Fish, like other animals, cannot live without oxygen. Water is enriched with oxygen in two ways: from the surrounding air, thanks to wind and rain, and due to the vital activity of green plants. As a result of a lack or complete absence of oxygen in the water, which is necessary for the life of fish, fish kills may occur. Fish kills are the mass death of fish as a result of a decrease in the oxygen dissolved in the water. Winter fish kills are observed both as a result of a complete cessation of oxygen supply from the air, and a sharp limitation of the vital activity of plants under the ice. The establishment of a strong ice cover and the impossibility of contact between water and air (gas exchange) is the main factor that can cause a fish kill.
Frosty weather contributes to the formation of an ice shell on the surface of water bodies, blocking access to atmospheric air and oxygen, which can cause mass death of fish and their young.
The most effective measures to prevent winter fish kills include the following:
- adding lime to water bodies;
Liming promotes decomposition and accelerates mineralization of organic matter, as well as improves the gas regime, neutralizes the acidic reaction of water. Quicklime is added to the reservoir at the rate of 1 – 2 c/ha. When using slaked lime or ground limestone, the application rates increase, respectively, by 1.3 and 1.8 times.
- making ice holes in reservoirs;
The number of ice holes depends on the area of the reservoir and averages 3-5 pcs/ha. The ice holes should be located in the center of the reservoir and along its perimeter, where the depth of the non-freezing layer is 50-60 cm. To prevent the ice holes from freezing, it is necessary to install sheaves made of reeds, cattails and other hollow “breathing” plants in them or hang bags of salt in such holes at the rate of 5 kg/bag. Technical salt, which is used to clean boilers in boiler houses, can be recommended as salt.
- aeration of reservoirs.
Aeration is a process in which air is in close contact with water, by spraying water in the air or passing air bubbles through the water. Along with this, an aeration method is used that uses hydromechanical mixing of the water column.
If you have discovered a fish kill, you must inform:
- in leased or free-use fishing grounds – the State Inspectorate for the Protection of Fauna and Flora under the President of the Republic of Belarus, as well as tenants and users;
- in stock fund fishing grounds – the State Inspectorate for the Protection of Fauna and Flora under the President of the Republic of Belarus, the Ministry of Natural Resources and Environmental Protection and its territorial bodies, local executive and administrative bodies.
