The study presents materials on the status of aquatic biological resources and their habitat in the Dnieper River within the territory of the Russian and the Belarus. In the recent period, there has been hardly any complex fishery research in the upper reach of the river within the boundaries of the Smolensk Region due to the lack of commercial fishing; the same can be applied to the reach of the river within the Vitebsk Region in Belarus. The collection of materials and scientific and research accounting network surveys for monitoring the state of aquatic bioresources were carried out on the Dnieper River as part of the research in 2019 according to a preplanned grid of stations. When fishing for scientific research purposes, 20 net-stops of smooth frame nets were made in the Russian section, and 9 net-stops were made in the Belarusian section. In the Russian section of the Dnieper River, the species composition was 16 species of fish, and in the Belarusian section — 22 species. The main catch in the Russian section is roach 29% and chub 20%, in the Belarusian section bream — from 3 to 46%, roach — from 19 to 63% and gustera — from 1.8 to 33%, in a slightly smaller number of river perch (on average up to 10%). The share value of roach and guster tends to decrease from the upper to the lower areas, bream-on the contrary to increase, the value of perch is approximately equal in all areas. In the size structure of the caught fish species, there is a dynamic with a good reproductive potential.
Based on the materials of scientific monitoring at the Cherepetsky reservoir in the Tula region, the composition of the fish population at the present stage is given. The places of mass spawning and wintering of the main fish species were also identified. Wintering pits are located in the dam part of the reservoir, as well as downstream along the watershed dam. The places of mass spawning are located in the upper (river) part of the reservoir, as well as in the area of the village of Tsentralny. The materials were the results of hydro acoustic and grid surveys at the Cherepetsky reservoir in 2021. Ichthyological studies have not been carried out on this reservoir since 2013. According to the results of research surveys in 2021, with the use of the order of the set nets, a small variety of ichthyofauna was recorded — eight species of fish. According to the research results, a reduction in the species composition of fish was recorded. Natural fish productivity decreased from 140 kg/ha to 90 kg/ha. Reduction of natural fish productivity and absence of thermophilic fish species in catches (white carp, white and black cupids) most likely it is connected with the modernization of the Cherepetskaya GRES. Due to the lack of industrial fishing at the Cherepetsky reservoir, the exploitation of aquatic biological resources can be called irrational.To improve and develop the water body, it is recommended to carry out reclamation measures, the introduction of herbivorous (white and black Amur) and predatory fish (pike) and their protection.
In the paper, preliminary results of hydrochemical, hydrobiological, parasitological and ichthyological investigations have been given, carried out on waters of the Lake Senezh in 2020 and compared with analogous works for 2004–2006. The ecosystem of the given water object is extremely understudied. In the size structure of fish species, caught in 2020, dynamics of a good reproduction potential could be noted. The condition factor of all fish species is very high. One can see a significant prevalence of females over males, excepting bream, in all fish groups studied. The water object investigated showed the 2,8 times MPC increase for iron in fish farming water bodies. Concentration of toxic elements in water samples and bottom sediments did not increase MPC for all other indices. The bacteriological water analysis showed insignificant increase of bacterial contamination at the area of the investigation station 6 only, what is most likely of the anthropogenic nature and is being a result of the littoral lake zone pollution. Parasitological analysis of the Senezh lake fishes indicates of o high level of their invasion. 11 parasites species were found in 3 fish species investigated, which were represented by 73% of trematodes at the metacercaria and maritas stage. The fish ergasiles problem, existed in this water body since 2005 and up to-date, continues. In zanders gills, parasitic Ergasilus sieboldin were found. The given work would be interesting for investigators who will study the Senezh lake as well as other water bodies of the Moscow area.
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