Assessment of fish productivity of two small Karelian lakes using a balance model

There are over 60,000 lakes in the Republic of Karelia (Northwest Russia). In recent years, this region has been increasingly used for tourism and recreation. The development of amateur and sport fishing increases the relevance of rational use of the bioresources of the lakes in this region. Due to the unique features of their natural potential, lakes Kroshnozero and Urozero are a favorite vacation spot for local residents, centers of attraction for tourists, and fishing enthusiasts. To assess the fish productivity of two Karelian lakes, Kroshnozero and Urozero, the mass- balance model of V.V. Bulyon was used. This model reflects the most general patterns of distribution of organic matter and energy in trophic networks of a lake ecosystem. The model was verified using hydrochemical and hydrobiological parameters of lakes (phytoplankton, zooplankton, and macrozoobenthos biomass) obtained in field conditions over the past decade. Comparison of empirical data with model calculations showed good convergence. It was shown that the adequacy of the model in describing lake processes allows its use as a tool for assessing fish productivity in various reservoirs.