1 Water conditions
A semi-circular breeding pond with a diameter of 180 cm and a maximum depth of 54 cm, made of glass-fiber reinforced plastic, was punched in the middle and inserted into a 30.40 cm PVC pipe. The nozzle is tied with 20-40 mesh nylon sieve to control the water level and prevent the fish from escaping. Three days before stocking fry, 30mg/L potassium permanganate solution was used to soak the rearing pond for 2 hours, then rinsed with fresh water, and then injected with fresh water. The water level was 30-40 cm, and remained fluid. Dissolved oxygen in the water is maintained at 7-8 mg/L, pH 7-7.5.
2 seed sources
Seedlings were directly hatched from the fertilized eggs. The fish were 10-11 mm in length and stocked at 5000-6000 per square meter. A total of 38 breeding ponds are counted as 200,000.
3 Feeding management
3.1 Water Quality Management Feeding water is deep well water. The well is first pumped into the reservoir and introduced into the rearing tank through the PVC pipe. In order to increase dissolved oxygen, block it with a wooden board at the well water outlet to allow it to fully aerate. After the water enters the rearing tank, it is blown with a blower to increase oxygen. The flow rate in the rearing tank is kept within 4,000 m/h. The water temperature is maintained at 22°C-23°C.
3.2 The baiting fry was just placed in the rearing tank and the yolk sac was larger and still in the endogenous trophic stage without feeding. After bred for 6.7 days, the body length of the fry reached 21-22 mm, and the yolk sac basically disappeared. At this time, a small amount of artificial granule bait could be fed, and 1 g per 4000 fry was fed on the first day and gradually increased to the next day. Feed 1 g per 1500 to 2,000 fry, and after the third day, feed 1 g of bait per 800 to 1000 feeds and feed 1 to 2 hours. At the same time, according to the size of the fish, adjust the size of feed pellets Feeding should be stopped for half an hour when feeding the bait: In the early period, feed is not fed, no discharge is required, only a certain amount of water flow is maintained, and the sieve can be washed regularly. Every 4.6 hours after the start of feeding, sewage should be discharged once. law.
3.3 Drug Prevention During the early larval rearing process, fry is easily dying within 5 to 6 days after the feed is fed. In this stage, malachite green, indoxacillin and furazolid must be used to prevent fish disease. .
4 Cultivation results
After 15 days of cultivation, the body length of the fry reached 34.5-38.5 mm, and the body weight was 167-206.5 mg. The survival rate was 83%.
5 results analysis
In the transition period between exogenous nutrition and endogenous nutrition, the acacia bark began to transition from 5 to 6 days after hatching. During this period, fry could easily die. The cause of death was as follows: First, the fry started to adapt to artificially formulated pellet diets. process. Few fry, especially those distributed on the surface of the water, will die because they do not feed or feed less than the feed is hunger. Secondly, due to the accumulation of bait, water mold will grow in the bait, causing the bait to flocculate in the bottom of the water. Once mistaken into it, it will suffocate death. Observation of the newly hatched fry found that there was bleeding in the cracks, spasms, and intestines, but the fry did not show signs of hydromycosis. Therefore, adopting appropriate measures to lower the water level, increase the feeding density, and remove the dirt from the screening screen in a timely manner are effective ways to increase the survival rate of the fry during this period.
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