Biological resources of Lake Kroshnozero (North-West of Russia)

Abstract

A comprehensive analysis of plankton and benthic communities, composition, structure and quantitative characteristics indicate that the ecosystem of Lake Kroshnozero has a eutrophic status or a transitional one between the β-mesotrophic and α-eutrophic. Plankton communities are in a stable state and provide a sustainable food base for planktivores fishes. A slight decrease in the quantitative indicators of benthos is possibly due to the methodological features of sampling and the underestimation of littoral communities. The composition and structure of benthic communities have been preserved since previous studies in the 50-90s of the last century. The ichthyofauna of Kroshnozero includes 13 fish species. Whitefish, zander, and vendace are fish of commercial importance. Fish of secondary importance are bream, perch, ruff, roach, and pike. Fish such as bleak, grayling sculpin, and burbot are relatively rare and do not serve as objects of fishing. Model calculations of fish productivity of planktivores, benthophages and predatory fish, taking into account losses to 2.3 kcal/m2 per season or 22.6 kg/ha. The average modelled ichthyomass is 4.6 kg/ha. Possible catches are one third of fish productivity equal to 7.5 kg/ha. To improve the quality and quantity of commercial stocks, recommendations are given to preserve the conditions for the reproduction and growth of valuable fish.