Prevention and control of water mildew in cultured freshwater Pomfret during overwintering

1. Diseases that often occur during the overwintering of freshwater Pomfret

The most common fish diseases in the overwintering period of freshwater white Pomfret are water mildew, melon disease, rotifer disease, oblique tube disease and so on, especially melon disease, which is easy to cause explosive death. The causes of various fish diseases are due to low water temperature during overwintering, no feeding of fish, high physical consumption, poor physique, or damage or frostbite caused by careless fishing and transportation in low temperature weather, which is caused by a large number of parasites and bacteria to invade and endanger the fish. Therefore, it is necessary to take the epidemic prevention policy of "prevention first". While keeping warm through the winter and strengthening feeding and management, we should also do a good job in disease prevention and control. Before entering the pond, the fish should be bathed with 4%-5% salt water for 10-15 minutes. If there are diseased fish, they should be treated in time. But when using medicine, do not use trichlorfon and malachite green.

2. Water mildew

Water mildew is the most common and harmful disease of freshwater Pomfret during overwintering, especially in fish ponds at the beginning of spring.

(1) pathogen

Water mold, cotton mold.

(2) symptoms

A lot of cotton-like white hairs can be seen on the body surface of diseased fish (in the early stage of infection, no symptoms can be seen with the naked eye). Most of the diseased fish swim slowly on the surface of the water, lose appetite and lose weight, resulting in death.

(3) Prevention and control methods.

① tries to avoid fishing and transporting fish species in low temperature seasons to prevent mechanical damage and frostbite. Especially after the beginning of spring, the fish species should be caught and transported only after the water temperature is stable above 22 ℃ and the fish body is restored by feeding.

Before overwintering, ② should deepen the pond water so that the water depth is more than 2 meters, or take other heat preservation measures to keep the water temperature above 19 ℃ to prevent frostbite. At the same time, we should pay attention to the water environment to avoid water quality is too fat, the water color is brown, light yellowish green.

When ③ fish species are transported, about 1% salt should be added to the transport water body for sterilization and disinfection; when the fish species pass through the pond, they should be soaked in 1%-2% salt water for 5 minutes and then cultured in the pond.

Fish ponds with ④ disease can be sprinkled with 0.04% salt in the whole pond, or 0.04% baking soda can be added to the whole pond at the same time, or 2.5 kilograms of calamus leaves per mu of water, 0.5 kilograms of salt and 2 kilograms of human urine can be added to the whole pond after soaking for 24 hours.