The features of the natural fish productivity formation of a shallow reservoir free of ichthyofauna on the western slope of the Volga upland within Penza region

Background. The development of “artisanal” aquaculture, fish farming, fish cultivation in reservoirs of complex purpose is given great importance, both at the global level, in the Russian Federation and in Penza region. This was facilitated by the presence of numerous ponds and small reservoirs of complex purpose, dispersed throughout the region. However, despite the high growth rates of fish production in the region as a whole, the fishproductivity of the reservoirs used remains quite low. To develop methods for optimal cultivation of aquaculture facilities and rational use of aquatic biological resources, it is necessary to know the real picture of the productivity of the forage base of the reservoirs of the region, taking into account modern climatic changes, since the current standards of fish farming for Penza region are clearly outdated. For these purposes, we have chosen an artificial reservoir that is not subject to direct anthropogenic impact, without representatives of the ichthyofauna. The purpose of this work is to determine the real natural fish productivity in a shallow reservoir on the basis of a natural food base for fish free from representatives of the ichthyofauna. Materials and methods.General observations of the shallow reservoir and its aquatic inhabitants were constantly carried out in 2014–2021. Sampling of zooplankton, zoobenthos, necton, neuston, macrophytes was carried out in the non-freezing period from April to November. The samples were processed in accordance with generally accepted methods. Calculations of fish products were carried out using up-to-date data on P/V coefficients, feed coefficients for individual feed components (taking into account their digestibility). Which are used in scientific research and practical work to determine theconsequences of a negative impact on the state of aquatic biological resources and their habitat. Results.Fish production by the main components actively used by the local ichthyofauna (zooplankton, zoobenthos, necton, neuston) can reach 356–427 kg/ha in May–June. The total fish production, taking into account the potential components of the food base (phytoplankton, macrophytes) consumed by herbivorous cultivated fish, may amount to 427–502 kg/ha, respectively. For comparison, the average natural forage base of eutrophic reservoirs of the region with native ichthyofauna not used by fish for food in the summer period is 135.1 kg/ha, the average total productivity of the reservoir, taking into account thefish living in it, is 508 kg/ha. When carp is grown by one-year-olds, the real natural fish productivity of a shallow reservoir in this zone during the growing season of commercial fish can be 400–500 kg/ha. Conclusions.The results obtained in a shallow reservoir without representatives of the ichthyofauna in terms of natural fish productivity in the forage base in the considered zone indicate the possibility of achieving fish productivity at the level of 400–500 kg/ha during the seasonal period of pond fish cultivation, which is a higher indicator in comparison with the available data for Penza region and data on reservoirs of neighboring regions.