The continuous freezing rain and snow conditions make the aquaculture water ice, resulting in lack of oxygen in the water under the ice, resulting in a large number of overwintering fish deaths; continued cold and rainy weather, easy to affect the seed production, leading to the hatching rate of eggs, fertilization Low eggs, resulting in low seedling rate, but also easily lead to rapid deterioration of water quality, frequent disease, leading to low aquaculture production. Therefore, measures should be taken to reduce the impact of freezing weather on the aquaculture industry.
Frozen fish harmless treatment technology
Frozen rain and snow disasters are likely to cause a large number of fish frostbite to freeze and die. To prevent pathogens from spreading and contaminating aquaculture water, and prevent improper handling of public health hazards, a large number of frozen fish must be treated in a harmless manner.
Clear fishing: remove dead fish in water bodies and bottom mud in time to prevent the growth of pathogens and cause pollution in aquaculture water bodies.
Deep burial: Frozen fish can be buried deep after disposal. Buried should be chosen away from water, rivers, aquaculture and residential areas. First, dig a deep pit. When burying, first lay 3cm thick quicklime on the bottom of the pit, then place the frozen fish in the pit, then sprinkle a layer of quicklime, then cover with the soil, and keep it flat with the surrounding. The thickness of the cover soil should be not less than 0.6 m; if there is a suspected disease or other abnormal conditions, the dead fish must be burned and then covered with a layer of soil more than 2 meters thick; the filling should not be too solid, so as not to cause air bubbles and liquid leakage due to gas production. Clear identities should be set after burial.
Fermentation: Freeze-dead fish can be selected for fermentation treatment away from water sources, rivers, and breeding areas. First, dig a fermentation pit, cover it with plastic film on the soil, place the frozen fish in the pit, seal it with a plastic film, cover it with soil, and use it as an agricultural fertilizer after fermentation.
Disinfection of water body: When the aquaculture water body of frozen fish that has suffered frostbite is discharged, it must be disinfected before reaching the national wastewater discharge standard before it can be discharged into natural waters.
Disinfection method: When the clear pond is used bleach (containing 25% of available chlorine) Quanchiposa.
Tools: Sterilize fishing, transportation, loading and unloading tools with bleach.
Disinfection method: Spray or soak with a solution of bleach (containing 25% of available chlorine).
Overwintering and Snow-Reducing Disaster Reduction Techniques for Fishes in South China
The severe winter and snow seasons are the peak seasons for fishing, fishing, and listing. They are also a critical period for the overwintering of wintering varieties in greenhouses. Adopting comprehensive technical measures to ensure the safe wintering of aquatic products is an important part of the anti-snow disaster reduction of fishery production.
Strengthen on-duty according to the weather conditions, timely understand the snowstorm warning information, do a good job of antifreeze and pressure collapse.
Do a good job in the maintenance of aquaculture insulation facilities, and prevent the adverse effects of snow storms and cooling. The timely removal of snow will prevent the collapse of greenhouses and greenhouses, ensure the safety of personnel, farmed fish and aquaculture facilities, and ensure that the cultured species will safely pass winter.
Reinforce the repair facilities, timely repair the collapsed production facilities; increase the support for the bent steel sheds, etc., to ensure no deformation; damage to the shed film should be replaced as soon as possible.
Intensified heating and insulation of farmed fish in facilities. Insulation measures: The inner insulation layer can be increased by double-layer plastic film to strengthen the greenhouse insulation effect; strengthen the reserve of heating energy, enhance the heating capacity, and ensure normal heating; increase auxiliary heating facilities such as heating plates to increase the water temperature; Boiler spare heat for bad weather.
Enhances the oxygenation effect to avoid the death of fish due to lack of oxygen and water quality. (1) Prevention of ice formation in ponds: In a pond that has not yet been frozen, impeller-type aerators with a capacity of more than 1.0 kW per acre are used, and aerators are continuously turned on for 24 hours to prevent ice formation. (2) Anti-anoxia technology in icing ponds: If the pond is already frozen and the snow cover is over, the ice can be broken within 3 meters around the pond, allowing light to penetrate into the water and preventing fish and shrimp from being lacking. oxygen.
Grasping the fishing market, making full use of fishing, transportation tools, and catching up with the listing, to avoid damage caused by snow disaster aquatic product pressure pond.
Anti-snow Disaster Reduction Technology for Fishes in Northern China
After the winter, the harsh climate of ice and snow will easily lead to different levels of ice-ice in winter pond fishes. The so-called “winter ice†means that when the water is not frozen in the early winter, it encounters snowfall and floats on the water surface. Without melting snow, if the weather suddenly becomes cold, the water temperature drops rapidly, and the water and snow mix together, forming an opaque layer of ice over the winter water surface. "Wu Bing" can easily lead to lack of oxygen in the aquaculture water. Dead fish accidents caused by lack of oxygen occur from time to time, posing a great threat to the safe wintering of fishery.
For Wubing ponds, mechanical oxygenation and drug emergency can only be used. Mechanical oxygenation can be achieved by the use of impeller aerators to increase oxygen, circulating water inside the pond to increase oxygen, attracting river water and large surface water to make up water and increasing oxygen, and taking oxygen from nearby ponds to supplement water and increase oxygen. The use of mechanical aeration should pay attention to the time can not be too long, the amount of water conduction can not be too large, try to prevent the stress response of fish. The use of a chemical oxygenating agent to rapidly and efficiently increase oxygen in the pool can be used for emergencies, and the effect is good. However, due to the high cost, it can only be used for rescue purposes. In the event of an emergency, aeration can be performed using chemical agents such as aerobic oxygen. Strong oxygen water purification agent is currently a very good chemical oxygenation agent, other commonly used chemical oxidants are calcium peroxide, sodium perborate, sodium percarbonate, hydrogen peroxide, etc., in case of emergency use. The use of chemical oxygen must pay attention to the appropriate amount, not too much, so as not to cause damage to the fish.
In order to reduce the damage caused by ice to pond fish farming, the following aspects should be done in peacetime:
The amount of dissolved oxygen in wintering pond water is regularly tested: it must be tested once a week, once every three days during the Spring Festival, and once a day after the Spring Festival. Water bodies with dissolved oxygen below 5 mg/l should be tested once a day.
When dissolved oxygen is reduced to 3 mg/L, oxygenation measures should be taken in time
(1) Biological oxygenation: Remove iced ice in places where conditions permit, re-clear open ice, and adopt bioaerobic methods. The area where the ice floes are broken up accounts for more than one-third of the total area of ​​the pond, ensuring that the phytoplankton can produce oxygen by photosynthesis; and clearing the ice should promptly sweep the snow.
(2) Mechanical oxygenation: When using mechanical oxygenation, the dissolved oxygen and water temperature should be monitored regularly. When the dissolved oxygen content reaches 3 mg/liter or more, oxygenation should be stopped. When the water temperature drops below 2°C, the water injection should be stopped immediately. , so as not to cause stress reaction of overwintering fish.
(3) Water injection and oxygenation: For ponds with external water sources, new water with higher dissolved oxygen may be added periodically to increase oxygen, such as near pond water and river water. If the water-soluble oxygen in the water source is low, the stroke and drop can be increased, and the oxygen content can be increased and then injected into the pool.
(4) Chemical oxygenation: For severely hypoxic bodies of water, chemical oxygenation may be used, and peroxides and other oxygen-reducing agents may be locally splashed. However, due to the higher price of drugs and the greater impact on water quality, it is not appropriate to use them for a long period of time and in large quantities. It should be used as a short-term emergency measure and other methods of supplementing oxygen should be adopted.
Strengthen disease monitoring and do a good job in disease prevention and control
(1) Strengthen monitoring of post-disaster epidemics and raise awareness of disease prevention; increase the monitoring of sudden and explosive epidemics of non-hardy-tolerant species, and increase the capacity for emergency response.
(2) Putting prevention and treatment into practice. One is to remove the dead fish caused by hypoxia in time for harmless treatment; the second is to avoid stress response and reduce the death of farmed fish; third is to properly use water quality improvement, regulation, disinfectant and disease treatment drugs. Reduce the death of farmed fish; Fourth, purchase disinfectant such as salt, lime, and potassium permanganate, disinfect the cultured fish after ice and snow melting, and improve the response capacity; Fifth, strengthen the management of culture and improve the body of cultured fish. Resistance and defense capabilities.
(3) Prevent watery mildew from occurring. Saprolegniasis is a common disease in freshwater fish farming in China, and it is easy to cause a large number of fish to die. The harm is particularly serious.
The hydrophila has a wide range of adaptability to water temperature, and it can grow at 5°C~26°C. The optimum growth temperature is generally 13°C~18°C, but the strains are slightly different. Some strains may even have a water temperature of 30°C. Growth and reproduction. In addition, its spores are also widely found in natural water environments. They are extremely resistant to adverse environmental conditions. There is no aquaculture environment in which aquatic fungi are not present. Once suitable parasitic conditions occur, they will be parasitic on fish wounds. Causes hydromycosis. It can be seen that although the severe ice and snow weather caused a significant reduction in water temperature, which may cause aquatic molds to be difficult to grow and multiply and even die, their zoospores are still present in a large number in aquaculture waters. Therefore, the pathogenic factors of outbreaks of water mold are still present.
Severe changes in temperature within a short period of time are important conditions affecting the infection of aquatic fungi. It intensifies the infection intensity and speed of aquatic molds on fish. Severe cold weather such as cold waves and heavy snowstorms are likely to result in poor breathing of large freshwater fish, reduced immunity, and damage to the body. This will increase the chance of infestation of aquatic fish by the aquatic mold and increase the risk of outbreaks of water mold disease. Therefore, when freezing rain and snow come, it is necessary to do the following work to prevent the occurrence of watery mildew: 1) Strengthen the cold and warmth of fish, prevent freezing and prevent injuries, and strengthen the cold windproof shed at the upper winds of overwintering fish ponds. Or sprinkle the straw in the pond to prevent convection in the pool and prevent the temperature of the water from falling sharply; 2 to strengthen fish cultivation in the fall, feed high-quality feed, enhance the body composition of overwintering fish, and enhance the resistance of the fish body; 3 pay close attention to observe the winter If there is leakage in the pool, if it is found that the ice surface collapses, it should be replenished in time; 4 often measure dissolved oxygen, pay attention to the dissolved oxygen in the wintering pond water, can be measured 1 to 5 days to 7 days, 1 day to 2 days before and after the Spring Festival 1 Times, in order to take oxygenation measures in time, such as playing ice eyes on the ice, the aerator will be fixed on the ice eyes for oxygenation; 5 often cleaning the snow on the ice and dust, keeping the transparency of the ice, improve Transmittance to promote the photosynthesis of phytoplankton in water; 6 The dead fish should be promptly cleaned, disinfected and buried in the pond so as not to contaminate breeding water and water mold on the wound; 7 before the cold wave and after melting ice The temperature rises steadily, especially when the water temperature reaches 5°C, timely use of disinfecting and disinfecting drugs for Quanchiposa, and at the same time, improve water quality and inhibit the growth and reproduction of aquatic molds; 8 For the ponds that have outbreaks of water mildew, do a good job of isolation. To prevent the spread of watery mildew, and at the same time treat with water mildew prevention and treatment drugs.
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