Experiment on early rearing of eel seedlings in greenhouse

At present, the cage culture of eel is concentrated in July, the survival rate is high and the risk of culture is low. However, the concentrated acquisition of Miaoyuan is less, the price is high, and the weight gain multiple is low. If the eel seedlings are purchased early and the temperature is unstable, the mortality rate of eel seedlings is high. How to solve this problem? We have carried out the experiment of early rearing of eel seedlings in greenhouse, and the results are summarized as follows:

I. Test conditions

1. Test pool: the newly excavated water surface is 250m long, 4m wide, 1.5m deep and covers an area of 1000 square meters. The source of water is lake water, and there are intake and drainage facilities.

two。 Cage: made of polyethylene nodular-free mesh with a mesh of 20 mesh. Cage specifications: 3 meters long, 1 meters wide, 1 meter high, a total of 40 test boxes. Insert the cage on March 2, put water peanuts in the box on March 3, and build a plastic greenhouse on March 4 to make the water plants grow early.

II. Test situation

1. Stocking: in late March, the box was full of water plants. On April 10th, eel seedlings were collected from the same day caught by nearby farmers. They were purchased in sunny days and operated with water. The seedlings were harvested 30,100kg per day until May 11th. A total of 1200 kg seedlings were collected, including 10 boxes for 3 times and the rest for 2 times. The size of eel seedlings is 20g / tail, 5kg per square meter. There is no need for drug disinfection before leaving the box, and the next day it began to sprinkle germicidal red for two consecutive days to disinfect the water, eel seedlings and aquatic plants with a concentration of 0.3 mg / L.

two。 Domestication: eel seedlings in the afternoon, began to feed fresh surimi, a box of water peanuts to make three tables, surimi on the table, the same day you can hear the sound of eating. It was fed only once a day at 5 p.m., starting at 1% of the body weight of the eel, gradually increasing to 5%, and surimi throughout the domestication period.

3. Change water: at the beginning, the water quality in the shed is relatively stable, the water is changed once every 7 days, the temperature rises in the second half of the month, and once every 2-3 days. The method is to choose to discharge 30%-50% old water in the morning on a sunny day, and add fresh water at noon.

4. Temperature regulation: the air temperature in the greenhouse changed greatly, but the water temperature did not change much, and the temperature difference between day and night was about 3 ℃. The water temperature in the greenhouse was 2: 3 ℃ higher than that outside the shed at night, and eel seedlings ate normally in rainy days. After April 20, the sunshade net is added outside the greenhouse, and in May, both sides of the greenhouse will be ventilated during the day and covered at night.

5. Disease prevention: water quality detoxification protective agent is sprinkled in the box once a month, germicidal red is spilled again, and no eel disease occurs.

III. Test results

1. The domestication time of eel seedlings in the box depends on the eating situation and weather of eel seedlings. If the food intake is more than 5% for more than 7 days, there is continuous fine weather, and the water temperature can be stable more than 20 ℃, the eel seedlings can be moved into large open-air box culture. We began to move eel seedlings out of the greenhouse on April 26, and ended on May 18. A total of 1152 kilograms of eel seedlings were removed from the greenhouse, with a survival rate of 96%. The weight gain of eel seedlings was not obvious.

two。 The cost of domestication in greenhouse is 1900 yuan in net cage, greenhouse and agricultural film, 1200 kg × 15 yuan in eel seedlings, 2700 yuan in fresh miscellaneous fish, 2700 yuan in medicine and 100 yuan in electricity, with a total cost of 22900 yuan. Calculated according to 1152 kg of eel seedlings coming out of the shed, it is 19.87 yuan per kg, which is much cheaper than that of 24 yuan per kg collected in July. What is more important is that the growth period is 2-3 months ahead of schedule, the multiple of weight gain and the benefit of culture are much better.

IV. Summary

1. The main factor affecting the survival rate of eel seedlings in greenhouse is the quality of eel seedlings. In the experiment, we strictly grasp the purchase methods of eel seedlings: the first is to choose sunny weather; the second is to purchase nearby; the third is to operate with water to ensure that the ratio of seedlings to water is more than 1 ∶ 2; the fourth is to control the receipt and release within 4 hours and only collect the same day's seedlings; fifth, the seedlings collected should be strictly selected and abnormal seedlings such as injured and floating heads should be resolutely eliminated. In this way, the survival rate in the box is high, and only two or three seedlings die in a box of 15kg. If the seedlings are not harvested well, the mortality rate is also very high.

two。 The water temperature in the greenhouse is high, and the water quality is easy to deteriorate. The setting density of the cage and the planting density in the box should not be too large. We think that the area of the cage should not exceed 50% of the total water surface, and the planting density should be 3-4 kg / m2.

3. The change of water in the greenhouse must be carried out on a sunny day, drain in the morning, and add water when the water temperature outside the shed rises at noon to prevent the temperature difference from being too large.