Koi carp or ornamental carp is a fish belonging to one of the ornamental varieties of the common carp (Cyprinus carpio carpio Linnaeus, 17581). Now prized worldwide, the development of ornamental carp originally appeared in China, Korea, Japan and Vietnam.
This freshwater fish was obtained from crosses between selected individuals of the common carp (Cyprinus carpio) which originally lived in ponds used as reservoirs for rice fields. Essentially vegetarian, this carp is not a predator despite its large size. These fishes have various colors: red, white, yellow, black, etc.
Some colored varieties are highly prized by collectors and fetch huge prices while still only about two years old. In Southeast Asia, Koi are considered a symbol of love and virility.
The Japanese term "koi" (鯉, koi?) simply means carp. Ornamental carp are called nishiki-goi (錦鯉?, literally "brocade carp") in Japan, a word derived from their Chinese name jinli (simplified Chinese: 锦鲤; traditional Chinese: 錦鯉; pinyin: jǐn lǐ).
Koi carps are omnivorous with a herbivorous tendency and therefore of a peaceful and gregarious character. Grouped in schools, they go back and forth together between their resting and feeding places.
Koi prefer sandy or muddy bottoms where they search for food with their two pairs of barbels. The higher the water temperature, the more voracious the carp will be.
When the temperature drops below 6 °C, the carp practically stop feeding and enter a phase of semi-hibernation (also called lethargy) which can last all winter. They hide at the bottom of the pond, almost buried in the mud, to protect themselves from the cold.
Carp are known for their longevity, usually 18 to 20 years, but some specimens have reached 70 years.
Koi carp can only be kept outdoors in landscaped basins or ponds. They are unable to survive in an aquarium as it takes 5 cubic meters of water for an adult carp.
The Koi carp is a large fish once it reaches adulthood, it requires special attention on the filtration of its pond. The more koi there are, the bigger the biological filtration should be. Depending on the type of mechanical filtration and the performance of the biological filter, a volume of 5 to 10% of the pond should be dedicated to biological purification.
Installing a biological filter adapted to Koi carp, calibrated according to the final population and an efficient mechanical filtration are essential factors to maintain adult Koi carp in captivity.
Koi carp is a peaceful and familiar animal, so cohabitation with other fish species is not a problem.
Koi are content with any type of pond food. The amount taken in depends on the water temperature, so the food is easier to dose if it floats. During the winter months and below about 6-8 °C, it is not necessary to feed them.
This fish is known for its docility. With gentleness and a little patience, Koi will feed in your hand and are easily touched.
Koi carp is not native to Japan. The oldest form of nishikigoi, called magoi, was black and lived in the Black, Caspian, Aral and Azov seas. It is in China that the first writings about them appear around 500 BC. Koi carp was introduced in Japan during the Chinese invasions.
The first breeding techniques of this carp were also invented in China essentially for the taste of its flesh. Chromatic variations were then limited to red and grey.
In the seventeenth century, in the Niigata region, carp was introduced into rice fields to improve the rice diet of the farmers. The first remarkable chromatic mutations appeared between 1804 and 1830 and concerned red, white and yellow carps.
Between 1830 and 1850, kohaku were created as a result of a cross between white and red carp. By the end of the 19th century, most of the current varieties were established.
However, the breeding of koi carp was not successful beyond the borders of Niigata. However, some fish were soon worth their weight in gold and breeding was temporarily banned by the local authorities who considered it as speculation.
The koi were brought out of their isolation at an exhibition in Tokyo in 1914, when the mayor of a village in Niigata sent 27 of them to raise awareness of the harsh working conditions in the region. Eight of these carps were given to the son of Emperor Taisho as a gift and this was an event that led to the spread of koi carp all over the world.
The market for Koi carp has expanded considerably after World War II due to air transport and the establishment of farms outside Japan. Many countries are now producing ornamental carp, but the quality of Koi raised in Japan surpasses the competition.
Koi can be very expensive, depending on their class: A, B and C (class A being the most expensive). The price of some rare and very aesthetic specimens could reach 200,000 dollars (180,000 euros) in the early 2000s. A sale in 2018 reached the record amount of $1,800,000.
Class A Koi carp come only from Japanese farms and are considered to be the best. Koi carp born from Japanese parents but not bred in Japan form the B grade. On the other hand, grade C carps are not related to Koi and should not be considered as such.
The most popular Koi carp is the tancho. This carp is white with a single red spot on the top of the head, particularly popular with the Japanese because of the pattern reminiscent of the country's flag. The name comes from the Japanese crane, which also has this pattern.
The koi carp is considered a domestic animal under French law.
Koi carp is represented by different varieties:
Brocade carp have an important place in Japanese culture, where they are a symbol of love and virility. Their success has spread everywhere these fish have been exported, they bring a lot of charm and dynamism to a garden pond. Koi are very calm and bring beauty and serenity to a pond.
In Japan, these carps were used to decorate the gardens. They gave a touch of color, life and serenity in this place of rest. Traditionally, the prestigious guest would choose the specimen he would eat during the meal.
More specifically, they represent strength and perseverance, as they swim up the rivers and waterfalls of Japan and Asia against the current. According to the Chinese legend, the carps of the Yellow River, after having gone up the river, would fly to the sky by transforming themselves into dragons. This legend is said to be the origin in Japan of koi-nobori (鯉幟?, lit. "carp banner"), koi-shaped windsocks used on Children's Day, May 5, inherited from the Chinese festival of duanwu, the 5th day of the 5th month of the lunar calendar), once intended to encourage boys to be strong and valiant.
In Chinese culture, the koi carp has eight virtues. It shows through them the Way to live always in tune with reality.
It is said that the philosopher Confucius received a koi carp from the king and named his son after this fish, because he was the only one who could go up the falls of the Yellow River.
In China, they adorn the basins of Buddhist and Taoist temples, usually alongside carnivorous turtles, thus creating a natural balance, or parks and gardens.
In the same way, in Europe, black carps are often placed in the basins of castles.
The entrance to the scabbard (saya) of a sword (katana) is called koiguchi (鯉口?), lit. "carp mouth".
The Pokémon Magicarpe and its evolution Leviator are inspired by the legend of the Yellow River Waterfall (see the legend of the koinobori).