Common causes of death of fish and its prevention

Due to farmland irrigation and the ebb and flow of the tide, the frequent flow of river water, the increased opportunities for the inflow of polluted water into the fish pond, or the pollution of the fish pond itself and sudden changes in the weather will cause dead fish. In order to enable farmers to accurately identify the cause of death of fish in daily production and management, and to take timely measures to prevent the occurrence of dead fish, this paper introduces the diagnosis and prevention of dead fish in several cases.

First, fish disease dead fish

1. Water body condition: the entry and discharge of pool water can only be completed under the condition of artificial control, and most of them are closed or semi-closed water bodies.

2. Symptoms of dead fish: generally speaking, there are obvious signs before the fish die. Such as loss of appetite, wandering alone, black body color, body surface bleeding or necrosis and other phenomena, some fish gills and body surface with the naked eye or under the microscope can see parasites, some fish open abdomen with ascites, intestinal anorexia, hyperemia inflammation and so on. Generally, the amount of dead fish is relatively small, and occasionally a large number of deaths are caused by fulminant fish disease, but the disease species are selective and die in large numbers for a single or a few species.

3. Prevention and treatment: in case of this situation, we should see a doctor in time and prescribe the right medicine to the case after diagnosis.

Second, dead fish in Fantang

1. Water body condition: the entry and discharge of pool water can only be completed under the condition of artificial control, which is a closed or semi-closed water body. The transparency of the water body is low and the water quality is fat.

2. Symptoms of dead fish: most of them occur in fish ponds with high fish density. When there is a sudden change in weather, when there is a thunderstorm or continuous overcast rain from afternoon to night, when the pressure is low, it is easy to cause fish flooding pond death. The time of death is often after 2 a. M. and before sunrise. If there are continuous rainy days, dead fish in floodponds may occur around midnight. Determination method: fish floating head, illuminated by electric light, fish because of light stimulation and issued a "wow" sound and temporarily sink into the water, and for a while all rise to the surface to swallow the air. The order of dead fish is generally mackerel-silver carp-bottom (bottom) fish, shrimp and wild miscellaneous fish all float on the surface of the pond. Generally speaking, big fish die earlier than small fish, and the mortality rate of big fish is higher than that of small fish. The dead fish have a white body and a protruding jaw.

3. Prevention and control: if the weather changes in ⑴, start the aerator in time. ⑵ pours fresh water into other rivers. ⑶ uses a pump to circulate water in the pool to make it flow. ⑷ can be sprayed with oxygenating agents to increase oxygen when necessary.

Third, pollute dead fish

1. Water body condition: the water body is generally open or sewage from pollution sources near the fish pond is discharged directly into the pond. The water color suddenly changes color (black, red, gray, etc.), accompanied by peculiar smell.

2. symptoms of dead fish: in the early stage of pollution poisoning, the fish collided, jumped up and down, and swam rapidly. The occurrence of dead fish is sudden, without any precursors, the death rate is very high, and the species selectivity of dead fish is not obvious, there is no time rule, as long as there is the inflow of contaminated water, there will be a large number of deaths. In the later stage of poisoning, the diseased fish showed weakness, loss of balance, dying, sinking and death. Due to different pollution sources, some fish have attachments on the body surface, especially in the gills, and usually have specific smells of poison, and some fish gills have obvious symptoms such as hyperemia and curvature of the spine.

3. Prevention and control: block the inflow of pollution sources, if possible, add new water in time, adopt the way of drainage and irrigation at the same time, dilute the pollutants, reduce the pollution degree and reduce the pollution loss.