How to improve the survival rate of fry cultivation First, strict disinfection and adequate water injection to create a good ecological environment. To choose a quick disinfectant lime, both to achieve a better disinfection effect, but also can increase the water body calcium content, promote plankton breeding, increase the fish palatability feed.
In order to reduce the labor intensity, flushing can be used to disinfect the water. Although the amount of quicklime is high, it is simple and convenient, the labor intensity is low, the disinfection effect is good, and it is economical. The specific approach is: first drain the pool water, according to the amount of 300 meters per acre surface, piled at the inlet of the fish pond, with the water to melt quicklime, quicklime solution with the water spread to the whole pool, so as to play a role in disinfection. Generally, all the lime is melted, and when the water reaches 20 to 30, the sterilization process ends. After 2 to 3 days of disinfection, the water can be injected. The water level of the fry pool should not be too deep, and the depth of the fish pond should be 80 to 90 degrees.
The second is timely and appropriate fertilization, cultivating a wealth of palatability feeds. In the initial stage of fry cultivation, whether there are abundant palatability bait in the water is a key factor in determining the survival rate of fry. According to the author's experiment, when the number of algae, protozoa, and rotifers per liter of water is between 3.5 million and 4 million, juvenile fish can be fed and the survival rate is high.
It is difficult for fish farmers in general to determine the amount of food organisms in the water, but it can be judged by observing the color of water. The water quality is slightly green, with a transparency of around 30?, and the zooplankton occlusions and copepods are less. It is the best time for the fish ponds. The key is to have a good grasp of the time and quantity of fertilization. The time of fertilization depends on the temperature of the water and the period of entry of the fish into the pond. When water temperature is 20～22°C, fish will be fertilized 70～80 hours before entering the pool; 22～24°C will be fertilized 50～70 hours before entering the pool; 24°C will be fertilized three days before entering the pool. The best combination of organic fertilizer and inorganic fertilizer can meet the nutrients needed for biological propagation of food, reduce oxygen consumption, and maintain good water quality. The amount of fertilizer applied depends on the fat condition of the fish pond. Generally, 50 kg of organic fertilizer, 8 kg of ammonium bicarbonate, and 10 kg of superphosphate are suitable for each mu of water.
The third is to reasonably determine the fry stocking time and density, and improve the survival rate and breeding efficiency. The fry stocking time refers to the time for the fry to enter the pool. What is the highest survival rate of the fish into the pool after release of the fish fry? Tests have shown that the choice is better in the mixed nutrition period. At this time, the yolk nutrition in the fry body has not completely disappeared, the energy of life activities is guaranteed, and the swim is lively. After entering the pond, there are also rich food organisms for feeding, which can greatly improve the survival rate. Some fishermen believe that the extension of fry in the ring in the incubation period or in the stash box in the holding time, more older (old mouth) fry survival adaptability, survival rate will be increased accordingly. actually not. After entering the flat swimming period, the fry can not obtain food in time, relying on the yolk to provide energy for life activities, the yolk will soon be consumed up, and the chance of survival after entering the pool will be greatly reduced. Here, we must particularly remind fishermen and friends that they should not adopt the old seedling pond culture method. The stocking of old seedlings will reduce the survival rate.
After several years of experiments with different density survival rates, the authors found that survival rates and growth rates were high when the stocking density was between 450,000 and 500,000 tails per mu. Therefore, the author believes that 450,000-500,000 tails/mu are economically reasonable stocking densities.
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