Megalobrama amblycephla yih, commonly known as Wuchang fish, was originally found in Liangzi Lake, Hubei Province. It is a high-quality freshwater aquaculture and herbivorous fish in China. It mainly eats a variety of plants in natural waters, and also prefers to eat ryegrass under artificial breeding conditions. , Sudan grass, Mexican corn, alfalfa and other forage grass, and herbivorous livestock have similarities. The food chain is short, the energy conversion efficiency is high, the growth is rapid, the disease is small, the meat is delicious, and the economic value is high.
At present, on the breeding of C. breviscapus, many production units have no control, the reproductive effect is not ideal, and the phenomena of absent production and obstructed labor are common. The relevant technologies are summarized below.
1. The general biological basis of the head lice breeding group is the first sexual maturation age of 2 instars, 3-6 years of age is appropriate, and the 7th instar broodstock's reproductive capacity begins to decline. 1 year of sexual cycle, spawning time concentrated in the water temperature of 20-26 Â°C in the middle and late May, is the best time for reproduction, about half a month earlier than the eel and carp. Propagation requires fish nests and microfluidic conditions. There can be no spawning of eggs and microfluidic waters. The average annual egg production is 8-100000 eggs/kg body weight.
1.1 Male and female identification (see Table 1)
1.2 Ovarian maturation coefficient of the sexual cycle females was the lowest from October to February of the following year, rising from March to March, reaching 22% in May as the highest peak, falling from June to July, and sometimes reaching 14% in August. At the second peak, there was a significant decrease thereafter; male sperm testes had the lowest maturation coefficient from September to December, with an average of less than 1%, and rose from January to March. The peak reached 5.8% in May and gradually declined afterwards. Table 1 Comparison of male and female sex characteristics of C. cephalophorus Male fins of pectoral fins of males are thicker, slightly sharper, and wavy and curved. The first fins are thin and slightly curved (this character is present at age 1). At the time of sexual maturity, the back of the first few fins of the pectoral fins, only a small number of "stars" on the eyelids and back of the body during sexual maturity. The fins of the tail and the pelvic fins have dense "stars". Touching them with a rough feeling is relatively small. When sexually mature, lightly pressurizes the testis, and the large, soft, vent holes protrude slightly. Sometimes ruddy milky white semen flows out.
1.3 The biology of mature eggs Oocytes rely on follicular membranes and numerous microvessels to supply nutrients in the ovary. After the eggs mature, the follicular membrane ruptures and the eggs are released from the ovary fluid in the ovary. This is the reproductive physiology of the fish. ovulation". The fertilized egg has a shorter time of fertilization. When the water temperature is 25Â°C, the fertilizing ability is sometimes more than 1 hour. If eggs that mature after ovulation cannot be produced in time, the eggs will â€œdeadâ€ due to insufficient nutrition and become over-cooked and lose fertility.
2. Preparation before reproduction
2.1 Parents' parents choose as many different geographic locations as possible to avoid degradation of inbreeding traits.
2.2 The ratio of male to female is approximately 1:1.5, and artificial insemination can be 1:1.
2.3 The parental weight requirement is above 1kg.
2.4 It is appropriate to choose the age of the parent.
2.5 To strengthen postpartum cultivation and spring feeding, using refined materials and green materials to promote the recovery and development of gonads, began to gradually reduce food intake around 5 days before reproduction, and stop eating the day before induction.
2.6 The choice of maturity
2.6.1 Mature female fish The abdomen enlarges, the outline of the ovary is obvious, the touch is soft and elastic, and the reproductive hole is slightly ruddy. In order to accurately identify the degree of maturity, an oviduct can be used to retrieve the eggs.
2.6.2 Mature female pectoral fins The first fins have obvious bead on the back of the first ray. The hand touches the surface of the body and the caudal stalk has a rough sense. In particular, there is a milky thick semen flowing from the abdomen to the abdomen. it is good.
2.7 Preparation of spawning ponds, fish nests, and hatchery equipment The spawning pool borrows four spawning spawning ponds with a diameter of 8m and a height of 1.6m. 12-20 old plastic nets of size 80X80cm are used as fish nests. If hatching in ponds, poplar roots, palm hulls and aquatic grasses are used as fish nests. The hatchery equipment borrows the hatching tanks of the four individual fishes, etc. If the pond is hatched, no hatchery equipment is needed.
3, oxytocin technology
3.1 Oxygen production drugs and effective doses HCG or PG alone can induce spawning and have a good effect. LRH-A alone does not normally lay eggs. For females, one injection and two injections can be used.
One-needle injection method:
The gonadal development generally uses a needle injection method, if the gonadal development is good, low doses can be used;
Two-needle injection method:
The first needle is usually used with the 1/10 dose of the above-mentioned one-needle injection method or only LRH-A 4 Î¼g/kg, which is called â€œpremature needleâ€; the interval is 5-10 h (due to the degree of maturity, the water temperature varies) The second needle was injected, and the drug and dose were the same as the above-mentioned one-needle injection method. Two-needle injection method was used for slightly worse gonadal development.
For males, injections are only given at the time of the last injection of the female, and the dose is half that of the female.
3.2 The effect time is closely related to the degree of gonad maturation, hormone potency, and water temperature (see Table 2).
Table 2 Relationship between water temperature and effect time Water temperature (Â°C) Effect time (h) 18-19 12 20-21 10 22-23 9 24-25 8-7 26-27 12 6
4. Spawning and hatching Spawning and hatching The stimulation of microfluidic water is started 1.5 hours before spawning. When the broodstock is in estrus, the females are in the front, and the males chase after the females and continue to rub the abdomen of the female fish. This behavior occurs in the broodstock. Predicting that eggs will be laid soon.
4.1 (grant) fine
4.1.1 Natural Insemination and Spawning As soon as the females have just laid their eggs, the males are immediately discharged to complete the fertilization process. Fertilized eggs are poorly viscous, and their viscosity increases around 1 h. If the old mesh is used as a fish nest, most of the eggs will enter the collection pool along with the flowing water and should be collected in time to prevent the eggs from suffocating due to lack of oxygen. . The collected eggs can be directly placed in the hatchery to be flow-incubated without de-bonding, and the eggs on the mesh and spawning ponds should also be eluted in time for hatching. The eggs have a large specific gravity and have a certain viscosity. The speed of flow should be slightly greater than the hatching flow rate of the four major fishes; if poplar roots, palm hulls, etc. are used as fish nests for pond hatching, egg collection and elution of eggs are not required. Egg-laying broodstock should also be separated from the eggs in time to prevent the broodstock from swallowing fish eggs.
4.4.2 Artificial insemination Avoiding exposure of fish eggs to water, the fertilizing ability of the eggs is particularly quickly lost when they enter the water. Into the water for 10s, the fertilization rate is only 38.5%, and the 40s fertility is basically lost. Therefore, the use of dry insemination is good, and the specific operation of artificial insemination with cockroaches and squid. Detackify the formulation with 1 kg of fine clay, 5 kg of water, and 25 g of salt. Descale and incubate in an enlarged incubation vessel.
4.2 Incubation requirements Dissolved oxygen is not less than 4mg/L, PH value is 7 to 8.5, and is filtered through 80 mesh vinyl fiber cloth to prevent sword water.
4.2.1 Incubation of nested eggs with pond nests Choose a sheltered shelter from the sun in the south to the south of the north and clear the ponds in advance. Hang the nests of eggs with eggs at 30cm below the water surface, and hung 40 to 500,000 fish eggs per acre. . 20 ~ 25 Â°C 44h fish out of the film; 25 ~ 27 Â°C about 38h film, fish out of the film after 3 ~ 4d can remove the nest, the emergence rate is generally about 20%.
4.2.2 Flowing water incubates 60 to 1 million grains/m2. Oxygen consumption of the embryo of the head maggot was gradually increased with the development stage, and the oxygen consumption of the embryonic body rotation stage, the film-out stage and the seedling stage increased significantly in the gastro-intestinal stage, muscle effect stage. Pay attention to the control of the water flow rate. Generally, the water flow can be larger when it enters the hatching tank, and then it can be gradually reduced to a slight turning of the water surface. After the film is opened, the water flow can be appropriately increased to float the seedlings; Pay attention to scrub screens, especially when emerging; kill enemies in the water, use 90% crystals of trichlorfon 0.5ppm, stop the flow 3~5min; control of fish eggs hydropodium, 2ppm malachite green 1~2 times, each Stop the water for 5~10min and stir the water continuously to prevent hypoxia. The fertilization rate was counted after hatching about 36.5 hours in the middle of the original midgut; the emergence rate was counted 2 days after the release of the fry or when the seedlings were sold.
5. Summary In summary, it is recommended that artificial oxytocin production, natural fertilization, and flowing water incubation be recommended. Its main advantages are as follows.
5.1 greatly increased the utilization rate per unit of water surface Incubation of 5 million fish eggs in the pond requires fish ponds 6.667~8.004hm2, while only 5 to 6 hatching tanks are used for hatching with running water.
5.2 Production Concentration Ponds Incubation is required to clear the pond 10-15 days before the urine production. The workload is large, and it takes about 25 days before and after the production of a batch of fry, which takes more time. Flowing water hatching requires only one manpower, and the entire production only takes 7 to 8 days.
5.3 Significant increase in the rate of emergence of the seedlings. After hatching, the small ponds with a length of 2m and a width of 1.5m are often dragged slowly along the edge of the pond after the â€œspill pointâ€ is hatched. The paste is easily affixed to the net and the discharge rate is only 20%~30. %. While the flow of water is hatched, more than 90% of the seedlings after the â€œwaist pointâ€ can be sold or sold, with almost no mechanical damage.
5.4 Fish nests Instead of poplar roots, palm nets and other waste nets are used as fish nests, which are solid and free from impurities, and have a clean hatching environment, save time and labor, and are easy to control the occurrence of watery mildew.
5.5 Induction rate, fertilization rate, and emergence rate are all higher than 80%.
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