Agrology (Jan 2020)
State of populations of non-migratory and introduced species of water bioresources in the water area of the upper part of the Dniprovs’ke water reservoir in the autumn period
Abstract
In the Dniprovs’ke (Zaporizh’ke) water reservoir in 2016–2019 works are being carried out introduction fish-bioameliorants (grass carp Ctenopharyngodon idella, silver carp Hypophthalmichthys molitrix and bighead carp Aristichthys nobilis, common carp Cyprinus сapriо). In the water area of the upper part of the reservoir the author’s supervision over the research work “Development of the project of reproductive and biomeliorative measures on the Dniprovs’ke water reservoir (upper part)” is carried out, including a comprehensive analysis of the state non-migratory and introduced species of water bioresources in the water area of the upper part of the Dniprovs’ke water reservoir. In autumn period the complex ichthyological investigations were performed on the upper part of the Dniprovs’ke water reservoir within city of Dnipro. The state of populations native and introduced fish species had investigated before wintering. The industrial fishing gears were used to catch watery bioresources – gill net with 38‒90 mm mesh size and small-mesh trawl with mesh size of 5 mm. The most significant accumulations of watery bioresources were recorded in the Mandrykivska bay of the water reservoir (silver carp, spotted silver carp, grass carp, common carp). Most species are represented by large-sized individuals (age group 5+ and above). The selectivity of large mesh nets was noted. The species composition of the catch differs by 100% in fishing gear with the mesh size of 75 mm and 80 mm. Most species introducents are withdrawn by means of nets with mesh size of 80 mm or more. By means of search trawl fishing with specialized small-size mesh trawl has been revealed significant industry fishing concentration bleak Alburnus alburnus and slightly black sea sardelle Clupeonella cultriventris on Mandrykivska bay. The catch by one trawl per 15 minutes was 132.62 kg (with a part of A. alburnus 94.2% by weight). The positive environmental and economic profitability of trawl fishing is noted. It is emphasized that the withdrawal of short-cycle species is the necessary measure of biological melioration in the Dniprovs’ke water reservoir. At the same time, the obtained biological production are withdrawn and the competitive relations of A. alburnus and C. cultriventris in the coastal zone with young commercial species, especially with fingerling are decreased. In the analysis the maximum allowable by-catch of fish of non-commercial measures in the bleak-ruff and sardelle of fishing gears did not exceed the indicator of 0.34% of the total mass of fish catch. It is proposed to more actively introduce catching with small-size mesh trawl in the water area of the upper part of the water reservoir for withdrawal bleak and black sea sardelle
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