Nursery process
1. Broodstock breeding
The water quality of the stingray broodstock culture pond should be kept clean and free from contamination; the dissolved oxygen in the pool water must be maintained at 3.5 mg/l, pH 6.5-8.5. In the period of 1 month to 2 months before the preparation for production, water should be flushed every 7 days to 10 days. The flushing time is 50 minutes to 80 minutes. When flushing, the water in the original pool can be used for flushing to form a stream in the pond to stimulate the development of gonads in the broodstock of the stingray.
2. Broodstock selection
It is generally required that there be more than 350 grams of males and 150 grams of females. When collecting, it should be noted that the male and female individuals of broodstock have large differences and are male and female. Males are large in size, with thin and thin abdomen and darker body. There is a sharp pointed urogenital mastoid behind the anus, which is about 0.6 cm to 0.8 cm long. Females are short and small, the abdomen is enlarged and soft, and the body color is slightly shallow. After the anus Without urogenital papillae, there is a round gonadal hole, followed by a small urinary hole. The collected broodstock requires vigorous and active body surface smooth without injury. The fish that have abnormal swimming and significant hooking and scraping on the surface must be removed. Otherwise, they will slowly die after entering the pool. Before lowering the pool, the broodstock should preferably be soaked in water for 4 minutes with a minimum of 4/100 salt and baking soda mixture before going down the pond to infect with watery mildew.
3 brood fish production
Huge broodstock in Huzhou, Zhejiang Province, is rarely used for artificial oxytocin and natural breeding. If artificial eggs are inseminated, the male to female ratio is 4:1. A variety of oxytocin injections are effective. The general dose is: females are injected with PG 1 mg-3 mg plus Domone (DOM) 1 mg-3 mg plus LRH-A 5 g-15 g/kg body weight. The male dose was 0.7 times that of the female. Two-needle injection, needle distance 10 hours -12 hours. Water temperature 24 °C -27 °C, effect time l5 hours -22 hours.
4. Use of oxytocin
Induced doses: PG (pituitary gland) 3 mg/kg - 6 mg/kg, HCG (chorionic hormone) 800 ppm/kg - 1200 ppm/kg, LRH-A (analog) 20 μg/kg - 30 μg/kg.
Effect time: The maturation of the fish has a certain relationship with the flow conditions, the maturity is fast, the flow conditions are fast, usually 24°C-28°C, and the effect time is 20 hours-25 hours.
5. Cultivate basic facilities
There is a reservoir outside the seedling plant that feeds the water needed for the nursery pool. The conditions of the reservoir are:
(1) An area of ​​4 mu - 5 mu, according to the needs of the nursery.
(2) Better water color, abundant planktonic microalgae and zooplankton, less harmful algae. Top dressing regularly, detoxification.
(3) The water inlet should be fully sterilized and the bottom quality is good.
The water pipe uses a PVC pipe to supply the water in the reservoir to the nursery pond and is internally diverted to each nursery pond. The gauze filter is needed at the end of the reservoir to ensure that the water entering the seedling pond is free of large dirt.
The water in the reservoir is fed into the nursery pool through the main pipeline and is regulated and diverted in the nursery pond. Ensure that water supply during the hatchery pool water supply stimulates hatching during the incubation process, and at the same time, ensure that the hatchery water source is clean. During the incubation process, the regulation of the incubation water flow should be carried out according to the situation. In the initial stage of hatching, the flow of water can be appropriately increased so that the fish eggs can be slightly wandered in the water. In the later stage of hatching, as the fry gradually hatches, the flow rate of water can be adjusted at this time to prevent the fry from swimming after the film is out of the membrane and consume the physical strength of the fry and reduce the survival rate of the fry.
In the hatchery, there is a drainage pipe opposite the water inlet pipe so that the water flow can be discharged to ensure the cleanliness of the water body and the water quality in the hatchery. There is a central drainage tank in each of the four cement hatching tanks to discharge water out of the culture tank.
Sturgeon fish eggs require higher dissolved oxygen during embryonic development, and the dissolved oxygen in the hatching water must be maintained at 5 mg/l. When the eggs of the sturgeon fish hatch, they require fresh water for incubating water, high dissolved oxygen, and no algae and excessive organic matter. Contaminated water cannot be used as hatching water.
Breeding key points
1. Treatment of broodstock ponds The area of ​​broodstock culturing pools is generally between 1 mu and 2 mu. The specific size can be determined according to the seed production scale, and the water depth of the culturing pool should be maintained at about 2.2 meters. Because the individual of the stingray broodstock is small, the area of ​​the nursery pond should not be too large. The area of ​​the cultivation pond is too large, and the miscarriage of the broodstock of the stingray is often caused by the delay of production.
The cultivation pool must be cleared once a year to clear the wild fish in the pond, kill predators and pathogens, and improve the water quality of the pond. If it is a pond, remove the mud from the bottom of the pond. As a breeding pond for stingray broodstock, whether it is a newly excavated pond or an old pond, the pond must be disinfected before the broodstock goes down the pond.
Pond clear pond disinfection more commonly used drugs lime, bleach.
Stocking density
The stocking density is 2000 tails/mu, and at the same time, 200-300 tails of white squid species ranging from 10 cm to 13 cm can be mixed per acre of ponds, and planktons in water can be ingested by the flower pupa to achieve water quality control. Stocking ratio Male: Female = 3:1.
3. Broodstock nutrition
In the broodstock incubation stage, due to the need of sexual maturity, the demand for nutrition of the stingray is relatively high. The natural feed of the pond alone is difficult to meet the needs of growth and gonadal development of the broodstock of the stingray, and the supplement of the foreign aid nutrition must be strengthened, that is, feeding artificial feed. In artificial feeds, protein should reach 33%-35% and fat should reach 7%. The protein content of fish meal in artificial diets is above 60%, fat content is 5%-10%, minerals are 15%-19%, and it is also rich in vitamin A and vitamin D, which can meet the nutritional requirements for broodstock growth and development.
4. Egg hatching
(1) Sturgeon fish eggs require high dissolved oxygen during hatching. The dissolved oxygen in hatching water should be kept at 5 mg/L; the pH value should be around 7.5; the incubation water temperature should be 18°C-28°C. The incubation temperature is 22°C-28°C.
(2) The water used for incubation must be filtered to prevent predators and contaminants from entering the hatchery and affect the hatching effect.
(3) In the incubation process, the regulation of the incubation water flow should be carried out according to the situation. In the initial stage of hatching, the flow of water can be appropriately increased so that the fish eggs can be slightly wandered in the water. In the later stage of hatching, as the fry gradually hatches, the flow rate of water can be adjusted at this time to prevent the fry from swimming after the film is out of the membrane and consume the physical strength of the fry and reduce the survival rate of the fry.
(4) The collection of fish eggs is collected using palm leaves. The palm leaves must be fully exposed before use to prevent the growth of mold and other diseases and affect the living rate of collecting eggs. Place the exposed, disinfected palm leaves in a rubber bucket for use.
Stingray has a habit of nesting and laying eggs. It puts a rubber bucket with palm leaves into the pond as a spawning nest for stingrays. The handle is tied with a string, and the string is floated on the other end and floats on the water. It is convenient to remove the barrel and observe the collection of fish eggs. Stingray broodstock will spawn in the barrel. Stingray eggs are settled eggs that will accumulate on palm leaves and replace them with new palm leaves when the eggs reach a certain amount.
The palm fronds enriched with eggs are hung in the wood bar and placed in the hatching pool. The density is arranged according to the size of the hatching pool to ensure sufficient space for the circulation of the water body. Observe the hatching of fish eggs regularly to prevent mildew.
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