Detailed Explanation of Koi Breeding Techniques: Key Methods Every Farmer Must Know

1. Selecting parent fish; For koi breeding as ornamental fish, parent fish must be selected purposefully. Koi are mainly viewed from the back, so it is best to choose those that are relatively flat top to bottom, with a flat oval cross-section and an overall spindle shape, while the color should be chosen according to the breeding purpose by selecting parent fish with the corresponding body color.

2. Preparing the spawning pond; As a spawning pond, a small cement pond is generally used. The shape of the pond is not limited, with a scale of 4 m high, 4 m wide and 0.8 m deep, and a water depth of 0.4 to 0.5 m. Water for breeding is best with a pH of 7.2-7.4, slightly brackish and low hardness, and the dissolved oxygen in the water body should be guaranteed to be above 4 mg/L. Pay attention to disinfecting the pond and preparing the spawning nests in advance and putting them into the pond early; the spawning nests are generally made of hornwort or palm bark that has been boiled and soaked, tied into small bundles.

3. Spawning; In the northern regions of our country, late April to mid-June is the breeding season for koi. When the water temperature rises to 16-18°C, the selected parent fish can be moved into the spawning pond. Each pond only needs 2-3 groups of parent fish. After the parent fish enter the pond, when they are found to chase each other urgently, it indicates that spawning is about to begin. Spawning generally starts at around 4 o'clock in the early morning and ends at around 10 in the morning. Generally, 200,000-400,000 eggs can be produced at one time. The egg diameter of koi is generally 2.1 to 2.6 mm. After being laid, they absorb water and expand, the egg membrane protrudes outward, and their stickiness causes them to adhere to the spawning nest for hatching. After the parent fish finish spawning, take out the spawning nest with fertilized eggs, soak it in 5%-7% salt water for 5 minutes for disinfection, then move out the new fish and carry out hatching in the spawning pond.

4. Hatching; The water depth during hatching is generally 30 cm, and the water quality and water temperature requirements are the same as those for spawning water.; The length of hatching time is directly related to water temperature, and within the suitable water temperature range it shortens as the water temperature rises. At a water temperature of about 18°C it takes 4-5 days, at 20°C-22°C it takes 3-4 days, and at 25°C it takes about 3 days. Newly hatched fry do not move or eat, and rely on absorbing the yolk sac in the abdomen for nutrition. After the yolk is completely absorbed, the fry begin to swim freely and start feeding on external food; at this time, bait should be fed in time.

5. Rearing of fry; The process of rearing fry is also a process of selecting the superior and eliminating the inferior, and is a process of multiple selection and cultivation. The selection process is generally carried out 3-4 times within 3 months after the fry hatch. First selection: carried out within 20-30 days after the fry hatch, starting when the fish body grows to about 3 cm. It mainly involves keeping individuals with a strong constitution, lively swimming and obvious breed characteristics, while eliminating other individuals or rearing them separately for sale. However, due to different varieties, their growth speed and the time for forming markings are also different. For example: Showa Sanshoku koi start selection about 15 days after hatching, Ogon-type koi start about 50 days after hatching, and Kohaku series and Taisho Sanshoku series koi start about 60 days after hatching. Second selection: starts about 20 days after the first selection. The selection criteria are the quality of the fin shape, whether the color is bright, whether the pattern markings are clear, whether the breed characteristics are obvious, and so on. The subsequent third and fourth selections are basically the same as the second selection.