«Let's make holes – save fish from freezing!»

Severe frosts contribute to the formation of an ice crust on the surface of a water body, blocking access of atmospheric air and oxygen, which can be accompanied by mass fish kills.
In some cases, winter fish kill can be caused by the presence of a large amount of humic substances and ferrous oxide in the water, the oxidation of which is accompanied by a decrease in dissolved oxygen in the water.

Among the effective measures to prevent winter fish kills is the creation of ice holes in water bodies prone to fish kill phenomena. The number of ice holes depends on the area of the water body and averages 3-5 pcs./ha. Ice holes should be located in the center of the water body and along its perimeter, where the depth of the unfrozen layer is 50-60 cm. To prevent ice holes from freezing, it is necessary to install sheaves made of reeds, cattails, and other hollow "breathing" plants in them, or to hang bags of salt in such ice holes at a rate of 5 kg/bag. Technical salt, which is used for cleaning boilers in boiler rooms, can be recommended as salt.

In order to prevent winter fish kills and avoid fish mortality, starting from February 2024, on reserve water bodies and those prone to fish kill phenomena, the Ministry of Natural Resources is initiating an environmental campaign "Let's make holes - let's save fish from fish kill!".