(a) Fish breeding
1. Water quality conditions Aquaculture spring water, water quality is clear, water temperature anniversary in 5 ~ 18 °C, pH 7.8, dissolved oxygen 14.4 mg / l.
2. At the beginning of feeding and management, feeding 4 times a day, the feed was crushed with rainbow trout hard pellet feed to sieve small particles with a diameter of 2 mm, fed with blisters once every 8 to 10 days, and supplemented with vitamins. After the silver cockroach grows to 20 grams, it is fed twice a day. When it grows to 50 grams, it is transferred to a large cement pond with a length of 2 meters and a width of 20 meters.
7 to 10 days to clean the fish pond 1 day, morning and evening patrol ponds, found that fish is not normal or dead fish, it is necessary to take timely sampling and take measures.
The silver frog hid the shade and sheltered it from the light. A 3 square meter sunshade was placed on the top of the fish pond with asbestos tiles for silver storks to inhabit. The silver cocoon grows quickly and its specification reaches more than 100 grams, and it enters the adult fish breeding stage. With reference to the feeding method of rainbow trout, feed 2 times a day and clean the pond regularly. Throughout the breeding period, focus on the prevention of fatty liver disease.
(B) broodstock cultivation in the early pre-fertility-based, feed formula accounted for more than 50% of fish meal, fat 4% to 6%, increase the amount of feed to make it rapidly increase in body weight, increase fertility. Feed twice a day, and the feed amount is generally 1.5% of the fish's body weight. In the later period, the proportion of fat and fish meal in the feed was reduced, the amount of feed was reduced, and astaxanthin (3 ‰) was added and the ratio of vitamin E was increased.
During the feeding period, especially in the first half of the year, attention should be paid to the prevention and treatment of fatty liver disease. The sick fish showed black body color, thin body, and bent back at the tail shank. The swimming ability is poor, and the abdomen often rots when rubbed against the bottom of the pool. Anal swelling, no food in the intestines, full of yellow mucus. Liver yellow, gallbladder edema, mortality rate reached 30%.
After the discovery of fatty liver disease, 120 mg of vitamin E and 0.5 g of choline chloride were added per kilogram of feed, and the amount of feed was appropriately reduced. Vitamin E and choline chloride have been added afterwards.
(III) Reproduction Technology
1. Maturity and characteristics of male and female identification: The lower jaw is slightly curved, and the end is hooked and upturned. The abdomen is relatively inflated and hard. The reproductive hole is small and not prominent. Female characteristics: The jaws are straight and the ends are not hooked. The abdomen is enlarged and soft. The reproductive hole is large, red, and prominent.
After being sexually matured, the silver frog is fed with astaxanthin, which is very dark and has a yellow belly.
2. Sex ratio Male and female fish are separately reared during hatching, and the male to female ratio is 1:1.
3. The body length of the 2 larvae of silver frog females is generally about 45 cm and the weight is 1.5-2 kg. The relative ovulation amount is 180-185 grams per kilogram of female body weight, and the average number of grains per gram of eggs is 7.4 grains, so the number of eggs per female kilogram is about 1300 grains. When artificially propagated, it can generally extrude 80%, and another 20% is left in the fish cavity.
4. Artificial Insemination and Incubation Mature male and female fish are placed in the cement tank in the hatchery at a ratio of 2:1. Insemination uses the dry-guide method: first squeeze the egg, squeeze the eggs of the 2 females into the perforated plastic basket at a time, wash the broken egg and urine with equal liquid, pour into the enamel pot, squeeze the semen and use the feather quickly Stir for 15 to 20 seconds. After the mixture of the semen and the egg is even, add a little of the liquid and stir for 30 seconds. Rinse the sperms, break the eggs, etc. with fresh water. After 1 hour, the dead eggs (white) were picked and poured into hatching trays to hatch. During hatching, keep the fish eggs quiet and shading. From the 4th day after hatching, sterilize 30 to 50 g/m3 methylene blue every 3 to 4 days for 1 hour to prevent saprophytic infection.
(4) Precautions Silver oysters only produce 1 egg for life. Shortly after reproduction, male and female fish will continue to die. Therefore, the breeding of silver coffins must be well planned. In the first year of cultured adult fish, the fish can be sold at the end of the first year when the fish reaches 500 grams. After breeding, the broodstock is sold or slaughtered to prevent loss.
Author: Gansu Provincial Fisheries Research Institute
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