Influence of fish farming on the chemical composition of Lake Veljo water in 2015-2021

Abstract

Lake Velie is one of the largest reservoirs in the Novgorod region. It is part of the Valdai National Park and is located on the Valdai Moraine Ridge. However, environmental risks caused by pollution of the aquatic environment in areas where commercial aquaculture is grown, as well as the negative impact of fishery activities on the environment, can become an obstacle to further use of the lake water area for fishery purposes. Summarizing the data obtained, we can state the following: within a radius of 100 meters from the cages, the chemical composition of the water in the column is practically the same as in the central part of the lake.
The dispersion of the introduced substance obtained, both empirically and experimentally, corresponds to 50 m. At a distance of 50 m from the cages, water quality class 3 (moderately polluted). However, in a 10-meter zone, the water acquires the characteristic contaminated. In this part of the studied water area, the normative indicators for the content of biogenic substances on the surface and at the bottom are exceeded, and in the near -bottom horizon the numerical indicators are slightly higher than at the surface. This is most likely due to the accumulation of excessively introduced artificial feeds in the bottom horizon. Even with a favorable temperature and oxygen regime of the reservoir, such a situation does not contribute to the cultivation of healthy marketable fish. And the lack of comprehensive monitoring studies may leave unnoticed the prerequisites for the deterioration of water quality in Lake Velje.