Состояние кормовой базы бентосоядных рыб малого водоема на водосборе Онежского озера (Республика Карелия)

Abstract

Knowledge of the conditions of fish existence, one of the elements of which are the conditions of their fattening, allows us to determine the ways of rational use of fish production resources of the reservoir. The research was carried out by means of complex expedition observations in the summer-autumn period of 2017-2021 in the catchment area of Lake Onega (Lake Munozero, Republic of Karelia). The main criterion for assessing the productivity of reservoir is the indicator of the average biomass of macrozoobenthos. For Lake Munozero, it is equal to 3.6 g/m2 in the littoral zone, and 2.73 in the deep-water part. The average number of bottom organisms reaches 2.73 thousand specimens/m2 in the coastal zone of the reservoir, 1.14 thousand specimens/m2 in the profundal. Gastropods (34.9%) and equal–legged crayfish (22.4%) play a significant role in the composition of the biomass of the coastal zone of the lake. The remaining groups of macrozoobenthos are inferior to Gastropoda and Isopoda. Thus, larvae of large-winged insects make up 12.5% of the total biomass, and larvae of chironomids – 10.7%. Representatives of other groups of aquatic invertebrates: small-scale worms, beetles, mayflies, etc. – in the feed supply, they have practically no value and account for less than 6% of benthos biomass. In the deep-water part of the reservoir, the value of relict crustaceans in the macrozoobenthos should be noted in terms of food. Amphipods in terms of biomass 2.7 g/m2 (98%), with a population of 1 thousand individuals/m2 (89.5% of the total number of macrozoobenthos) significantly exceed all the present groups of benthic fauna, which forms the basis of the food base for the ichthyofauna of Profundal. The main importance in the taxonomic composition of the macrozoobenthos of the reservoir are aquatic insect larvae. Quantitatively, among all groups of zoobenthos, the larvae of chironomids or bell mosquitoes (family Chironomidae) dominate, which are not only widespread in the lake, but at the same time achieve a fairly large qualitative diversity. The data obtained can be used to assess fish stocks in Lake Munozero.