Main meteorological disasters and countermeasures of river crab culture
The growth, activity, feeding and molting of river crabs are closely related to meteorological conditions and disasters.In the management process of crab breeding, it is necessary to pay close attention to the weather forecast and early warning, and take preventive measures in advance, so as to achieve the purpose of high survival rate, large specifications, good quality and high yield of crab species.Based on years of experience in crab culture and grass-roots guidance, the author summarized the main meteorological disasters and preventive measures in crab culture as follows for the reference of the majority of farmers.1. Low temperature freezing injury mainly occurs at the early stage of crab species stocking. Low temperature can cause young crabs to not eat or eat less, which is extremely unfavorable to the early growth of young crabs, resulting in delayed molting stage and increased mortality, which is the main factor affecting the survival rate of young crabs.Preventive measures: analyze the weather forecast of early spring and the weather law over the years, all preparations should be made to prevent low temperature cold wave before crab planting, avoid low temperature period of crab planting, confirm that the temperature reaches above 5℃ for several days, and then put crab planting into deep water.When the temperature plummets after the weather warms up (commonly known as “inverted cold”), the crab pool water level can be deepened at this time to keep warm and stop feeding.When the weather turns fine and the temperature returns to normal, the water level of crab pool can be lowered to about 50cm to promote the temperature rise of crab pool and make crabs start eating as soon as possible.In the early spring, when the crab is planted, it is necessary to treat the crab with suitable temperature and water. After the crab is raised, abnormal loss is found. It is necessary to fill the seedlings in time.Second, continuous rain mainly occurs in two periods: first, continuous low temperature rain in early spring leads to low pond temperature and low food intake of juvenile crabs, which seriously affects the first molting of crabs and leads to low survival rate.Second, the plum rain season continuous rain.The lack of dissolved oxygen in the pond, and the growth of aquatic plants is in the flourishing period, the respiration is enhanced, the pH of the water body increases, the content of ammonia nitrogen, nitrite, hydrogen sulfide and so on increases, and the root rot phenomenon of aquatic plants due to the lack of light will lead to the deterioration of the substrate and water quality, forming a vicious cycle.Preventive measures: in early spring, water level can be adjusted to improve water temperature.Before the arrival of plum rain season, do the following main work: one is to strengthen the crab pool disinfection, prevent the breeding of bacteria;Second, pay attention to water quality control, timely open oxygen generator, especially in the evening and after midnight to extend the boot time, adjust the water quality, improve the substrate;Three is the management of good water grass, timely removal of pool surface water grass and floating objects;Four is the right amount of feeding, timely increase or decrease the amount of bait, appropriately reduce the protein content of feed;Five is to pay attention to escape, rainfall is too large reinforcement block protection facilities, frequently patrol pool, escape prevention.3. Continuous high temperature and high temperature will directly or indirectly affect the water quality of crab pond. The change of water quality will have a significant impact on the normal growth and development of crab, which will slow down the growth rate of crab, increase the probability of failure in molting and increase the mortality rate.Preventive measures: adjust the water level in time and adjust the temperature with water;Improve water quality, replenish water, or regulate water quality with microbial agents.In the continuous high temperature weather, accurate feeding is needed to meet the needs of crab growth.Timely removal of residual bait, to prevent residual bait pollution of water quality;High temperature season to stop fertilization, to prevent water fertilizer caused by hypoxia crab pool.Four, hot hot weather high temperature, low air pressure hot weather easy to cause the crab pool water turbidity, poor water environment, reduced the amount of crab foraging.When the dissolved oxygen in water is lower than 3mg/L, there will be no feeding phenomenon. When the dissolved oxygen in water is lower than 2mg/L, the molting of crabs will be inhibited, and even suffocation will occur.Preventive measures: adjust the water quality of crab pond by adding and changing water;Open oxygenation facilities in time to maintain adequate dissolved oxygen;Strengthen the crab pond bottom quality and water grass management, to create a good growth environment for crab growth, to ensure the normal growth of crab.Five, flood and rainstorm easily cause crab pool water level to rise sharply, and even destroy the ridge of the pond, resulting in water plants sinking, rotting and pond water turbidity, algae pouring, hypoxia or hypoxia, crab stress response, physical decline, easy to cause secondary disasters such as disease.Preventive measures: make emergency preparations in advance before the occurrence of flood, timely repair of embankments and escape prevention, purse Seine and other infrastructure;After the flood to reduce the water level in time, discharge excess rain;According to the crab pond water quality, control the feeding quantity;We will strengthen water quality regulation to stabilize water and protect grass.Six, drought and less rain drought years, rivers, lakes, reservoirs and other water into the water level dropped sharply, the crab pool water supply difficulties, surface water grass drying dead or floating, rotting, some crab pool blue algae outbreak, crab growth slow, the molting period delayed or even do not molt, mortality rose.Preventive measures: it is necessary to timely coordinate the relationship between aquaculture water and other agricultural water, allocate scientifically, and ensure the aquaculture water;Artificial oxygenation in time to regulate water quality and maintain a good aquaculture water environment;Focus on preventing leakage of pond, scientific feeding, disease prevention and other work;Strengthen the management of input products to ensure the safety of river crab.Seven, the wind wind pond surrounding soil to the water, causing water turbidity, the bottom of the pool silt and organic matter easy to float, leading to the deterioration of water quality, the water sediment and other suspended matter too much can make crab breathing difficulties, the wind waves to the bottom of the pool of harmful substances quickly mixed into the water, the crab poisoning;And muddy water can make aquatic plant own photosynthesis is weakened, oxygen production function is reduced, cause crab pond hypoxia and cause loss.Preventive measures: it is best to protect the slope of the crab pool in advance, and the water peanut belt can also be used to prevent the impact of wind and waves, especially to avoid underwater operations in high winds, and pay attention to personal safety.Eight, fog fog weather pressure reduction, resulting in low oxygen content, light intensity, water surface tension increases, these factors directly affect the growth of algae, and prone to water change, algae and other circumstances, especially in the crab will be on the market before the harm is particularly serious.Preventive measures: timely opening of oxygen-increasing machine to increase oxygen, appropriate use of oxygen-increasing agent, to prevent the occurrence of hypoxia accidents.Avoid the use of oxygen-consuming drugs and preparations, such as bacillus, zeolite powder, disinfectants, algicides, etc., and properly reduce the feeding of bait.Nine, the sudden drop in temperature when the sudden drop in temperature, the surface water temperature drops, the water body produces strong convection, the crab is easy to produce stress response, the water body is easy to hypoxia, the crab appears ashore phenomenon.When the temperature difference is too large, the crab appetite is poor, and the crab with weak hepatopancreas function is easy to die.Preventive measures: when significantly cooling is forecast, the water level should be adjusted appropriately, the water level should be raised, the range of water temperature should be reduced, and the dissolved oxygen content of water body should be improved.Ten, air pressure plummeting air pressure plummeting, easy to cause dissolved oxygen in the water to reduce, coupled with increased oxygen consumption of microorganisms and zooplankton, crab will appear hypoxia ashore, climb the phenomenon of grass.Low pressure easily lead to rapid changes in water quality, crab will produce stress response, decreased immunity, disease occurrence and prevalence.Preventive measures: crab stress is strong, can use anti-stress and enhance nutrition drugs, improve resistance, enhance physical fitness.Strengthen crab pool management, prevent hypoxia, reduce pollution, re-change the bottom, more detoxification, anti-stress, waterproof change.When pressure suddenly changes, it is necessary to start oxygen in time;Timely appropriate sprinkling vitamin C, should stimulate and glucose ion calcium and other anti-stress agents.