Attention! Fish kills!

Like other animals, fish cannot live without oxygen. Water is oxygenated in two ways: from the surrounding air and through the life activities of green plants. A fish kill can occur as a result of a lack or complete absence of oxygen in the water, which is necessary for fish life. If the amount of oxygen in the water decreases sharply, fish become agitated and often die.

In winter, under the ice cover, a negative oxygen balance is established, i.e., the consumption of oxygen for oxidation processes is higher than its intake from the atmosphere or as a result of photosynthetic activity. In shallow lakes, in the absence of flow, the oxygen regime is usually very strained, especially at the end of winter.

Depending on the duration and stability of the ice cover, the water volume, and the stocking density of fish, in some winters fish die completely, while in others only those most sensitive to oxygen deficiency perish. Sharp fluctuations in water level can cause great harm to overwintering fish. During the winter period, a sharp fluctuation in water level can lead to fish being crushed by ice in the coastal zone of the reservoir, and the fish will die.

Territorial bodies of the Ministry of Natural Resources and Environmental Protection form, maintain, and annually update databases with lists of water bodies where fish kills may occur. In addition, in cooperation with the Republican Center for Analytical Control in the Field of Environmental Protection, water bodies are surveyed to identify factors that can lead to fish kills. Water bodies are surveyed at least once every 15 days from December 15 to April 1.

In accordance with the Rules for Fishery Management, approved by Decree of the President of the Republic of Belarus dated July 21, 2021 No. 284, the lessees/users of fishing grounds (in leased/gratuitously used fishing grounds) and local executive and administrative bodies (in fishing grounds of the reserve fund) are responsible for organizing and carrying out measures to prevent fish kills.

The most effective measures to increase the concentration of dissolved oxygen are:

— making ice holes (to prevent ice holes from freezing: 1. Sheaves made of reeds, cattails, and other hollow plants are installed; 2. Bags with technical salt are hung). The number of ice holes depends on the area of the water body and averages 3-5 pieces/ha;

— liming. Liming promotes the decomposition and accelerated mineralization of organic matter, as well as improves gas exchange; it neutralizes the acidic reaction of water. Unslaked lime is applied to the water at a rate of 1-2 cwt/ha. When using slaked lime or ground limestone, the application rates increase by 1.3 and 1.8 times, respectively.

It should also be noted that in the event of pre-suffocation or suffocation phenomena occurring in fishing grounds, confirmed by hydrochemical research data conducted by accredited laboratories, the procedure and conditions for fishing shall be determined by district executive committees in agreement with the territorial bodies of the Ministry of Natural Resources and Environmental Protection and inter-district inspectorates for the protection of fauna and flora of the State Inspectorate for the Protection of Fauna and Flora under the President of the Republic of Belarus.