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or more specifically , are colored varieties of the Amur carp (''
Cyprinus rubrofuscus ''Cyprinus rubrofuscus'', the Amur carp, is a species of cyprinid fish, and is the wild form of the well-known koi. It is widespread in the fresh waters of eastern Asia, native to China, Vietnam and Laos from the Amur to Red River basins, and ...
'') that are kept for decorative purposes in outdoor
koi pond Koi ponds are ponds used for holding koi carp, usually as part of a garden. Koi ponds can be designed specifically to promote health and growth of the Nishikigoi or Japanese Ornamental Carp. Koi ponds or lakes are a traditional feature of Jap ...
s or
water garden Water garden or aquatic garden, is a term sometimes used for gardens, or parts of gardens, where any type of water feature is a principal or dominant element. The primary focus is on plants, but they will sometimes also house waterfowl, or orn ...
s. Koi is an informal name for the colored variants of ''C. rubrofuscus'' kept for ornamental purposes. There are many varieties of ornamental koi, originating from breeding that began in
Niigata, Japan is a Prefectures of Japan, prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,227,496 (1 July 2019) and is the List of Japanese prefectures by area, fifth-largest prefecture of Japan by geographic area ...
in the early 19th century.Japanese Ornamental Koi Carp: Origin, Variation and Genetics
May 2015

/ref> Several varieties are recognized by the Japanese, distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, orange, yellow, blue, brown and cream, besides metallic shades like gold and silver-white ('platinum') scales. The most popular category of koi is the ''Gosanke'', which is made up of the ''Kōhaku'', ''Taishō Sanshoku'' and ''Shōwa Sanshoku'' varieties.


History

Carp are a large group of fish originally found in
Central Europe Central Europe is an area of Europe between Western Europe and Eastern Europe, based on a common historical, social and cultural identity. The Thirty Years' War (1618–1648) between Catholicism and Protestantism significantly shaped the a ...
and
Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...
. Various carp species were originally
domesticated Domestication is a sustained multi-generational relationship in which humans assume a significant degree of control over the reproduction and care of another group of organisms to secure a more predictable supply of resources from that group. A ...
in China, where they were used as food fish. Carp are
coldwater fish Coldwater fish can have different meanings in different contexts. In the context of aquariums, it refers to fish species that do not require a heater to remain within tolerable temperatures in a typical indoor aquarium. However, most or all ornam ...
, and their ability to survive and adapt to many climates and water conditions allowed the domesticated species to be propagated to many new locations, including Japan. Natural color mutations of these carp would have occurred across all populations. Chinese Jin Dynasty (fourth century AD) texts mentioned carp of various colors. The oldest mention of colored carp in Japan is found in the Japanese history book '' Nihon Shoki'' (Chronicles of Japan) completed in 720. According to the ''Nihon shoki'', it is recorded that
Emperor Keikō , also known as and , was the 12th legendary Emperor of Japan, according to the traditional order of succession. Both the ''Kojiki'', and the ''Nihon Shoki'' (collectively known as the ''Kiki'') record events that took place during Keikō's all ...
praised colored carp in a pond in the Mino region in 94 and that
Emperor Suiko (554 – 15 April 628) was the 33rd monarch of Japan,Imperial Household Agency (''Kunaichō'') 推古天皇 (33)/ref> according to the traditional order of succession. Suiko reigned from 593 until her death in 628. In the history of Japan, ...
saw them in the garden of
Soga no Umako was the son of Soga no Iname and a member of the powerful Soga clan of Japan. Umako conducted political reforms with Prince Shōtoku during the rules of Emperor Bidatsu and Empress Suiko and established the Soga clan's stronghold in the go ...
's residence in 620. Carp were first bred for color mutations in China more than a thousand years ago, where
selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant m ...
of colored varieties led to the development of the
goldfish The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the wild have bec ...
(''Carassius auratus''). The Amur carp (''
Cyprinus rubrofuscus ''Cyprinus rubrofuscus'', the Amur carp, is a species of cyprinid fish, and is the wild form of the well-known koi. It is widespread in the fresh waters of eastern Asia, native to China, Vietnam and Laos from the Amur to Red River basins, and ...
'') is a member of the cyprinid family
species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
native to
East Asia East Asia is the eastern region of Asia, which is defined in both Geography, geographical and culture, ethno-cultural terms. The modern State (polity), states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. ...
. Amur carp were previously identified as a subspecies of the common carp (as ''C. c. haematopterus''), but recent authorities treat it as a separate species under the name ''C. rubrofuscus''. Amur carp have been aquacultured as a food fish at least as long ago as the fifth century BC in China. The systematic breeding of ornamental Amur carp began in the 1820s, in Ojiya and Yamakoshi in the
Niigata Prefecture is a prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,227,496 (1 July 2019) and is the fifth-largest prefecture of Japan by geographic area at . Niigata Prefecture borders Toyama Prefecture and ...
(located on the northeastern coast of
Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island se ...
) in Japan. Selective breeding gave rise first to red carp, then to pale blue ''Asagi'' and white, red, and yellow ''Bekkou''. The ''Sarasa'' variety, with a red on white pattern, was created around 1830. Later, a yellow-based ''Ki utsuri'' variety was born. From this original handful of koi varieties, all other Nishikigoi varieties were bred, with the exception of the Ogon variety (single-colored, metallic koi), which was developed relatively recently. The outside world was unaware of the development of color variations in Japanese koi until 1914 when the Niigata koi were exhibited at an annual exposition in
Tokyo Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and List of cities in Japan, largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, ...
. From that time, interest in koi spread throughout Japan. The number of varieties continued to grow, and repeated cross-breeding gave rise to more flashy varieties, such as ''
Kōhaku Kōhaku is a Japanese word that can mean one of several things depending on the Kanji used. Examples: *紅白: means "red and white." *黄白: means "gold and silver" or "yellow and white." Kōhaku (紅白) may refer to: * Kōhaku maku, a red an ...
'', ''Taishō Sanshoku'' and ''Shōwa Sanshoku''.The History of Nishikigoi
Zen Nippon Airinkai
The hobby of keeping koi eventually spread worldwide. They are sold in many pet aquarium shops, with higher-quality fish available from specialist dealers. Collecting koi has become a social hobby. Passionate hobbyists join clubs, share their knowledge and help each other with their koi. In particular, since the 21st century, some wealthy Chinese have imported large quantities of koi from Niigata in Japan, and the price of high-quality carp has soared. In 2018, one carp was bought by a Chinese collector for about $2 million, the highest price ever. There are also cases in which purchased carp are bred in China and sold to foreign countries, and many breeds are spreading all over the world.


Etymology

The words "koi" and "nishikigoi" come from the Japanese words 鯉 (carp), and 錦鯉 (brocaded carp), respectively. In Japanese, "koi" is a
homophone A homophone () is a word that is pronounced the same (to varying extent) as another word but differs in meaning. A ''homophone'' may also differ in spelling. The two words may be spelled the same, for example ''rose'' (flower) and ''rose'' (p ...
for 恋, another word that means "affection" or "love", so koi are symbols of love and friendship in Japan. Colored ornamental carp were originally called ''Irokoi'' (色鯉) meaning colored carp, ''Hanakoi'' (花鯉) meaning floral carp, and ''Moyōkoi'' (模様鯉) meaning patterned carp. There are various theories as to how these words came to be disused, in favor of ''Nishikigoi'' (錦鯉), which is used today One theory holds that, during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
, the words ''Irokoi'' and ''Hanakoi'' (which can have sexual meanings) were changed to ''Nishikigoi'' because they were not suitable for the social situation of war. Another theory is that'' Nishikigoi'', which was the original name for the popular Taishō Sanshoku variety, gradually became the term used for all ornamental koi.The History of Nishikigoi 錦鯉とその起源
Zen Nippon Airinkai


Taxonomy

In the past, koi were commonly believed to have been bred from the common carp (''Cyprinus carpio''). Extensive hybridization between different populations, coupled with widespread translocations, have muddled the historical
zoogeography Zoogeography is the branch of the science of biogeography that is concerned with geographic distribution (present and past) of animal species. As a multifaceted field of study, zoogeography incorporates methods of molecular biology, genetics, mor ...
of the common carp and its relatives. Traditionally, Amur carp (''C. rubrofuscus'') were considered a subspecies of the common carp, often under the scientific name ''C. carpio haematopterus''. However, they differ in
meristics Meristics is an area of ichthyology and herpetology which relates to counting quantitative features of fish and reptiles, such as the number of fins or scales. A meristic (countable trait) can be used to describe a particular species of fish, or us ...
from the common carp of Europe and Western Asia, leading recent authorities to recognize them as a separate species, ''C. rubrofuscus'' (''C. c. haematopterus'' being a junior synonym). Although one study of mitochondrial DNA (mtDNA) was unable to find a clear genetic structure matching the geographic populations (possibly because of translocation of carp from separate regions), others based on mtDNA, microsatellite DNA and
genomic DNA Genomic deoxyribonucleic acid (abbreviated as gDNA) is chromosomal DNA, in contrast to extra-chromosomal DNAs like plasmids. Most organisms have the same genomic DNA in every cell; however, only certain genes are active in each cell to allow for ...
found a clear separation between the European/West Asian population and the East Asian population, with koi belonging in the latter. Consequently, recent authorities have suggested that the ancestral species of the koi is ''C. rubrofuscus'' ( syn. ''C. c. haematopterus'') or at least an East Asian carp species instead of ''C. carpio''. Regardless, a taxonomic review of ''
Cyprinus ''Cyprinus'' is the genus of typical carps in family Cyprinidae. Most species in the genus are of East Asia origin with only the common carp (''C. carpio'') in Western Asia and Europe; this invasive species has also been introduced to many othe ...
'' carp from eastern and southeastern Asia may be necessary, as the genetic variations do not fully match the currently recognized species pattern, with one study of mtDNA suggesting that koi are close to the Southeast Asian carp, but not necessarily the Chinese.


Varieties

According to ''Zen Nippon Airinkai'', a group that leads the breeding and dissemination of koi in Japan, there are more than 100 varieties of koi created through breeding, and each variety is classified into 16 groups.The Varieties of Nishikigoi
Zen Nippon Airinkai
Koi varieties are distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, yellow, blue, and cream. Metallic shades of gold and platinum in the scales have also been developed through selective breeding. Although the possible colors are virtually limitless, breeders have identified and named a number of specific categories. The most notable category is , which is made up of the ''Kōhaku'', ''Taishō Sanshoku'', and ''Shōwa Sanshoku'' varieties. New koi varieties are still being actively developed. Ghost koi developed in the 1980s have become very popular in the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
; they are a
hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two dif ...
of wild carp and Ogon koi and are distinguished by their metallic scales.
Butterfly koi Butterfly koi, longfin koi, or dragon carp are a type of ornamental fish notable for their elongated finnage. The fish are a breed of the common carp, ''Cyprinus carpio'', which includes numerous wild carp races as well as domesticated koi ("Ni ...
(also known as longfin koi, or dragon carp), also developed in the 1980s, are notable for their long and flowing fins. They are hybrids of koi with Asian carp. Butterfly koi and ghost koi are considered by some to be not true ''nishikigoi''. The major named varieties include: * is a white-skinned koi, with large red markings on the top. The name means "red and white"; ''kōhaku'' was the one of the first ornamental variety to be established in Japan (late 19th century). * is very similar to the ''kōhaku'', except for the addition of small black markings called . This variety was first exhibited in 1914 by the koi breeder Gonzo Hiroi, during the reign of the Taishō Emperor. In the United States, the name is often abbreviated to just "Sanke". The ''kanji'', 三色, may be read as either ''sanshoku'' or as ''sanke'' (from its earlier name 三毛). * is a black koi with red (''hi'' 緋) and white (''shiroji'' 白地) markings. The first ''Shōwa Sanke'' was exhibited in 1927, during the reign of the Shōwa Emperor. In America, the name is often abbreviated to just "Shōwa". The amount of ''shiroji'' on ''Shōwa Sanke'' has increased in modern times (''Kindai Shōwa'' 近代昭和), to the point that it can be difficult to distinguish from ''Taishō Sanke''. The ''kanji'', 三色, may be read as either ''sanshoku'' or as ''sanke.'' * is a white-, red-, or yellow-skinned koi with black markings . The Japanese name means "tortoise shell", and is commonly written as 鼈甲. The white, red, and yellow varieties are called , and , respectively. It may be confused with the ''Utsuri''. * is a black koi with white, red, or yellow markings, in a
zebra Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: the Grévy's zebra (''Equus grevyi''), plains zebra (''E. quagga''), and the mountain zebra (''E. zebr ...
color pattern. The oldest attested form is the yellow form, called in the 19th century, but renamed by Elizaburo Hoshino, an early 20th-century koi breeder. The red and white versions are called and (piebald color morph), respectively. The word ''utsuri'' means to print (the black markings are reminiscent of ink stains). Genetically, it is the same as ''Shōwa'', but lacking either red pigment (''Shiro Utsuri'') or white pigment (''Hi Utsuri''/''Ki Utsuri''). * koi is light blue above and usually red below, but also occasionally pale yellow or cream, generally below the lateral line and on the cheeks. The Japanese name means pale greenish-blue,
spring onion Scallions (also known as spring onions or green onions) are vegetables derived from various species in the genus ''Allium''. Scallions generally have a milder taste than most onions and their close relatives include garlic, shallot, leek, chi ...
color, or
indigo Indigo is a deep color close to the color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine, based on the ancient dye of the same name. The word "indigo" comes from the Latin word ''indicum'', m ...
. * ' means "autumn green"; the ''Shūsui'' was created in 1910 by Yoshigoro Akiyama( 秋山 吉五郎, by crossing Japanese ''Asagi'' with German
mirror carp Mirror carp, regionally known as Israeli carp, are a type of domesticated fish commonly found in Europe but widely introduced or cultivated elsewhere. They are a variety of the common carp (''Cyprinus carpio'') developed through selective breedin ...
. The fish has no scales, except for a single line of large mirror scales dorsally, extending from head to tail. The most common type of ''Shūsui'' has a pale, sky-blue/gray color above the lateral line and red or orange (and very, very rarely bright yellow) below the lateral line and on the cheeks. * is a white fish with a ''Kōhaku''-style pattern with blue or black-edged scales only over the ''hi'' pattern. This variety first arose in the 1950s as a cross between a ''Kōhaku'' and an ''Asagi''. The most commonly encountered ''Koromo'' is an , which is colored like a ''Kōhaku'', except each of the scales within the red patches has a blue or black edge to it. Less common is the , which has a darker (burgundy) ''hi'' overlay that gives it the appearance of bunches of grapes. Very rarely seen is the , which is similar to ''Budō-Goromo'', but the ''hi'' pattern is such a dark burgundy that it appears nearly black. * is a "catch-all" term for koi that cannot be put into one of the other categories. This is a competition category, and many new varieties of koi compete in this one category. It is also known as . * is a dark koi with red (''Kōhaku'' style) ''hi'' pattern. The Japanese name means "five colors". It appears similar to an ''Asagi'', with little or no ''hi'' below the lateral line and a ''Kōhaku Hi'' pattern over reticulated (fishnet pattern) scales. The base color can range from nearly black to very pale, sky blue. * is a variety of which the whole body is one color and the body is shiny, and it is called differently depending on the color. * is a koi with colored markings over a metallic base or in two metallic colors. * is a cross between ''utsurimono'' series and ''Ōgon''. * is a koi with metallic (glittering, metal-flake-appearing) scales. The name translates into English as "gold and silver scales"; it is often abbreviated to ''Ginrin''. ''Ginrin'' versions of almost all other varieties of koi occur, and they are fashionable. Their sparkling, glittering scales contrast to the smooth, even, metallic skin and scales seen in the ''Ogon'' varieties. Recently, these characteristics have been combined to create the new ''ginrin Ogon'' varieties. * is any koi with a solitary red patch on its head. The fish may be a ''Tanchō Shōwa'', ''Tanchō Sanke'', or even ''Tanchō Goshiki''. It is named for the Japanese red-crowned crane (''Grus japonensis''), which also has a red spot on its head. * , "tea-colored", this koi can range in color from pale olive-drab green or brown to copper or bronze and more recently, darker, subdued orange shades. Famous for its docile, friendly personality and large size, it is considered a sign of good luck among koi keepers. * is a metallic koi of one color only (''hikarimono'' 光者). The most commonly encountered colors are gold, platinum, and orange. Cream specimens are very rare. ''Ogon'' compete in the ''Kawarimono'' category and the Japanese name means "gold". The variety was created by Sawata Aoki in 1946 from wild carp he caught in 1921. * ' (literally "nine tattooed dragons" is a black ''doitsu''-scaled fish with curling white markings. The patterns are thought to be reminiscent of Japanese ink paintings of dragons. They famously change color with the seasons. ''Kumonryu ''compete in the ''Kawarimono'' category. * is a light blue/gray koi with copper, bronze, or yellow (''Kohaku''-style) pattern, reminiscent of autumn leaves on water. The Japanese name means "fallen leaves". * ''Kikokuryū'' (輝黒竜, literally "sparkle" or "glitter black dragon") is a metallic-skinned version of the ''Kumonryu''. * ''Kin-Kikokuryū'' (金輝黒竜, literally "gold sparkle black dragon" or "gold glitter black dragon") is a metallic-skinned version of the ''Kumonryu'' with a ''Kōhaku''-style ''hi'' pattern developed by Mr. Seiki Igarashi of Ojiya City. At least six different genetic subvarieties of this general variety are seen. * Ghost koi ( 人面魚じんめんぎょ), a hybrid of ''Ogon'' and wild carp with metallic scales, is considered by some to be not ''nishikigoi''. *
Butterfly koi Butterfly koi, longfin koi, or dragon carp are a type of ornamental fish notable for their elongated finnage. The fish are a breed of the common carp, ''Cyprinus carpio'', which includes numerous wild carp races as well as domesticated koi ("Ni ...
( 鰭長錦鯉ひれながにしきごい) is a hybrid of koi and Asian carp with long flowing fins. Various colorations depend on the koi stock used to cross. It also is considered by some to not be ''nishikigoi''. * originated by crossbreeding numerous different established varieties with "scaleless"
German carp Mirror carp, regionally known as Israeli carp, are a type of domesticated fish commonly found in Europe but widely introduced or cultivated elsewhere. They are a variety of the common carp (''Cyprinus carpio'') developed through selective breedi ...
(generally, fish with only a single line of scales along each side of the dorsal fin). Also written as 独逸鯉, four main types of ''Doitsu'' scale patterns exist. The most common type (referred to above) has a row of scales beginning at the front of the dorsal fin and ending at the end of the dorsal fin (along both sides of the fin). The second type has a row of scales beginning where the head meets the shoulder and running the entire length of the fish (along both sides). The third type is the same as the second, with the addition of a line of (often quite large) scales running along the lateral line (along the side) of the fish, also referred to as "mirror koi". The fourth (and rarest) type is referred to as "armor koi" and is completely (or nearly) covered with very large scales that resemble plates of armor. It also is called ''Kagami-goi'' (鏡鯉、カガミゴイ), or mirror carp (ミラーカープ). File:Kohaku.jpg, Kōhaku File:Tanchosanke.JPG, Tanchō Sanke File:Showa4.JPG, Shōwa Sanke File:Koi asagi.jpg, Asagi File:AZBG_Koi.jpg, Bekko File:Gin Rin Showa.jpg, Gin Rin Shōwa


Differences from goldfish

Goldfish The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the wild have bec ...
(''Carassius auratus'') were developed in China more than a thousand years ago by
selectively breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant mal ...
colored varieties; by the
Song dynasty The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the rest ...
(960–1279), yellow, orange, white, and red-and-white colorations had been developed. Goldfish were introduced to Japan in the 16th century and to Europe in the 17th century. On the other hand, most ornamental koi breeds currently distributed worldwide originate from Amur carp (''Cyprinus rubrofuscus'') bred in Japan in the first half of the 19th century. Koi are domesticated Amur carp that are selected or culled for color; they are not a different species, and will revert to the original coloration within a few generations if allowed to breed freely. Some goldfish varieties, such as the
common goldfish The common goldfish is a breed of goldfish with no other differences from its living ancestor, other than its color and shape. Goldfish are a form of domesticated wild carp and are a close relative of koi. Most varieties of fancy goldfish we ...
,
comet goldfish The comet or comet-tailed goldfish is a single-tailed goldfish bred in the United States. It is similar to the common goldfish, except slightly smaller and slimmer, and is mainly distinguished by its long deeply forked tail. Comet goldfish tend ...
, and
shubunkin are a hardy, single-tailed goldfish with nacreous scales and a pattern known as calico. The Shubunkins are of Japanese origin.Chris Andrews, Interpet Publishing (2002) ''An Interpet Guide to Fancy Goldfish''. Erik L. Johnson, D.V.M. and Richard E ...
, have body shapes and coloration that are similar to koi, and can be difficult to tell apart from koi when immature. Goldfish and koi can interbreed; however, as they were developed from different species of carp, their offspring are sterile.


Health, maintenance, and longevity

The Amur carp is a hardy fish, and koi retain that durability. Koi are coldwater fish, but benefit from being kept in the range, and do not react well to long, cold, winter temperatures; their immune systems are very weak below 10 °C. Koi ponds usually have a metre or more of depth in areas of the world that become warm during the summer, whereas in areas that have harsher winters, ponds generally have a minimum of . Specific pond construction has been evolved by koi keepers intent on raising show-quality koi. The bright colors of koi put them at a severe disadvantage against predators; a white-skinned ''Kōhaku'' is a visual dinner bell against the dark green of a pond. Herons,
kingfisher Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly colored birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species found in the tropical regions of Africa, Asia, and Oceania, ...
s, otters,
raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight of ...
s, skunk, mink,
cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s,
fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelve sp ...
es, and
badgers Badgers are short-legged omnivores in the family Mustelidae (which also includes the otters, wolverines, martens, minks, polecats, weasels, and ferrets). Badgers are a polyphyletic rather than a natural taxonomic grouping, being united by the ...
are all capable of emptying a pond of its fish. A well-designed outdoor pond has areas too deep for herons to stand, overhangs high enough above the water that mammals cannot reach in, and shade trees overhead to block the view of aerial passers-by. It may prove necessary to string nets or wires above the surface. A pond usually includes a pump and filtration system to keep the water clear. Koi are an omnivorous fish. They eat a wide variety of foods, including peas, lettuce, and watermelon. Koi food is designed not only to be nutritionally balanced, but also to float so as to encourage them to come to the surface. When they are eating, koi can be checked for parasites and ulcers. Naturally, koi are bottom feeders with a mouth configuration adapted for that. Some koi have a tendency to eat mostly from the bottom, so food producers create a mixed sinking and floating combination food. Koi recognize the persons feeding them and gather around them at feeding times. They can be trained to take food from one's hand. In the winter, their digestive systems slow nearly to a halt, and they eat very little, perhaps no more than nibbles of algae from the bottom. Feeding is not recommended when the water temperature drops below . Care should be taken by hobbyists that proper oxygenation, pH stabilization, and off-gassing occur over the winter in small ponds, so they do not perish. Their appetites do not come back until the water becomes warm in the spring. Koi have been reported to achieve ages of 100–200 years. One famous scarlet koi named " Hanako" was owned by several individuals, the last of whom was Komei Koshihara. In July 1974, a study of the
growth rings Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
of one of the koi's scales reported that Hanako was 226 years old. Some sources give an accepted age for the species at little more than 50 years.


Disease

Koi are very hardy. With proper care, they resist many of the parasites that affect more sensitive tropical fish species, such as '' Trichodina,
Epistylis ''Epistylis'' is a genus of peritrich ciliate The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter an ...
'', and ''
Ichthyophthirius multifiliis ''Ichthyophthirius multifiliis'', often termed "Ich", is a parasitic ciliate described by the French parasitologist Fouquet in 1876. Only one species is found in the genus which also gave name to the family. The name literally translates as "the ...
'' infections. Water pH is important for maintaining koi's health. Water changes help reduce the risk of diseases and keep koi from being stressed. Two of the biggest health concerns among koi breeders are the
koi herpes virus ''Cyprinid herpesvirus 3'' (also CyHV-3, koi herpes virus or KHV) is a species of virus causing a viral disease that is very contagious to the common carp ''Cyprinus carpio''. Pathology It is most commonly found in ornamental koi, which are of ...
(KHV) and
rhabdovirus ''Rhabdoviridae'' is a family of negative-strand RNA viruses in the order '' Mononegavirales''. Vertebrates (including mammals and humans), invertebrates, plants, fungi and protozoans serve as natural hosts. Diseases associated with member vir ...
carpio, which causes
spring viraemia of carp Spring viraemia of carp, also known as swim bladder inflammation, is caused by ''Carp sprivivirus'', also called ''Rhabdovirus carpio''. It is listed as a notifiable disease under the World Organisation for Animal Health. Impacted species Sprin ...
(SVC). No treatment is known for either disease. Some koi farms in Israel use the KV3 vaccine, developed by Prof. M. Kotler from the Hebrew University of Jerusalem and produced by Kovax, to immunise fish against KHV. Israel is currently the only country in the world to vaccinate koi against the KHV. The vaccine is injected into the fish when they are under one year old, and is accentuated by using an
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
light. The vaccine has a 90% success rate and when immunized, the fish cannot succumb to a KHV outbreak and neither can the immunised koi pass KHV onto other fish in a pond. Only
biosecurity Biosecurity refers to measures aimed at preventing the introduction and/or spread of harmful organisms (e.g. viruses, bacteria, etc.) to animals and plants in order to minimize the risk of transmission of infectious disease. In agriculture, thes ...
measures such as prompt detection, isolation, and
disinfection A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than st ...
of tanks and equipment can prevent the spread of the disease and limit the loss of fish stock. In 2002, spring viraemia struck an ornamental koi farm in
Kernersville, North Carolina Kernersville is a town in Forsyth County and the largest suburb of Winston-Salem. The town is located in the U.S. state of North Carolina. A small portion of the town is also in Guilford County. The population was 26,481 at the 2020 census, u ...
, and required complete depopulation of the ponds and a lengthy quarantine period. For a while after this, some koi farmers in neighboring states stopped importing fish for fear of infecting their own stocks.


Breeding

When koi naturally breed on their own they tend to spawn in the spring and summer seasons. The male will start following the female, swimming right behind her and nudging her. After the female koi releases her eggs they sink to the bottom of the pond and stay there. A sticky outer shell around the egg helps keep it in place so it does not float around. Although the female can produce many spawns, many of the fry do not survive due to being eaten by others. On average if the egg survives around 4–7 days the fry will be hatched from the egg. Like most fish, koi reproduce through spawning in which a female lays a vast number of eggs and one or more males fertilize them. Nurturing the resulting offspring (referred to as "fry") is a tricky and tedious job, usually done only by professionals. Although a koi breeder may carefully select the parents they wish based on their desired characteristics, the resulting fry nonetheless exhibit a wide range of color and quality. Koi produce thousands of offspring from a single spawning. However, unlike cattle, purebred dogs, or more relevantly, goldfish, the large majority of these offspring, even from the best champion-grade koi, are not acceptable as ''nishikigoi'' (they have no interesting colors) or may even be genetically defective. These unacceptable offspring are culled at various stages of development based on the breeder's expert eye and closely guarded trade techniques. Culled fry are usually destroyed or used as feeder fish (mostly used for feeding
arowana Arowanas are freshwater bony fish of the subfamily Osteoglossinae, also known as bony tongues (the latter name is now often reserved for Arapaiminae). In this family of fish, the head is bony and the elongated body is covered by large, heavy sc ...
due to the belief that it will enhance its color), while older culls, within their first year between 3 and 6 inches long (also called ''tosai''), are often sold as lower-grade, pond-quality koi. The semi-randomized result of the koi's reproductive process has both advantages and disadvantages for the breeder. While it requires diligent oversight to narrow down the favorable result that the breeder wants, it also makes possible the development of new varieties of koi within relatively few generations.


In the wild

Koi have been accidentally or deliberately released into the wild in every continent except
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
. They quickly revert to the natural coloration of an Amur carp within a few generations. In many areas, they are considered an invasive species and a pest. In the states of
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and
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in Australia, they are considered noxious fish. Koi greatly increase the
turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids ...
of the water because they are constantly stirring up the substrate. This makes waterways unattractive, reduces the abundance of aquatic plants, and can render the water unsuitable for swimming or drinking, even by livestock. In some countries, koi have caused so much damage to waterways that vast amounts of money and effort have been spent trying to eradicate them, largely unsuccessfully. In many areas of North America, koi are introduced into the artificial "
water hazard A hazard is an area of a golf course in the sport of golf which provides a difficult obstacle, which may be of two types: (1) water hazards such as lakes and rivers; and (2) man-made hazards such as bunkers. The governing body for the game of ...
s" and ponds on golf courses to keep water-borne insect larvae under control through predation.


In common culture

In Japan, the koi is a symbol of luck, prosperity, and good fortune, and also of perseverance in the face of adversity. Ornamental koi are symbolic of Japanese culture and are closely associated with the country's national identity. In Chinese culture, the koi represents fame, family harmony, and wealth. It is a feng shui favorite, symbolizing abundance as well as perseverance and strength, and has a mythical potential to transform into a dragon. Since the late 20th century, the keeping of koi in outdoor water gardens has become popular among the more affluent Chinese. Koi ponds are found in Chinese communities around the world, and the number of people who keep koi imported from Niigata, has been increasing. In addition, there are increasing numbers of Japanese koi bred in China that are sold domestically and exported to foreign countries.
The reason why wealthy Chinese started to buy a lot of Japanese "nishikigoi" 1/3
', Gendai Business. 29 March 2019.

The reason why wealthy Chinese started to buy a lot of Japanese "nishikigoi" 3/3
', Gendai Business. 29 March 2019.
Koi are also popular in many countries in the equatorial region, where outdoor water gardens are popular. In Sri Lanka, interior courtyards most often have one or several fish ponds dedicated to koi.


See also

*
Culture of Japan The culture of Japan has changed greatly over the millennia, from the country's prehistoric Jōmon period, to its contemporary modern culture, which absorbs influences from Asia and other regions of the world. Historical overview The ances ...
*
Japanese aesthetics Japanese aesthetics comprise a set of ancient ideals that include '' wabi'' (transient and stark beauty), '' sabi'' (the beauty of natural patina and aging), and ''yūgen'' (profound grace and subtlety). These ideals, and others, underpin much of ...
*
Japanese white crucian carp The Japanese white crucian carp, also known as Japanese carp, white crucian carp, or gengoro-buna (''Carassius cuvieri''), is a species of freshwater fish in the carp family (family Cyprinidae). It is found in Japan and, as an introduced species, ...


References


History of Koi Fish


Further reading

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External links


Feature article on treating sick fish, especially koi, "Surgery to Scale," ''Cosmos Magazine''

Koi in the NIWA Atlas
{{Authority control Carp Fish of Japan Articles containing video clips