1 Causes of diseases during and after wintering

1.1 Various diseases due to shallow water, seepage and frostbite

1.2 Hypoxia, floating head

1.3 Dissolved oxygen supersaturation bubble disease

1.4 Various diseases caused by net injury

2 Safe wintering

2.1 The key to safe wintering

2.11 Appropriate amount of dissolved oxygen

The main source of dissolved oxygen: photosynthesis of phytoplankton

2.12 The main reasons and solutions for low dissolved oxygen

2.121 The water is thin and the amount of phytoplankton is low

Prevention and solutions: Introduce algae seeds and apply fertilizers based on inorganic fertilizers

2.122 Zooplankton (protozoa, rotifers, cladocerans, copepods, etc.) multiply in large numbers, and the water body consumes a lot of oxygen

Prevention and solutions: ① Change the bottom before freezing to reduce organic impurities in the water; ② Appropriately use some chemicals to kill zooplankton; ③ Use oxygen-enhancing equipment (such as nanotubes, etc.) or water aeration method

2.123 Low light intensity

Prevention and solution: keep the ice surface smooth and transparent; clear the snow in time after snowfall, and keep at least two-thirds of the ice on the ice surface; often remove the floating soil on the ice surface to improve the transparency.

Causes and Solutions of Dissolved Oxygen Supersaturation

1) Large amount of phytoplankton and high oxygen production

2) Excessive dissolved oxygen cannot be discharged

3) An increase in water temperature

2.12 Appropriate water temperature

In the north, during the wintering of freshwater fish, when the water temperature is lower than 0.5 ℃, carps will suffer from frostbite. The common causes of frostbite are as follows:

2.121 Symptoms of hypoxia floating head often occur.

2.122 The water under the ice in the wintering pond is shallow, less than 1.5 meters.

2.123 Ponds do not hold water (often seepage) resulting in shallow water under the ice.

2.124 Long-term aeration to raise water.

2.13 The ideal wintering water temperature is generally 1~2℃. The specific reasons are as follows:

2.131 Under the water temperature of 1~2°C, cultured fish can maintain the lowest metabolic level, and the energy consumption in the fish can be reduced to a minimum, and it is harmless to the fish.

2.132 In the waters at this temperature, other biochemical processes basically stop, reducing the consumption of oxygen, which is more conducive to safe wintering.

2.133 Excessive water temperature will increase the metabolic function of farmed fish, consume a lot of physical energy, and reduce production when marketed.

According to the vertical distribution of water temperature under the ice, in theory, it is safer to overwinter in a water depth of 1.5 meters under the ice. Therefore, in order to ensure the safety of fish overwintering, the water depth under the ice should be kept at least 1.5 meters or more.

2 Ways to winter safely

2.1 Treatment before wintering

2.11 Before overwintering, the overwintering fingerlings should be carefully fed to increase the accumulation of fat and improve the plumpness. The specific measures are to increase the feeding of feeds containing more fat and sugar to fatten from the beginning of autumn to the wintering period before the food is stopped.

2.12 Strictly disinfect the fingerlings, water quality and substrate, and minimize net damage when dividing ponds.

2.2 Selection of overwintering ponds

 Site selection: choose leeward, there are no trees or buildings around to block the sun, try to be as long as possible from east to west and short from north to south to increase or decrease the illumination.

 Depth: The average water depth that the pond can accommodate is at least 2 meters to ensure safe wintering.

 Features: No water seepage and water leakage.

2.3 Water quality adjustment and stocking of fingerlings

2.3.1 Clean and disinfect ponds. Purpose: To kill various pathogenic microorganisms, zooplankton and excessive sludge in the pond.

2.3.2 Water injection, the depth of pond injection water is generally more than 2 meters.

2.3.3 Fertilizer water, if there are a lot of zooplankton in the water before fertilizer water, they should be killed. In order to increase the phytoplankton in the water, inorganic fertilizers are mainly applied. Use as little or no organic fertilizers as possible to avoid the production of a large number of zooplankton in the later stage to consume dissolved oxygen in the water.

2.3.4 Stocking of fingerlings: During the stocking process, a reasonable density should be maintained, and net damage should be minimized during the process of drawing nets and ponds.

3 The following methods should be adopted for the fish species that directly overwinter in the original pond without pond treatment:

3.1 Ensure sufficient water depth (more than 2 meters)

3.2 If there are a large number of zooplankton in the water, they should be killed

3.3 Use chemicals to improve the substrate and water quality to reduce organic impurities in the water and eliminate the breeding environment of zooplankton.

3.4 Fertilization is mainly based on the application of inorganic fertilizers containing nitrogen, phosphorus and other elements.

4 Management after freezing

4.1 For snow removal, the pond should try to keep 2/3 of the clear ice to maintain the transparency under the ice

4.2 Remove excessive black ice and dust on the water surface

4.3 Regularly and irregularly detect the dissolved oxygen under ice and take the following measures according to the dissolved oxygen situation:

Low dissolved oxygen: ① less phytoplankton and thin water: use hanging bag fertilization to increase the amount of phytoplankton; ② low transparency, phytoplankton cannot reproduce: find the reason to increase the transparency; ③ caused by the proliferation of zooplankton in water: use Chemicals kill zooplankton and then fertilize with appropriate amount of hanging bags.

4.4 When the dissolved oxygen is so low that the head floats, the aeration pumping method (because it is easy to cause frostbite, generally pumping water does not exceed 3 days) or adding new water, chemical oxygenation and other methods to relieve the floating head symptoms of fish first. Do other oxygenation treatments.

Dissolved oxygen is high: the illumination is good, and the phytoplankton multiply: ① reduce the transparency; ② kill some phytoplankton with chemical drugs; ③ raise water and aerate (generally no more than 3 days).

4.5 When the spring pond is about to be opened from freezing, some substances such as table salt or plant ash should be sprinkled on the ice surface to promote the early enlightenment of the ice surface.