Analysis of the Causes of Explosive Fish Mortality and Prevention and Control Measures

2. Countermeasures for bacterial and parasitic diseases

For bacterial diseases, the main approach is to control the reproduction of pathogenic bacteria in the pond water and keep their numbers below the disease-causing threshold. This requires routine regular disinfection, using "Yujunjing", "Yujunjing No. 2", "Jundi" or strong chlorine powder once every 7-10 days to prevent excessive reproduction of pathogenic bacteria. After a bacterial disease occurs, disinfect continuously 2 times with a disinfectant, and at the same time mix drugs such as "Chuxueping", "Jingbo Baoxueping", "Yubingkang", "Yufubao" or "Jianyule" into the feed for oral administration, continuously for 3-5 days as one treatment course, which can effectively prevent the spread of bacterial diseases in fish and promote the recovery of the fish body. For parasitic diseases, during the peak season of parasitic diseases, drugs such as "Miechongjing" or "Miechongjing No. 2" can be used regularly for prevention. After a parasitic disease occurs, use a microscope to confirm which parasite is causing it, then use the appropriate insecticide to kill the parasites, and at the same time splash a disinfectant once to disinfect the water body to prevent secondary bacterial infection.

3. Countermeasures for the effects of nutritional metabolism

For ponds that have been fed pelleted compound feed for a long time, when conditions permit, appropriately supplement with some natural feed, such as green feed like water plants, and stop feeding pelleted feed for a period. At the same time, regularly mix into the feed and administer drugs that protect the liver and support liver function and strengthen the liver and promote bile secretion, such as "Gandankang", "Jianganbao", "Ganweile", etc. The effect is better when used together with "Vc specially for aquaculture". This can effectively prevent the occurrence of fatty liver and hepatobiliary syndrome.

4. Countermeasures for the effects of water quality and environmental factors

This is mainly caused by excessive levels of ammoniacal nitrogen and nitrite leading to fish deaths. After 40-50 days of culture, these two indicators in the water body both exceed the standard to varying degrees, and when the pH is also on the high side, it is very easy to cause ammonia and nitrite poisoning and lead to massive acute fish deaths. During the culture process, microbial preparations such as "Huohua Lishengsu", "Yijunduo", and EM bacteria preparations should be used regularly once every 15 days. When the pond bottom deteriorates severely, bottom quality improvers such as "Shuangxiao Dijing", "Duoyang Digaiwang", and "Digai Zhuanjia" can be used in combination, which can greatly eliminate the levels of ammoniacal nitrogen and nitrite in the water body, maintain a good culture environment, and prevent massive fish deaths caused by excessive ammoniacal nitrogen and nitrite.

5. Countermeasures for toxic poisoning

Once fish poisoning occurs, it must be handled promptly and decisively, quickly removing the toxic substance, and at the same time taking measures for symptomatic treatment. When poisoning by disinfectants, insecticides or pesticides occurs, immediately change a large amount of water, introduce clean water sources, remove the fish from the poisoned environment, and use appropriate detoxifying drugs for neutralization and precipitation treatment to eliminate residual toxic substances and prevent further absorption of the toxic substances. At the same time, use glucose, baking soda, "Jiedu Jiuxing" and other drugs to relieve various functional disorders caused by poisoning in fish, alleviate poisoning symptoms, and restore physiological functions. For toxic substances already absorbed by the fish, appropriate drugs should be selected to reduce the concentration of toxic substances in the blood and block the effects of the toxic substances. For example, when organophosphorus poisoning occurs in fish, atropine can be used to remove the toxic substances from the fish body. For the phenomenon of fish death caused by ingesting toxic substances, this is mainly caused by eating moldy pelleted feed and extracted rapeseed cake. This phenomenon focuses on prevention. As long as the feed is kept fresh and moldy feed and extracted rapeseed cake are not fed, food poisoning will not occur.

The author has noticed that due to careless management, explosive fish mortality occurs from time to time during the culture process, and incidents that leave aquaculture operators with total crop failure are repeated again and again, which is very distressing. In fact, explosive fish mortality focuses on prevention, and when bad signs appear, they should be dealt with promptly. As long as prevention work is done well and management work is carried out properly, the chance of explosive fish mortality should be able to be minimized.