After the frost falls, the water quality ages, and algae, pan-bottom, fungal and parasitic diseases all come

The frost festival contains the meaning of the weather getting colder and the first frost appears, which is the last solar term of autumn and also means the beginning of winter.

After the frost falls, the temperature gradually drops in various places, the temperature difference between day and night increases significantly, and the water quality of the pond gradually ages, which is easy to induce fungal and parasitic diseases of aquatic animals. Aquaculture has also entered the harvest season, and fish, shrimp and crabs have been caught and marketed.

The northern region has entered the preparatory stage before wintering, and it is necessary to pay attention to the intensive cultivation of overwintering seedlings; most of the southern region is still a good growth period for breeding species, and when catching and pulling nets, we must pay attention to the impact on the breeding objects to avoid diseases caused by mechanical damage.

First, the characteristics of frost fall:

1, the biggest climate of frost is characterized by a large temperature difference between day and night, hot at noon during the day, but the night will be very cool, and the temperature difference between day and night is even more than 10 ° C;

2. The north wind and the northeast wind are the majority, and the pond environment is unstable;

In particular, cold air descends south from time to time, and ponds are prone to inverted algae or pan-bottoming, resulting in a large number of deaths of breeding objects;

Second, the characteristics of the culture pond:

1. The temperature difference between the upper and lower water layers of the pond is large, which is easy to cause water stratification and lack of oxygen at night;

2. The pond is in the middle and late stage of aquaculture, the water quality and substrate pollution are serious, and a large number of harmful bacteria and parasites are easy to breed; and the pond load is aggravated, which is prone to hypoxia;

3. The eutrophication of the water body is serious, the algae is single, and it is easy to "inverted algae";

4. The accumulation of dead algae, residual bait and feces is more, and the toxic and harmful substances such as ammonia nitrogen and nitrite are increased;

Third, the characteristics of fish body health status:

1. The amount of feed is large, the amount of fish feeding is relatively high, and the burden on the liver and digestive system is aggravated;

2. The saturation of dissolved oxygen in the water is low, the fish is in a state of hypoxia or hypoxia for a long time, the fish has poor physique, and it is very easy to be infected by pathogens, especially parasites or bacterial infections;

3. In the early stage of breeding, due to the use of too many antibacterial drugs and antibiotics, the fish body develops drug resistance, so that the treatment effect is not ideal at the later stage;

4. Common diseases

1. Water mold disease: freshwater farmed fish can occur, the prevailing water temperature is 10 °C ~ 20 °C, and all breeding areas need to be prevented.

2. Infectious hematopoietic organ necrosis: the main object is rainbow trout, the water temperature of the disease is 8 °C ~ 15 °C, the younger the fish age, the more sensitive to the disease. Beijing, Hebei, Liaoning, Shandong, Gansu, Qinghai and other concentrated flow-stream aquaculture areas need to be paid attention to.

3. "Gill bleeding" disease (pathogen is carp herpes virus type 2): the main object is crucian carp, and the water temperature of the disease is 15 °C ~ 25 °C. In the past two years, the incidence of the disease in the main breeding area of heterogeneous silver crucian carp in Jiangsu Province is more serious, and it has also occurred in Hebei, Hubei, Anhui and other breeding areas, showing a trend of spread in many places, and the main crucian carp rearing areas such as Jiangsu, Hebei, Jiangxi, Anhui, Hubei and Hunan need to be key prevention and control.

4. Koi herpes virus disease: the main objects of occurrence are carp and koi, and the water temperature of the disease is 18 °C ~ 30 °C, especially in 22 °C ~ 28 °C. Guangxi, Jiangsu, Henan, Hebei, Shandong, Sichuan and other places need to focus on prevention and control.

5. Catfish intestinal sepsis: the main object of occurrence is spotted forktail catfish, and the popular water temperature is 24 °C ~ 28 °C. Anhui, Jiangxi, Hubei, Hunan, Guangdong, Sichuan and other catfish concentrated aquaculture areas need to focus on prevention and control.

6. Ringworm disease: mainly harmful to grass carp, silver carp, bighead carp, carp, eel and other fish, especially fish species are most susceptible to infection. The suitable water temperature for the propagation of most species of ringworms is 20 °C to 25 °C. Prevention is needed in all freshwater fish rearing areas.

7. Small melon worm disease: small melon insect breeding suitable water temperature 15 °C ~ 25 °C, a variety of freshwater fish, migratory fish and ornamental fish can be infected, especially in fish species susceptible.

8. River crab tremor disease: the object of occurrence is river crab, pond, rice field, reed field, net enclosure culture of river crab will occur, Jiangsu, Liaoning, Anhui, Hubei and other river crab breeding areas need to focus on prevention.

5. Prevention and control measures

1. Pay attention to water quality regulation. Fish, shrimp and crabs have entered the late stage of grow-out, their own pollution will be aggravated, pay close attention to changes in water quality, regularly use quicklime or chlorine disinfectant to disinfect the aquaculture water body, regularly use substrate modifiers or micro-ecological preparations to improve the growth environment, so that the aquaculture water body always remains "fat, live, tender and cool".

2. Scientific and reasonable feeding. According to the weather, water temperature, pond storage and eating conditions of reasonable feeding of high-quality feed, multivitamins and immunogeosaccharides can be added to the feed to enhance the disease resistance of breeding objects.

3. Strengthen production management. Pay close attention to weather changes, patrol the pond in time, and turn on the aerator in a timely manner to prevent floating heads. Varieties that reach the commercial specifications should be fished and listed in a timely manner to maintain a reasonable stocking density in the breeding pond.

Sixth, there are four major misunderstandings in pond management before and after frost falls

1, misunderstanding one: the temperature is suitable, fish eat well, as much as possible feeding

After a rainy day, many farmers will increase the amount of feeding when it is sunny. But in fact, feeding too much is not a good thing, the fish body because of the digestion of food to increase the consumption of dissolved oxygen in the water, if the water dissolved oxygen is insufficient, it will not only affect the conversion rate of feed, but also induce the occurrence of viral diseases and bacterial diseases;

2, misunderstanding two: the wind can be oxygenated, do not open the aerator

Strong winds can indeed play a role in oxygenation, but before and after the frost fall, most of the north winds and northeast winds, which can easily lead to the bottom of those ponds with poor bottom quality, and even cause hypoxia;

3. Myth 3: Excessive insecticidalization and sterilization to prevent fish disease

Usually do not change the bottom and water transfer, do not strengthen the physique of fish, blindly through insecticidal, sterilization, disinfection to control the occurrence of diseases. However, excessive insecticidal sterilization, it is very easy to cause stress and even poisoning, aggravate the occurrence of disease, and will cultivate parasite and bacterial resistance, once the fish dies, it is difficult to take medication to treat;

4, misunderstanding four: find ways to reduce nitrite

With the increase of feeding, the pollution of ponds increases, and the nitrite of those ponds that usually do not pay attention to bottom change and water transfer remain high, relying on the use of rapid downpour drugs, causing large changes in water quality, which is also a kind of stress for fish.

VII. Suggestions for pond management after frostfall:

1. For ponds with heavy loads, appropriate fish can be selected to reduce the density of aquaculture and reduce the load of ponds;

2, poor water quality of the pond, sunny day at noon to open more aerator, early in the evening to open the aerator, conditional can be a small number of times to replace the new water, increase the dissolved oxygen of the water body; appropriately increase the beneficial algae, reduce the floating phenomenon due to lack of oxygen;

3. Regularly change the bottom, remove harmful substances such as ammonia nitrogen, hydrogen sulfide and nitrite at the bottom of the pond, which can effectively reduce the reproduction of parasites and harmful bacteria, achieve the purpose of insect suppression and bacteriostatic, and reduce the incidence of fish;

4. Regular use of water transfer products, effective water transfer and stabilization of water quality, timely decomposition of organic matter, to avoid water quality deterioration caused by eutrophication of water bodies, resulting in decreased fish immunity.

In short, after the frost falls, we must pay close attention to weather changes, timely patrol ponds, open-air breeding should pay attention to antifreeze, winter shed breeding should pay attention to ventilation and heat dissipation during the day. According to the weather, water temperature, pond storage and feeding conditions, reasonable feeding of high-quality feed, regular inspection of the presence of parasites, while carefully checking for enteritis and other diseases, to prevent the outbreak of bacterial diseases and parasitic diseases.

Special attention: for wintering fry that are afraid of cold, they should build a wintering shed from the end of October to November to avoid the phenomenon of low temperature death after December!