A case study on the loss of Shrimp Culture

In order to sum up the experiences and lessons of crayfish culture, the author recently investigated more than 20 households in Tangkou of shrimp culture in the urban area. According to the survey, 80% of shrimp farmers made profits in 2011, with an average profit of 750 yuan per mu, with the highest reaching 1050 yuan. But nearly 20% of farmers lost money, and those with the highest losses almost lost all their money. In this paper, the reasons for the loss of shrimp culture are summarized and analyzed, and the relevant countermeasures are put forward for reference.

First, reasons

1. Clearing the pond is not complete. Zhou in Yuhuanggang Village of embroidery Office has been farmed continuously for 4 years, and the silt at the bottom of the pond is more than 0.5m thick. every year, shrimp seedlings are simply disinfected with drugs such as quicklime or strong chlorine. as a result, the feeding of shrimp seedlings is abnormal and the growth is slow. The reason is that the toxic and harmful substances such as ammonia nitrogen and nitrite seriously exceed the standard. Although sediment modifiers and related biological agents are often used for regulation, the pathogen lurks in the bottom silt, shrimp diseases occur frequently in culture, and the effect of repeated drug use is not good, resulting in losses under adult shrimp specifications, low yield and high cost.

2. The condition of the pond is poor. In Xiuban Lujiapu village, Yang raised shrimp without finishing the soil pit pond on the highway, the ability of water conservation and flood control on the ridge was poor, the bottom of the pond was uneven, and the source of water was not ideal. Shrimp seedlings encountered amorous feelings shortly after stocking, and some of the ridges were flooded with water. Although they were urgently blocked with nets, they were mixed with wild miscellaneous fish and shrimp. After the wind period, they could not be cleared. Wild mixed fish, shrimp and crayfish competed for food, oxygen and air. You don't get what you deserve for your investment.

3. The origin of seedling is not authentic. A farmer, listening to the rhetoric of illegal shrimp seedling traders, bought shrimp seedlings from a non-standard seedling farm, although the price of shrimp seedlings was about 20 yuan lower than that of the local seedling farm. As a result, shrimp seedlings were not quarantined and brought in the virus. When shrimp grew to 2-3cm, shrimp began to die, resulting in an outbreak of shrimp disease in shrimp ponds, and drug treatment was of no use. Later, it was learned that the seedling vendors were shrimp fry poured from an epidemic area, and the loss outweighed the gain.

4. The quality of feed is poor. Some shrimp farmers unilaterally in order to save costs, choose low-cost low-quality feed, the nutritional composition is not comprehensive, the proportion is not scientific, resulting in malnutrition, seriously affecting the formation of shrimp seedlings.

5. Disease control is not standard. Some farmers did not carry out feeding and management in accordance with the operating rules, and were not standardized in pond cleaning, disinfection, bait, water quality management and disease prevention, resulting in continuous disease of shrimp during culture, and emergency medical treatment after the occurrence of diseased shrimps, which generally existed the phenomenon of drug abuse and misuse of drugs, which not only could not cure the disease of shrimp, but also caused the deterioration of water quality and drug residues.

II. Countermeasures

1. Strictly clean the pond and disinfect it. Every year, shrimp ponds should drain water, remove silt, eradicate weeds, repair pond ridges, and arrange into and drain the water system. The shrimp pond should be exposed to the sun for 15-20 days until the surface of the pond is dry and cracked. Two weeks before planting, a small amount of water was injected, the bottom of the pond was evenly scattered after melting with 100kg quicklime per mu, and the bottom was raked once in the silt by artificial method, and the whole bottom was covered with water every few days, sprinkled in the whole pool with 2kg chlorine dioxide and soaked 50kg rapeseed cake per mu, 2-3 days later, the disinfection water was released, the pool was sunburned for 3-5 days, and then filtered and injected with new water.

2. Improve the conditions of culture. The basic conditions such as environment, area, water depth and water quality index should meet the GB/T18407.4 standard. The water source does not have any pollution, the water quantity is sufficient, the water quality conforms to the NY5051 standard, the intake and drainage is convenient. The shrimp pond is rectangular, broad and sunny, with a flat bottom, sandy soil or loam. During the shrimp growth period, the pH value of shrimp pond water quality should be controlled in the range of 7.58.5, ammonia nitrogen below 0.1mg/L, nitrite below 0.1mg/L, dissolved oxygen above 5mg/L, bottom H2S not more than 0.1mg/L, organic matter content not more than 5mg/L, transparency between 25 and 35cm.

3. Choose and buy high-quality shrimp seedlings. Before selecting and purchasing shrimp seedlings, it is necessary to investigate the production license, credibility and parent shrimp sources of the seedling farm, the cultivation of shrimp seedlings sold over the years, the use of drugs during the breeding period, and so on. Shrimp seedlings should be tested by the inspection and quarantine department before leaving the scene, and do not enter the seedlings from the epidemic area to prevent pathogens from entering. It is best to release high-quality shrimp seedlings from the same seedling farm in the same area, and do not release other shrimp seedlings that have not been tested.

4. Strengthen the management of water quality. Properly replenish water and fertilize during the culture period, maintain a certain degree of fertility of the water quality, adjust the composition of algae in the water, make green algae or diatoms become the dominant population, and open to a certain number. The indexes such as dissolved oxygen, ammonia nitrogen, nitrite and PH value are measured every 7-10 days. If a certain index is uncomfortable, relevant measures should be taken in time. After one month of stocking, the shrimp seedlings should use the microbial preparation once every 10-15 days to remove the harmful substances in the pond; after two months of culture, attention should be paid to improving the substrate, such as using the substrate modifier, turning on the aerator to increase oxygen, and so on.

5. Choose and feed. Select large-scale, stable quality, palatable nutritious feed varieties to meet the nutritional needs of each growth stage. Enhance the immune function of shrimp, resist the invasion of pathogens and environmental mutation. Feeding should insist on eating more and less, and assist to feed live bait 1-2 times a week (small miscellaneous fish, snails, clams, clams, etc.). And often periodically add immune polysaccharides, shrimp multi-dimensional, etc., to enhance disease resistance and anti-allergy ability.

6. Scientific prevention and treatment of diseases. Crayfish disease prevention and control should be transformed into various aspects of prevention, management and health care. During the culture period, we should adhere to the morning and evening pond inspection, observe the occurrence of shrimp disease, but also understand the occurrence of shrimp disease near and around the culture area, and take relevant measures in time to find problems. During the growth period, every 15-20 days, use bromochlorohydantoin spray disinfection in the whole pool, can also be disinfected with quicklime, but the dosage and frequency should not be too much. The drug use in shrimp ponds strictly complies with NY5001 and NY5007 standards.