The breeding of koi can be achieved through artificial intervention, and there are mainly two methods: artificial egg extrusion and artificial promotion of natural ovulation.
In the method of artificial egg extrusion, first of all, it is necessary to determine whether the koi has entered the breeding period. Usually, between April and May each year, small white granular protrusions will appear on the pectoral fin rays at the base and on the gill covers of male fish. These are called "nuptial tubercles", which are the signs indicating that male fish have entered the breeding period. After selecting the male and female parent fish, the female fish is scooped out and its abdomen is pressed manually to extrude the eggs. Then, the eggs are mixed with the sperm of the male fish and placed in the prepared fish nests for hatching.
Another method is the artificial promotion of natural ovulation. The selected parent fish are put into separate clear water pools or cages, and fish nests are hung on the water surface to allow the koi to spawn naturally. If there are a large number of parent fish, this method can be chosen because it is closer to the process of natural breeding.
During the breeding period, it is very important to keep the water quality clean and maintain a suitable water temperature. This helps to improve the success rate of breeding. In addition, selecting parent fish that are physically strong and of pure breeds can improve the quality of the offspring.