Koi or more specifically nishikigoi are ornamental varieties of domesticated common carp (Cyprinus carpio) that are kept for decorative purposes in outdoor koi ponds or water gardens.
Koi varieties are distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, yellow, blue, and cream. The most popular category of koi is the Gosanke, which is made up of the Kohaku, Taisho Sanshoku, and Showa Sanshoku varieties.
Carp are a large group of fish originally found in Central Europe and Asia. Various carp species were originally domesticated in East Asia, where they were used as food fish. The ability of carp 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. Carp were first bred for color mutations in China more than a thousand years ago, where selective breeding of the Prussian carp (Carassius gibelio) led to the development of the goldfish.
The common carp was aquacultured as a food fish as at least as far back as the fifth century in China. The common carp was also known to have been aquacultured in Europe by the Roman Empire, which could have spanned a time period of 27 BC to 400 AD. Common carp were first bred for color in Japan in the 1820s, initially in the town of Ojiya in the Niigata prefecture on the northeastern coast of Honshu island. By the 20th century, a number of color patterns had been established, most notably the red-and-white Kohaku.
The outside world was not aware of the development of color variations in koi until 1914, when the Niigata koi were exhibited in the annual exposition in Tokyo. At that point, interest in koi exploded throughout Japan. The hobby of keeping koi eventually spread worldwide. They are now commonly sold in most pet stores, with higher-quality fish available from specialist dealers.
Extensive hybridization between different populations has muddled the historical zoogeography of the common carp. However, scientific consensus is that there are at least two subspecies of the common carp, one from Western Eurasia (Cyprinus carpio carpio) and another from East Asia (Cyprinus carpio haematopterus). One recent study on the mitochondrial DNA of various common carp indicate that koi are of the East Asian subspecies.
However, another recent study on the mitochondrial DNA of koi have found that koi are descended from multiple lineages of common carp from both Western Eurasian and East Asian varieties. This could be the result of koi being bred from a mix of East Asian and Western Eurasian carp varieties, or being bred exclusively from East Asian varieties and being subsequently hybridized with Western Eurasian varieties (the butterfly koi is one known product of such a cross). Which is true has not been resolved.
Koi varieties are distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, yellow, blue, and cream. While the possible colors are virtually limitless, breeders have identified and named a number of specific categories. The most popular category is Gosanke, which is made up of the Kohaku, Taisho Sanshoku, and Showa Sanshoku varieties.
New koi varieties are still being actively developed. Ghost koi developed in the 1980s have become very popular in the United Kingdom; they are a hybrid of wild carp and Ogon koi, and are distinguished by their metallic scales. Butterfly koi (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:
Kōhaku is a white-skinned koi, with large red markings on the top. The name means "red and white"; kohaku was the first ornamental variety to be established in Japan (late 19th century).
Taishō Sanshoku (or Taisho Sanke) is very similar to the kohaku, except for the addition of small black markings called sumi. This variety was first exhibited in 1914 by the koi breeder Gonzo Hiroi, during the reign of the Taisho Emperor.[citation needed] In America, the name is often abbreviated to just "Sanke".
Shōwa Sanshoku (or Showa Sankeis a black koi with red and white markings. The first Showa Sanke was exhibited in 1927, during the reign of the Showa Emperor. In America, the name is often abbreviated to just "Showa". The amount of shiroji on Showa Sanke has increased in modern times (Kindai Showa), to the point that it can be difficult to distinguish from Taisho Sanke.
Tanchō is any koi with a solitary red patch on its head. The fish may be a Tancho Showa, Tancho Sanke, or even Tancho Goshiki. It is named for the Japanese crane (Grus japonensis), which also has a red spot on its head.
Chagoi, "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.
Asagi 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 colour, or indigo.
Utsurimono is a black koi with a white, red, or yellow markings, in a zebra colour pattern. The oldest attested form is the yellow form, called "black and white markings" in the 19th century, but renamed Ki Utsuri by Elizaburo Hoshino, an early 20th-century koi breeder. The red and white versions are called Hi Utsuri and Shiro Utsuri, respectively. The word utsuri means to print (the black markings are reminiscent of ink stains). Genetically, it is the same as Showa, but lacking either red pigment (Shiro Utsuri) or white pigment.
Bekko is a white-, red-, or yellow-skinned koi with black markings sumi. The Japanese name means "tortoise shell". The white, red, and yellow varieties are called Shiro Bekko, Aka Bekko and Ki Bekko, respectively. It may be confused with the Utsuri.
Goshiki is a dark koi with red (Kohaku style) hi pattern. The Japanese name means "five colours". It appears similar to an Asagi, with little or no hi below the lateral line and a Kohaku Hi pattern over reticulated (fishnet pattern) scales. The base color can range from nearly black to very pale, sky blue.
Shūsui means "autumn green"; the Shūsui was created in 1910 by Yoshigoro Akiyama (by crossing Japanese Asagi with German mirror carp. 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 have 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.
Kinginrin 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. There are Ginrin versions of almost all other varieties of koi, and they are fashionable. Their sparkling, glittering scales contast 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.
Kawarimono 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 kawarigoi.
Ōgon is a metallic koi of one color only. 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. Recently, the metallic-skinned Ogon is being crossed with ginrin-scaled fish to create the ginrin Ogon with metallic skin and sparkling (metal flake) scales.
Kumonryū 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 colour with the seasons.[citation needed] Kumonryu compete in the Kawarimono category.
Ochiba 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".
Koromo is a white fish with a Kohaku-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 Kohaku and an Asagi.[citation needed] The most commonly encountered Koromo is an Ai Goromo, which is coloured like a Kohaku, except each of the scales within the red patches has a blue or black edge to it. Less common is the Budo-Goromo, which has a darker (burgundy) hi overlay that gives it the appearance of bunches of grapes. Very rarely seen is the Tsumi-Goromo which is similar to Budo-Goromo, but the hi pattern is such a dark burgundy that it appears nearly black.
Hikari-moyomono is a koi with coloured markings over a metallic base or in two metallic colours.
Kikokuryū（literally "sparkle" or "glitter black dragon"）is a metallic-skinned version of the Kumonryu.
Kin-Kikokuryū （literally "gold sparkle black dragon" or "gold glitter black dragon"）is a metallic-skinned version of the Kumonryu with a Kohaku-style hi pattern developed by Mr. Seiki Igarashi of Ojiya City. There are (at least) six different genetic subvarieties of this general variety.
Ghost koi, a hybrid of Ogon and wild carp with metallic scales, is considered by some to be not nishikigoi.
Butterfly koi 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.
Doitsu-goi originated by crossbreeding numerous different established varieties with "scaleless" German carp (generally, fish with only a single line of scales along each side of the dorsal fin). There are four main types of Doitsu scale patterns.
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 are completely (or nearly) covered with very large scales that resemble plates of armor. They also are called Kagami-goi, or mirror carp.
