Natural reproduction of koi

The selection of good parent fish is the key to the reproduction of koi. To adopt natural reproduction, we must first choose the parent fish that meet the standard. In the north, after spending the winter indoors, koi, formerly reserved as a species of fish, moved to outdoor fish ponds in mid-late March. At this time, parent fish should be further selected to obtain excellent offspring.

(1) the selection of parent fish for breeding should generally have the following: strong physique, bright and clear color, pure Lu system, obvious breed characteristics, clear color spot margin, no false edge, no defect, smooth and neat scales, steady swimming posture and intact fins.

(2) the method of distinguishing between female and male carp there is a difference in the morphology of female and male fish when koi reaches mature age. Generally speaking, the female fish's body is short and plump, the abdomen is dilated, the closer it is to labor, the more obvious the abdomen is enlarged, and the head is slightly suffocated narrow and longer; the male fish is longer and thinner, and the part is wide and short, and the forehead is slightly raised. The tip of the pectoral fin of the female fish is round, while the end of the chest carp of the male fish is slightly pointed, and the difference between the female fish and the male fish is more obvious in the reproductive season. There are several white rotten small protuberances on the first fin and Gill cover of the pectoral fin of the male fish, which is called "chasing the star". Chasing stars disappears after the reproductive season. The reproductive pore of male fish is small and concave, and milky semen is released by gently pressing with hands; the reproductive pore of female fish is slightly wide and flat, slightly protruding, and eggs are released by gently pressing the abdomen with hands; during the reproduction of koi, whether the number of male and female parent fish is appropriate or not, it has a great relationship with the fertilization rate of eggs. In order to ensure a sufficient number of sperm and improve the fertilization rate of eggs, the ratio of female to male is 1:3 (one vocal female and 3 males form a group or 1:2 or 2:3 is better. If the number of male fish is small, the method of matching male to female fish at 1:1 is also acceptable. (2) the gonad of 3-year-old female koi carp is just mature and its reproductive function is not exuberant, so the number of eggs is small, the eggs are rotten and the hatched larvae are easy to be stunted, so they are generally not selected as parent fish. Parent fish that breed at the right age. Females who are suitable for reproduction are generally at the age of 4mur10, while males are more than 5 years old at 3mur. such parent fish have strong physique, full gonads, strong motility of eggs and sperm, high fertilization rate and hatching rate, so it is most ideal to be used as parent fish.

(3) cement fish ponds are used as spawning ponds in the preparation of spawning ponds. It is more suitable for square ponds with an area of 4 m x 4 m or rectangular ponds with an area of 4 m x 5 m. Fish ponds should not be too large, too large for management, and too small to affect the spawning activities of parent fish. The water depth is 30-40cm. The water quality with sufficient oxygen content, clean water quality, high hydrogen ion concentration 39.81-63.09nmol/L (PH7.2-7.4) and low hardness is better.

(4) Fish nests are used to attach fish eggs. Prepare fish nests before spawning. Generally, it is better to make fish nest with foxtail algae, palm bark and willow fibrous root (to be boiled many times). Tie it into a small bundle and you can use it.

(e) spawning in the northern region, the season for brocade carp spawning from late April to mid-June, when the water temperature rises to 16 Mel 18 degrees Celsius, parent fish can be moved into the spawning pond, and when the water temperature rises to 20 degrees Celsius, a large number of eggs can be laid, and the time of spawning starts at about 4 am until 10:00 or noon. If the weather changes suddenly and the water temperature drops sharply, spawning will be interrupted. Generally, a brocade carp with 30-40cm length lays 20-400000 eggs, and some of them will reproduce the remaining eggs after spawning for about one month. Like the eggs of goldfish, the eggs are also fertilized in vitro and belong to sticky eggs. The size of the rotten egg varies according to the size and age of the mother. The mother is large and the egg diameter is also large. On the contrary, the egg is also small. The egg diameter is generally 2.1ml 2.6 mm. After the fertilized egg absorbs water, the egg diameter is larger than that of the unfertilized egg. The nests, which are already covered with attached eggs, are removed from the spawning pond and soaked in 50.7% salt solution for 5 minutes, or 1/10000 malachite green solution for 10 minutes for 15 minutes. Or 3ppm methyl blue solution for 15 minutes, disinfection, and then transferred to the incubator to hatch. The use of these drugs has a certain effect on the prevention of water mildew.

(6) the first step for hatching is to prepare a hatching pool, using a cement pool with an area of 3 meters x 3 meters and a water depth of 30cm. The water temperature of the incubation pond should be the same as that of the spawning pond. When the water temperature is lower than or higher than 5 degrees Celsius, the hatching rate will be reduced, and the further increase of the water temperature difference will make the eggs die. The length of the incubation period is related to the water temperature. When the water in the incubator is turbid at 20 degrees Celsius, the larvae can be hatched in about 4 days. The higher the water temperature is, the shorter the hatching time is. On the contrary, the incubation time is longer. Generally speaking, it is said that the larvae can be hatched in 5 days after 4 words when the water temperature is about 18 degrees Celsius; when the water temperature is about 22 degrees Celsius, the larvae can be hatched in 4 days; when the water temperature is 25 degrees Celsius, the larvae can be hatched in 3 days. The hatched larvae do not eat and do not move, relying on the nutrients in the yolk sac to maintain the energy needed for fish survival. The attached organs on the fish body are adsorbed on the fish nest. When the nutrients in the yolk sac are absorbed, the larvae begin to swim and look for food. At this time, they can start to feed. The kinds of food and the feeding method are the same as those of the goldfish larvae. In addition to the above methods, the running water hatching method can also be adopted, in which the flow velocity should be paid attention to, and the flow can be larger at the beginning. The nests attached to the fish eggs are moved into the hatching cages with small meshes placed in the running water, and the holding quantity in the running water is higher, which is beneficial to the hatching of the fish eggs. When the fish fry are hatched, the flow rate should be reduced, or they may be placed in still water cages to continue to develop. Otherwise, it will damage the larvae, or the physical strength of the water pump will be disadvantageous to the development because of the large swimming capacity of the larvae.