Fish kills are mass deaths of fish resulting from a decrease in dissolved oxygen in the water.
The first signs of winter fish kills are the appearance of juvenile fish and other organisms in ice holes and openings. The water becomes cloudy and develops an unpleasant odour during this period. Amateur anglers who visit water bodies at this time can help the dying fish: several cut holes provide an additional amount of oxygen in the water.
The Lepel District Inspectorate of Natural Resources and Environmental Protection draws attention to the fact that, due to seasonal weather conditions and possible temperature drops to minus 15 degrees Celsius and below, with a stable ice cover on water bodies and watercourses that limits the supply of atmospheric oxygen to the water in some fishing grounds, especially in stagnant and landlocked water bodies with sapropel or other organic residues on their bottom, pre-kill and kill phenomena may be observed.
In order to prevent fish kill phenomena, the Lepel District Inspectorate of Natural Resources and Environmental Protection, as well as lessees and users of fishing grounds, are actively working to take measures to prevent winter fish kills.
The National Academy of Sciences of Belarus recommends the following to prevent winter fish kill phenomena:
1. Application of lime to water bodies prone to fish kills. Liming promotes the decomposition and accelerated mineralisation of organic matter, as well as improving the gas regime and neutralising the acidic reaction of the water. Unslaked lime is applied to the water body at a rate of 1-2 centners per hectare. When using slaked lime or ground limestone, the application rates are increased by 1.3 and 1.8 times, respectively.
2. Creation of ice holes in water bodies prone to fish kills. The number of ice holes depends on the area of the water body and averages 3-5 per hectare. Ice holes should be located in the centre and along the perimeter of the water body, where the depth of the unfrozen layer is 50-60 cm. To prevent the ice holes from freezing over, bundles made of reeds, cattails, and other hollow "breathing" plants should be installed in them.
3. Hanging bags of salt in such ice holes at a rate of 5 kg per bag. Technical salt, used for cleaning boilers in boiler rooms, can be recommended as the salt.