What are the common causes of fish death? A detailed guide to prevention methods

Due to farmland irrigation and the rise and fall of tides, river water flows frequently, increasing the chances of polluted water flowing into fish ponds, or the pond's own pollution combined with sudden weather changes can all cause fish deaths. In order to help farmers accurately identify the causes of fish death in daily production and management, and promptly take measures to prevent fish deaths, here are the diagnosis and prevention methods for fish deaths under several circumstances:

1. Fish deaths from disease

1. Water body conditions: The intake and discharge of pond water generally can only be completed under human-controlled conditions, and most are closed or semi-closed water bodies.

2. Symptoms of dead fish: Generally, fish show fairly obvious signs before dying. Such as reduced appetite, swimming alone away from the group, darkened body color, bleeding or necrosis on the body surface, etc. Some fish have parasites visible to the naked eye or under a microscope on the gills and body surface, and some fish, when the abdomen is cut open, show ascites, empty intestines, congestion and inflammation, etc. Generally the number of dead fish is relatively small, and occasionally mass deaths occur due to explosive fish disease, but the diseased species are selective, with a single or a few species dying in large numbers.

3. Prevention and treatment: When encountering this situation, seek diagnosis promptly, and after confirmation, apply the right medicine.

2. Fish deaths from pond turnover

1. Water body conditions: The intake and discharge of pond water generally can only be completed under human-controlled conditions, and it is a closed or semi-closed water body. Water transparency is low and the water quality is relatively fertile.

2. Symptoms of dead fish: Most occur in fish ponds with high fish density. When there is a sudden weather change, a thunderstorm from afternoon to night or continuous overcast and rainy days, or stuffy hot weather with low air pressure, it easily causes fish to die from pond turnover. The time of death is often after 2 a.m. until before sunrise. If there are continuous overcast and rainy days, pond turnover deaths may occur around midnight. How to judge: When fish float to the surface, shine an electric light on them; the fish make a "splash" sound due to the light stimulus and temporarily sink into the water, then after a while they all float up again to gulp air. The order of death is generally bream - silver carp - bottom-dwelling fish, and shrimp and wild miscellaneous fish all float at the water surface near the pond edge. Generally large fish die before small fish, and the mortality rate of large fish is higher than that of small fish. Dead fish have a whitish body color and a protruding lower jaw.

3. Prevention and treatment: (1) When there are weather changes, promptly turn on the aerator. (2) Add fresh water from the outer river. (3) Use a water pump to circulate water in the pond so that the pond water is in a flowing state. (4) When necessary, spread oxygen-increasing preparations to boost oxygen.

3. Fish deaths from pollution

1. Water body conditions: @#@233@#@ The water body is generally open, or there is a pollution source beside the fish pond discharging sewage directly into the pond. The water color suddenly changes (black, red, gray and other abnormal colors), accompanied by an unusual odor.

2. Symptoms of dead fish: In the early stage of pollution poisoning, fish show colliding, jumping up and down, and rapid swimming. Fish deaths occur suddenly, without any warning signs, and the death rate is very high. Moreover, the species selectivity of dead fish is not obvious and there is no time pattern; as long as polluted water flows in, mass deaths will occur. In the later stage of poisoning, sick fish show weakness, loss of balance, being at their last gasp, and sinking to die. Due to different pollution sources, some fish have attachments on the body surface, especially the gills, and usually a distinctive toxic odor, and some fish show obvious congestion of the gills, curvature of the spine and other symptoms.

3. Prevention and treatment: Block the inflow of pollution sources. If conditions permit, promptly add fresh water, and adopt the method of draining while filling to dilute pollutants, reduce the degree of pollution, and reduce pollution losses.