific ( Sea of Japan and East China Sea) differs in
morphometric Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are c ...
s, meristics and genetics, and is sometimes recognized as ''T. japonicus''. Morphometric and meristic differences have also been shown in the population of the East Pacific (California to Peru), leading some to recognize it as ''T. nitens''. Neither ''T. japonicus'' nor ''T. nitens'' are recognized as separate species by FishBase where considered
synonyms A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are ...
of ''T. lepturus'', but they are recognized as separate species by the Catalog of Fishes. The IUCN recognizes the East Atlantic population as a distinct, currently undescribed species. This is based on genetic evidence showing a
divergence In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the quantity of the vector field's source at each point. More technically, the divergence represents the volume density of ...
between West and East Atlantic populations. However, this would require that ''T. japonicus'', ''T. nitens'' and the Indo-Pacific populations also are recognized as separate species, effectively limiting ''T. lepturus'' to the West Atlantic (contrary to IUCN), as they all show a greater divergence. Additional studies are required on the possible separation and
nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. The principles of naming vary from the relatively informal conventions of everyday speech to the internationally ag ...
of the Indo-Pacific populations. Based on studies of mtDNA, which however lacked any samples from the southern parts of the Pacific and Indian Oceans, there are three species in the Indo-Pacific: ''T. japonicus'' (marginal in the region, see range above), ''T. lepturus'' (West Pacific and Eastern Indian Ocean; the species also found in the Atlantic) and the final preliminarily referred to as ''Trichiurus'' sp. 2 (Indian Ocean, and East and
South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Ph ...
s). It is likely that ''Trichiurus'' sp. 2 equals '' T. nanhaiensis''. The names ''T. coxii'' and ''T. haumela'' have been used for the populations off Australia and in the Indo-Pacific, respectively, but firm evidence supporting their validity as species is lacking.


Behavior and life cycle

Juveniles participate in the diel vertical migration, rising to feed on krill and small fish during the night and returning to the sea bed in the day. This movement pattern is reversed by large adults, which mainly feed on fish. Other known prey items include squid and shrimp, and the highly carnivorous adults regularly cannibalise younger individuals. Largehead hairtails are often found in large, dense schools. Spawning depends on temperature as the larvae prefer water warmer than and are entirely absent at less than . Consequently, spawning is year-round in tropical regions, but generally in the spring and summer in colder regions. Through a spawning season each female lays many thousand pelagic eggs that hatch after three to six days. In the Sea of Japan most individuals reach maturity when two years old, but some already after one year. The oldest recorded age is 15 years.


Fisheries and usage

Largehead hairtail is a major commercial species. With reported landings of more than 1.3 million tonnes in 2009, it was the sixth most important captured fish species. The species is caught throughout much of its range, typically by bottom trawls or beach seines, but also using a wide range of other methods. In 2009, by far the largest catches (1.2 million tonnes) were reported by China and Taiwan from the Northwest Pacific ( FAO Fishing Area 61). The next largest catches were reported from South Korea, Japan, and Pakistan. Some of the numerous other countries where regularly caught include Angola, Nigeria, Senegal, Mauritania, Morocco, Brazil, Trinidad, Colombia, Mexico, southeastern United States, Iran, India, and Australia. In Korea, the largehead hairtail is called ''galchi'' (), in which ''gal'' () came from
Middle Korean Middle Korean is the period in the history of the Korean language succeeding Old Korean and yielding in 1600 to the Modern period. The boundary between the Old and Middle periods is traditionally identified with the establishment of Goryeo in 9 ...
''galh'' () meaning "sword" and ''-chi'' () is a suffix for "fish". It is popular for frying or grilling. In Japan, where it is known as ''tachiuo'' (" (tachi)": sword, " (uo)":fish), they are fished for food and eaten grilled or raw, as sashimi. They are also called "sword-fish" in Portugal and Brazil (''peixe-espada''), where they are eaten grilled or fried. Its flesh is firm yet tender when cooked, with a moderate level of "fishiness" to the smell and a low level of oiliness. The largehead hairtail is also notable for being fairly easy to debone. Trichiurus lepturus FishMarketInTokyo.JPG, Largehead hairtails at a fish market in
Tokyo Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, with an estimated 37.46 ...
Galchi-gui.jpg, ''Galchi-
gui The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...
'' (grilled largehead hairtail) Galchi-hoe.jpg, ''Galchi-
hoe Hoe or HOE may refer to: * Hoe (food), a Korean dish of raw fish * Hoe (letter), a Georgian letter * Hoe (tool), a hand tool used in gardening and farming ** Hoe-farming, a term for primitive forms of agriculture * Backhoe, a piece of excavating ...
'' (raw largehead hairtail) Galchi-jorim.jpg, ''Galchi-
jorim ''Jorim'' () is a simmered Korean dish, made by boiling vegetables, meat, fish, seafood, or tofu in seasoned broth until the liquid is absorbed into the ingredients and reduced down. ''Jorim'' dishes are usually soy sauce-based, but gochu ...
'' (simmered largehead hairtail) Keripik Ikan Beledang - IMG 20220211 133740 620.jpg, '' Kripik Beledang'' (battered and deep-fried hairtail) from Bengkulu, Indonesia


References


External links

* {{Authority control largehead hairtail Fish of the Atlantic Ocean Fish of the Pacific Ocean Fish of Japan Cosmopolitan fish largehead hairtail largehead hairtail