Principles of Genetics and Breeding

14.1.4.The Domestication of Common carp

From China, the breeding of common carp spread all over the world. From Asia the rearing of the carp spread to Europe and later to America, Australia, and Africa. Even if the common carp had been domesticated independently in China much earlier than in Europe, the European domestic forms were later introduced to eastern Asia (Basavaraju et al ., 2003). Wild common carp from the Danube River is the most ancestral form that was initially kept as exploited captives and later domesticated.

An effective reproductive barrier appears to have been formed, resulting in two races of the common carp.

• In China, common carp has been grown for many centuries in polyculture ponds at high densities, whereas in Europe low density monoculture is practiced. The different methods of domestication resulted in two different breeds of common carp.
• Transition of common carp from exploited captives to truly domesticated animals took place in the 12th century. Sooner or later different forms of domestic common carp appeared in the various pond systems.
• When the wild common carp was introduced into a pond system it naturally started to change its torpedo-shaped body into a deep, laterally compressed and hunchbacked body.
• Soon individuals appeared that did not have regular, geometrical arrangement of scales but showed severe irregularities, scale reductions or even complete scalelessness. These variations soon became a foundation for artificial selection.
• Ultimately, domesticated common carp are represented by a variety of forms, such as scaled carp, line carp, mirror carp, and leather or nude carps.
• The domesticated common carp not only changed its external shape, scalation and colour, but also underwent internal and physiological changes.
• Domesticated common carp selected to utilize supplementary food, grew better in ponds when man-made food was added. Studies on the wild common carp in ponds proved that wild common carp progeny was better suited for stocking natural riverine habitats than were domesticated varieties.

Fig. 1. A wild common carp (a) and its feral form (b) from the Danube delta in 1900 (from Antipa, 1909).

• The intestine of the wild common carp was 15 to 25% shorter than that of a domesticated carp. Longer intestines in domesticated fish are probably due to utilization of vegetable food not normally consumed by wild common carp.
• Also, wild common carp has both chambers of the swim bladder of similar size, whereas the domesticated fish has the anterior chamber always much larger and the posterior chamber smaller; the proportion (%) is 61:39 for the wild and 90:10 for the domesticate. This may be related to the relative greater mass of the head in a domesticated common carp.
• Specific forms of the domesticated common carp are created and maintained through constant artificial selection in nearly every pond culture system.
• The emergence of koi

The emergence of koi – the most expensive fish in the world common carp was traditionally reared for human food in small terrace ponds alternating with rice paddies between Nagaoka and Ojiya cities near Tokyo, Japan.

The area is known to have one of the highest snowfalls in the world and the whole area is under at least 6 mt of snow for 6 months.

These unusual conditions may have contributed to the more frequent occurrence of colour aberrations in common carp cultured here. The high incidence of colour aberrations may be caused by melatonin production during the prolonged life in total darkness under the cover of deep snow.

Although coloured common carp is recorded from >70 years ago, commercial scale selection of true ‘nishikigoi’ (koi) probably started only in the 1950s.

Koi, as they are known today, are colour aberrations of Cyprinus carpio. They probably originated from domesticated common carp or its feral forms, and from some more recent imports from Europe (doitsu koi). When colour aberrations started to appear more frequently and demands for them increased, production and crossbreeding intensified and their progeny were severely culled, leaving only the best coloured individuals one out of 10,000 or more, for further breeding.

Today, the Japanese recognize 15 basic colour aberrants of the common carp that are called koi.

Each of these aberrants has many varieties.

• The standard is for the carp body to remain cylindrical and the colours to be viewed from above.
• Koi with elongated fins and scale or body deformation is not accepted in Japan but appears frequently from producers in Israel and elsewhere.
• After several cullings only the most promising and appealing colours are retained and from these grow numerous beautiful ‘nishikigoi’.
• In Japan the favourites are red and white koi, red, black and white and a black koi with white and red imposed.