The genetics of koi fish

The commitment of numerous generations of Japanese koi farmers has provided us the modern koi, with its more than 100 types and their distinctive color and pattern variations, some  more desired than others.

The intrinsic qualities of koi, as loved by keepers, breeders and enthusiasts, are governed by a intricate set of genetic and ecological elements.

Modern day koi breeders have broad access to scientific research. The study of genetics in general requires the study of visible characteristics in offspring. Applying conventional techniques, it typically takes 20 generations of devoted, well-planned, selective breeding to be able to establish qualities of preferred character in koi. Results have to be painstakingly recorded and that, unfortunately, is a tradition followed by very few, if any, conventional koi farmers.

Research of koi genetics have been slow, because koi take around two to three years to reach maturity. Carp can mature in a much shorter time, but koi breeders have got inadvertently slowed the rate at which fish achieve maturity even further by breeding for improved body confirmation in order to produce large, show-winning fish. They would never use a female developing gonad at the age of one year.

Recently, advancements in analytical techniques for genome investigation have speeded up genetic research. These techniques were applied into the genetic variability of the koi stock of Niigata’s Yamakoshi region, where a relatively high mortality rate at the larval period had been observed. Koi were obtained from all the significant breeders in the region and examined. The study found that not only was there a low genetic variability inside the Niigata population, but the genetic distance between Kohaku, Sanke and Showa was small, suggesting that these favored kinds originated from a small founding population.

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