Key Points and Methods of Koi Breeding Techniques Explained

Because koi are large in size, they are generally bred in ponds. Koi eggs are sticky, and the fertilized eggs adhere to aquatic plants and other attachments to develop, so artificial spawning nests must be placed in the pond where koi are bred. To increase output, artificial breeding can be carried out to raise fry.

Sex identification in koi is relatively easy. By body shape, a fish with a plump belly is female, and one with a slender body is male; by the vent, the female's vent is broad and flat, while the male's vent is small and sunken inward. At the stage of sexual maturity, it can be checked by whether there are "nuptial tubercles" on the fin rays at the edge of the pectoral fins. Stroke the fin rays with your hand: if they feel rough with keratinous protrusions, the fish is male; if smooth, it is female. A mature male will release white milt when its belly is gently pressed.

For artificial breeding, select broodstock that have distinct breed characteristics, good color, markings, base color and posture, are healthy and lively, and have females that are large and plump. Broodstock for breeding can be used at a ratio of 1 female to 2 males to increase the fertilization rate. Although 1-year-old koi are already mature, to ensure quality it is best to choose 3-5-year-old broodstock. If the broodstock are too old, the hatching rate of the fertilized eggs will decrease. Before breeding, first keep the females and males separately, then put them back into the spawning pond at breeding time. The spawning pond can be an earthen pond or a cement pond, preferably with an area of about 20 sq m, and a water depth of about 1 m is suitable, depending on conditions. Disinfect the spawning pond 3 days before spawning. One day before spawning, put in the spawning nests. At a water temperature above 18°C, koi can spawn and fertilize naturally. After spawning, take out the spawning nests, disinfect them, and put them into the hatching pond.

A two-injection pectoral fin method can also be used for artificial induction of spawning. The dose for females is 12μg of luteinizing hormone-releasing hormone analogue per kg, and the dose for males is halved. The first injection is 1/3 of the total dose, and the second injection is the remaining amount, with an interval of 8 hours between the two injections. After injection, place the broodstock in the spawning pond and hang a row of spawning nests in the pond. After about 10 hours, eggs can be found at the opening of the spawning nests; immediately pull a net and use artificial insemination. One person holds a bowl or basin, and another holds the female fish and squeezes the eggs into the bowl or basin. Quickly squeeze out the milt and pour it into the bowl or basin containing the eggs. If there is too little milt, an appropriate amount of physiological saline can be added, stir with a feather for 1 minute, and evenly sprinkle it onto the net cloth containing the spawning nests in the cage. During hatching, use clean, pollution-free water with sufficient dissolved oxygen and a pH of 7-8. During hatching, mainly prevent water mold, generally by sprinkling 15-20ppm malachite green solution into the cage every day. Fry rearing: in the fry pond, culture rotifers as the opening feed for the fry, feed artificial feed after 1 week, and feed only artificial feed after 1 month.