Current state of secondary commercial species populations in the Kremenchutskе reservoir

Goal. To determine and analyze the structural and quantitative parameters of secondary commercial species of the Kremenchug reservoir. Methodology. The data of commercial catches of the Kremenchug reservoir for 2009–2019 were used as primary materials. The methods generally accepted for ichthyological studies were used for the sampling and further analysis Findings. Commercial catches of native fish species belonging to the category of "secondary large species" (catfish, pike, asp, chub) in the Kremenchug reservoir in recent years show a tendency for an increase: in 2010-2014 their landing was at 78 tons, in 2015 - 104 tons, in 2016 - 107 tons, in 2017 - 134.9 tons. This increase was mainly (by 65%) ensured catfish, to a lesser extent (by 30%) by pike. In 2018, there was a significant decrease in landings in this category to 116.1 tons, in 2019 - again an increase to 140.7 tons. A similar trend was observed for the category of secondary small-sized species (perch, knife, rudd, tench): in 2010-2014 the catch did not exceed 66 tons, in 2015 - 104 tons, in 2016 - 107 tons, in 2017 - 97 tons. In recent years, the maximum catches of commercial native fish species belonging to this category were observed, e.g., 179.6 tons in 2018, 175.3 tons in 2019. Due to a low abundance of these species, both commercial and survey catches have a certain instability, while there is a lack of clear trends in the dynamics of structural and functional parameters of catches. The main factor that limits the statistics of this category is the organization of fishing and accounting of landed fish. Originality. For the first time, data on commercial catches of native fish species belonging to the category of "secondary large species" and "secondary small species" in the Kremenchug reservoir in recent years have been obtained and analyzed. Practical significance. The obtained results will be used for preparation of the fishing regime in the Kremenchug reservoir. Improving the level of organization of fishing and accounting of landed fish. Keywords: reservoir, secondary large species, secondary small species, commercial catch.

Structural-functional organization of littoral zooplankton community of the upper Kremenchug reservoir in the territory of Kaniv nature reserve

The analysis results of the structural-functional organization of littoral zooplankton community of the upper Kremenchug Reservoir in the territory of Kaniv Nature Reserve during the summer of 2015 are presented. Diversity of zooplankton was presented with 34 species: Monogononta rotifers, cladocerans, copepods. The rotatoria-cladoceran zooplankton complex dominated in the taxonomic composition. Zhakkara dominant index for the comparison of the dominant species complexes was used, and it was the low number of similarities within the various biotopes of the six research stations (J = 7,1-28,6). This can be explained by the formation of higher aquatic plants.This led to the formation of specific zooplankton groups in overgrown biotopes.The ecological spectrum of the different groups of the upper Kremenchug Reservoir littoral zooplankton in the summer was characterized by the predominance of the phytophilic groups: phytophilic – 18 species (53 % of all zooplankton species). Depending on the feeding type the largest part was made by the peaceful group – 73,3 % (25 species). Summer littoral zooplankton in quantitative terms was characterized by very low development in both biotopes. Its density varied within 4077± 2098 ind./m³ and biomass 0,07 ± 0,04 g/m for overgrown biotopes, and 4123 ± 3929 ind./m³ and 0,054 ± 0,038 g/m³ for freshwater ones. Among the quantitative indicators, the species of Copepoda dominated, what was associated with the development of their larval stages (Nauplia, Сalanoida juv., Cyclopoida juv.) in the summer period.