In the process of aquaculture production, the sudden and massive death of fish in the pond often occurs in season, weather and morning and evening. Dinner may be normal, but a large number of fish died in the pond at night or early in the morning. What is the cause of the large number of fish deaths in the pond? In the process of providing technical services at the grass-roots level, the author often receives similar consultation calls. Now, this paper introduces the causes of a large number of pond fish deaths. < P > How to correctly judge what the pond fish died of? It can be judged from the following aspects:

Fish in the pond are poisoned by pollution. Fish in the pond are concave and convex due to lack of oxygen. Fish in the pond suddenly caused disease.

it can happen at any time regardless of season, weather and day and night. However, ammonia-nitrogen poisoning of fish often occurs in continuous sunny days and afternoons. Drug loss is related to farmland fertilization, intonation reagent or factory pollution. Especially in the growing season of crops, during the epidemic of pests and diseases, and during the epidemic of language diseases, the phenomenon of dead fish may occur during the day and night.

It mostly occurs in the high temperature season in summer and autumn, especially around the two solar terms of barley yellow or Bailu flood. High temperature season, continuous low pressure and sultry weather, continuous plum rain, shower weather, and often occur between midnight and dawn. The fatter the water quality, the higher the stocking density, and the higher the possibility and severity of tigers.

A large number of deaths occurred in the seedling planting stage and during the high temperature in summer before and after the two solar terms of barley yellow or Bailu flood, and the number of deaths gradually decreased. In particular, foam disease, fulminant hemorrhagic disease and grass carp "three diseases" may cause a large number of deaths in a short period of time.

Generally, there is no trace of floating, and its symptoms vary from poison to poison. When fish are poisoned by ammonia nitrogen, they are short of breath and walk around. In some ponds, silver carp even jumps on the ridge of the field, sometimes surfaced, breathing slows down, and the fish floats up and dies immediately. (William Shakespeare, Hamlet, famous sayings of meat) (Weak poisoning, fish wharf phenomenon is not obvious, and symptoms vary from poison to poison. Some manifestations are slow response, paralysis, slowly turning black, increased mucus, loss of activity and death. Some people showed trembling, jumping and struggling until they died in a coma.

Fish appear scattered on the grass, gather their mouths together, and quietly inhale oxygen directly from the sleeping air. In severe cases, mackerel and mackerel floating in shallow water in the pond will slowly turn over, and in order to keep their balance, they struggle and die several times.

fish are often accompanied by typical symptoms. After naked eye observation, it was found that the fish's body surface (such as orbit, gill cover, mouth, chin, lower fin, both sides of abdominal cavity, etc.) was bleeding, gill cover opened the "skylight", anus was red, and symptoms such as dental caries, dental caries and rotten tail were found. The fry < P > Depending on the type of poison, other fish would die. After ammonia nitrogen poisoning, some fish may die regardless of their size and species. Drug poisoning sometimes dies from other fish because of different kinds of drugs. For example, Dyson ammonium poisoning is very toxic to the edible fish in the pond, and the mortality rate is high. Sometimes, regardless of the drug type and the size of the fish, even the toad in the pond may die.