Overseas phenomena: causes and prevention

Fish kills are the death of fish and aquatic invertebrates due to a decrease in dissolved oxygen in the water. Fish kills can occur at any time of the year. In winter, they occur due to complications in the processes of oxygen transfer from the air, as well as due to the decomposition of organic matter.

Most often, such phenomena occur in shallow, stagnant or poorly flowing lakes with a high content of organic matter, as well as in small rivers.

Factors leading to fish kills include: temperature and gas regimes, water turbidity, aquatic vegetation overgrowth, hydrochemical parameters, etc.

The temperature regime seriously affects the solubility of oxygen in water. When high water temperatures are combined with abundant aquatic vegetation, the acid-base balance can be disrupted. In winter, the situation is complicated by the thick ice cover, prolonged air temperature drops to -15°C and below, and a stable snow cover.

Fish kills may not be observed over the entire area, but in one or more sections. And the species composition of losses can be uneven, as each species reacts differently to a decrease in dissolved oxygen in the water.

Sometimes, human economic activities also become the cause of fish kills. Pollution of water bodies as a result of, for example, untreated wastewater discharges leads to an increase in chemical reactions associated with oxygen consumption.

In winter, the main cause of fish kills is natural factors. Most of the country's reservoirs and watercourses are part of the so-called fishing grounds, where fishing is permitted. Some of them are leased for commercial fishing or for gratuitous use. The rest are part of the reserve fund.

The protection of fishing grounds in the reserve fund is carried out by local executive and administrative bodies or specially authorized legal entities. Measures to prevent fish kills and eliminate their consequences should be financed from local budgets. The same task is set for lessees and users of fishing grounds.

Even if fish kill has already begun, there is a chance to save most aquatic inhabitants, the main thing is to act promptly. For this purpose, responsible persons on lakes and rivers carry out water aeration, liming, snow removal, and arrange ice holes and borings. The number of ice holes depends on the area of the water body; they should be located in the center of the water body and along its perimeter. The assistance of the local population is very important in activities related to the prevention of fish kill phenomena.

We strongly urge all concerned citizens, especially fishermen, upon detecting signs of fish kill phenomena, to report to the regional units of the State Inspectorate or territorial bodies of the Ministry of Natural Resources and Environmental Protection.

For additional information or on cases of poaching, please contact the Verkhnedvinsk Inter-district Inspectorate for the Protection of Fauna and Flora at the following address: Verkhnedvinsk, Sovetskaya St. 193/2 or by calling the hotline at 6 17 23.