Carp

The term carp (pl.: carp) is a generic common name for numerous species of freshwater fish from the family Cyprinidae, a very large clade of ray-finned fish mostly native to Eurasia. While carp are prized quarries and are valued (even commercially cultivated) as both food and ornamental fish in many parts of the Old World, they are considered trash fish and invasive pests in many parts of Africa, Australia and most of the United States.
The cypriniformes (family Cyprinidae) are traditionally grouped with the Characiformes, Siluriformes, and Gymnotiformes to create the superorder Ostariophysi, since these groups share some common features. These features include being found predominantly in fresh water and possessing Weberian ossicles, an anatomical structure derived from the first five anterior-most vertebrae, and their corresponding ribs and neural crests.
The third anterior-most pair of ribs is in contact with the extension of the labyrinth and the posterior with the swim bladder. The function is poorly understood, but this structure is presumed to take part in the transmission of vibrations from the swim bladder to the labyrinth and in the perception of sound, which would explain why the Ostariophysi have such a great capacity for hearing.
Most cypriniformes have scales and teeth on the inferior pharyngeal bones which may be modified in relation to the diet. Tribolodon is the only cyprinid genus which tolerates salt water. Several species move into brackish water but return to fresh water to spawn. All of the other cypriniformes live in continental waters and have a wide geographical range. Some consider all cyprinid fishes carp, and the family Cyprinidae itself is often known as the carp family.
In colloquial use, carp usually refers only to several larger cyprinid species such as Cyprinus carpio (common carp), Carassius carassius (crucian carp), Ctenopharyngodon idella (grass carp), Hypophthalmichthys molitrix (silver carp), and Hypophthalmichthys nobilis (bighead carp). Common carp are native to both Eastern Europe and Western Asia, so they are sometimes called a "Eurasian" carp.
Carp have long been an important food fish to humans. Several species such as the various goldfish (Carassius auratus) breeds and the domesticated common carp variety known as koi (Cyprinus rubrofuscus var. "koi") have been popular ornamental fishes. As a result, carp have been introduced to various locations, though with mixed results. Several species of carp are considered invasive species in the United States, and, worldwide, large sums of money are spent on carp control.
At least some species of carp are able to survive for months with practically no oxygen (for example under ice or in stagnant, scummy water) by metabolizing glycogen to form lactic acid which is then converted into ethanol and carbon dioxide. The ethanol diffuses into the surrounding water through the gills.
In 1653 Izaak Walton wrote in The Compleat Angler, "The Carp is the queen of rivers; a stately, a good, and a very subtle fish; that was not at first bred, nor hath been long in England, but is now naturalised."
Carp are variable in terms of angling value.
Various species of carp have been domesticated and reared as food fish across Europe and Asia for thousands of years. These various species appear to have been domesticated independently, as the various domesticated carp species are native to different parts of Eurasia. Aquaculture has been pursued in China for at least 2,400 years. A tract by Fan Li in the fifth century BC details many of the ways carp were raised in ponds. The common carp (Cyprinus carpio) is originally from Central Europe. Several carp species (collectively known as Asian carp) were domesticated in East Asia. Carp that are originally from South Asia, for example catla (Gibelion catla), rohu (Labeo rohita) and mrigal (Cirrhinus cirrhosus), are known as Indian carp. Their hardiness and adaptability have allowed domesticated species to be propagated all around the world.
Although the carp was an important aquatic food item, as more fish species have become readily available for the table, the importance of carp culture in Western Europe has diminished. Demand has declined, partly due to the appearance of more desirable table fish such as trout and salmon through intensive farming, and environmental constraints. However, fish production in ponds is still a major form of aquaculture in Central and Eastern Europe, including the Russian Federation, where most of the production comes from low or intermediate-intensity ponds. In Asia, the farming of carp continues to surpass the total amount of farmed fish volume of intensively sea-farmed species, such as salmon and tuna.
Selective breeding programs for the common carp include improvement in growth, shape, and resistance to disease. Experiments carried out in the USSR used crossings of broodstocks to increase genetic diversity, and then selected the species for traits such as growth rate, exterior traits and viability, and/or adaptation to environmental conditions such as variations in temperature. Selected carp for fast growth and tolerance to cold, the Ropsha carp. The results showed a 30 to 77.4% improvement of cold tolerance, but did not provide any data for growth rate. An increase in growth rate was observed in the second generation in Vietnam, Moav and Wohlfarth (1976) showed positive results when selecting for slower growth for three generations compared to selecting for faster growth. Schaperclaus (1962) showed resistance to the dropsy disease wherein selected lines suffered low mortality (11.5%) compared to unselected (57%).
The major carp species used traditionally in Chinese aquaculture are the black, grass, silver and bighead carp. In the 1950s, the Pearl River Fishery Research Institute in China made a technological breakthrough in the induced breeding of these carps, which has resulted in a rapid expansion of freshwater aquaculture in China. In the late 1990s, scientists at the Chinese Academy of Fishery Sciences developed a new variant of the common carp called the Jian carp (Cyprinus carpio var. Jian). This fish grows rapidly and has a high feed conversion rate. Over 50% of the total aquaculture production of carp in China has now converted to Jian carp.
Carp, along with many of their cyprinid relatives, are popular ornamental aquarium and pond fish.
Ornamental goldfish were originally domesticated from their wild form, a dark greyish-brown carp native to Asia, but may have been influenced by Carassius carassius and Carassius gibelio. They were first bred for color in China over a thousand years ago. Due to selective breeding, goldfish have been developed into many distinct breeds, and are found in various colors, color patterns, forms and sizes far different from those of the original carp. Goldfish were kept as ornamental fish in China for thousands of years before being introduced to Japan in 1603, and to Europe in 1611.
Nishikigoi, better known simply as koi, are a domesticated varieties of common carp and Amur carp (Cyprinus rubrofuscus) that have been selectively bred for color. The common carp was introduced from China to Japan, where selective breeding in the 1820s in the Niigata region resulted in koi. In Japanese culture, koi are treated with affection, and seen as good luck. They are popular in other parts of the world as outdoor pond fish.
A long tradition of common carp exists in Chinese culture and literature. A popular lyric circulating as early as 2,000 years ago in the late Han period includes an anecdote which relates how a man far away from home sent back to his wife a pair of carp (Chinese: 鲤鱼; pinyin: Liyu), in which, when the wife opened the fish to cook, she found a silk strip that carried a love note of just two lines: "Eat well to keep fit, missing you and forget me not".
At the Yellow River at Henan (Chinese: 河南; pinyin: Hénán; Wade–Giles: Ho-nan) is a waterfall called the Dragon Gate. It is said that if certain carp called yulong can climb the cataract, they will transform into dragons. Every year in the third month of spring, they swim up from the sea and gather in vast numbers in the pool at the foot of the falls. It used to be said that only 71 could make the climb in any year. When the first succeeded, then the rains would begin to fall. This Dragon Gate was said to have been created after the flood by the god-emperor Yu, who split a mountain blocking the path of the Yellow River. It was so famous that throughout China was a common saying, "a student facing his examinations is like a carp attempting to leap the Dragon Gate."
Henan is not the only place where this happens. Many other waterfalls in China also have the name Dragon Gate and much the same is said about them. Other famous Dragon Gates are on the Wei River where it passes through the Lung Sheu Mountains and at Tsin in Shanxi Province.
The fish's jumping feature is set in such a proverbial idiom as "Liyu (Carp) jumps over the Dragon Gate (Chinese: 鲤跃龙门)," an idiom that conveys a vivid image symbolizing a sudden uplifting in one's social status, as when one ascends into the upper society or has found favor with the royal or a noble family, perhaps through marriage, but in particular through success in the imperial examination. It is therefore an idiom often used to encourage students or children to achieve success through hard work and perseverance. This symbolic image, as well as the image of the carp itself, has been one of the most popular themes in Chinese paintings, especially those of popular styles. The fish is usually colored in gold or pink, shimmering with an unmistakably auspicious tone.
The modern Japanese Koi fish are a brightly colored species of the Amur carp that have been bred by rice farmers in Japan since the early 19th century. This subspecies of carp plays a significant role in Japanese art, often being depicted as symbols of luck, strength, and tenacity. For this reason, Koi fish are also presented as gifts in Japanese culture as symbols of love, gratitude, and peace. Their bright colors and unique patterns present a high degree of eloquence to the Japanese people, thus creating a level of respect and appreciation for the Koi.
With Koi fish being at the forefront of a lot of Japanese art, it is common to find modern depictions of Koi in paintings, home art, murals, and even tattoos.
To many people, Koi fish strongly represent Samurai warriors, as they are able to be seen swimming upwards against a rivers current, symbolizing a Samurai's bravery. One typical saying is the phrase "koi no taki-nobori", translating to "Carp climbing the waterfalls", a phrase that is used to describe a persons strength and perseverance.