The article presents the results of a study of phenotypic characteristics in the population of Lin SPU "Isabelino". Comparison of some morphometric indicators of repair herd of tench with archival data is carried out.

As a result of the study of the content of total protein, cholesterol and glucose in the blood serum in underyearlings of the selection carp, changes in the physiological and biochemical parameters of blood serum were established depending on the growing conditions, due to different densities of stocking.

As a result of a study of the content of total protein, cholesterol and glucose in the blood  serum  of  underyearlings  and  yearlings  of  two-breed  carp  crosses,  changes  in  the physiological   and   biochemical   parameters   in   yearlings   compared   to   underyearlings   were established.  The  advantages  of  the  complex  of  physiological  and  biochemical  indicators  of individual crosses are noted.

The formation of the tenth generation of the Amur carp of the Khanka population has begun in Belarus. The article presents comparative data on the fertility of females, as well as the survival rate of the Amur carp eggs from the Belarusian collection population and its hybrids obtained from crossing with milk imported from Russia.

DNA identification techniques confirmed the species purity in the Beluga (Huso huso (Linnaeus, 1758) replacement broodstock of Beloozerskoye Branch, OJSC “Experimental Fish Farm “Selets”. mtDNA D-loop analysis established the Caspian population belonging of the Beluga raised on the fish farm. A lower level of genetic diversity was established in the Beluga stock of the Belarusian farm as compared to the Beluga from the sturgeon farms of the Russian Federation. Analysis of morphometric parameters and an ultrasound scan showed that housing conditions of the Beluga breeding stock on the fish farm “Selets” should be improved. It was established that 69.5% of the Beluga stock raised on the farm is represented by females.

The possibility of using starch production of the wastes fertilize fish ponds has been studied. It is shown that in terms of their chemical composition and the effect on fodder zooplankton for fish, potato pulp can be used as an organic fertilizer. The optimal single doses of pulp making application in ponds was determend.

One-time rats for the use of potato pulp were determined for ponds to increase their productivity. It was shown that a single application of pulp at the rate of 2-4 t/ha led to increase  total  and  natural  fish  productivity  while  reducing  the  cost  of  fish  feed  and  mineral fertilizers.

The characteristic of agrochemical indicators of discharge channels sediments of fishponds, selected from the most typical underlying soils of fishery enterprises of the republic,  is  given.  The  provision  of  discharge  channels  sediments  with  macro -  and microelements available for plants, the correspondence of agrochemical parameters to the gradations used for soils, were estimated. The reserves of biogenic elements in sediments were calculated.

It was found that the discharge channels sediments of the ponds washed up from peat bottom sediments are highly supplied with mineral nutrition elements, organic matter and can be used as an additive for the crop cultivation.

Zooplankton development rates of three fish ponds were studied. Based on determined average season values, the feeding degree and the level of ponds trophiness were established. According to their bioproductivity, one pond is mesotrophic and has secondary level of feeding degree, two ponds are oligotrophic and have low level of feeding degree.

Studies of water samples were carried out in ponds of fish farms and separate blooming reservoirs aimed to identify quantitative and qualitative characteristics of phytoplankton development in them. The content of chlorophyll-a in sampled water bodies varied from 3 to 425 μg/l, the content of seston varied slightly less – from 2 to 210 mg/l. In all the samples, a low proportion of pheopigments was noted, constituting in average 18%, the specific chlorophyll-a content in seston was close to 0,3%.  It has been shown that pigment indices can be used to characterize the important structural parameters of phytoplankton in ponds. A close interrelation was found between the index E450/E480  and the share of cyanobacteria in the total phytoplankton biomass (r=-0,81), and, on the contrary, there was the positive correlation of this index with the share of green algae (r=0,77).

The state of commercial fishing and fish resources of natural reservoirs and watercourses of the Republic of Belarus has been analyzed. The information on the lease of fishing grounds and the dynamics of commercial fish catch is presented.

The values of fish stocks by categories of commercial grounds and possible catch volumes in modern condition have been clarified. The reasons for the decline in commercial fish stocks are analyzed.

Some hydrological indicators (hydrochemical regime, composition and degree of development of hydrobiont communities) of the state of the Viliya river section in the construction area of the Belarusian nuclear power plant, which can serve as parameters for monitoring the anthropogenic impact on the river ecosystem, are considered.

Methods of preparing water bodies for their transfer to the regime of grazing fish.

The European  eel is species of the native fish fauna of Belarus. Natural eel recruitment to the part of its trophic areal in Belarus is significantly limited for reasons outside of country’s control. Maintenance of natural eel population is only possible by means of re-stocking with elvers. The Republic of Belarus guarantees the pass to the transit water courses not less than 40%  of  migrating  eel  in  accordance  with  the  EU  Council  Regulation  dated  18.09.2007  № 1100/2007. Maintaining a ban on the supply of the stocking material to the Republic of Belarus may result in the fact that the global population of the European eel will lose part of its brood-fishes migrating for spawning from this fishing area.

The article presents data about the identification of tubenose gobies of the genus Proterorhinus in Belarus. Study based on cyt b gene analysis showed that Proterorhinus semilunaris (Heckel, 1837) established on the territory of Belarus, and was previously identified as Proterorhinus marmoratus (Pallas, 1814).

It was shown that on the Belorussian part of the central invasive corridor (Pripyat river – Pina river – Dnieper-Bug channel – Mukhavets river), alien species of the Gobiidae family (monkey goby, racer goby and tubenose goby) mainly inhabit in biotopes with a slow course and prefer places without shell rock.  In relation to the degree of soil siltation and overgrowth by higher aquatic vegetation in the habitats, the opposite positions are occupied by the tubenose goby and the monkey goby. The first of them prefers the most overgrown and silted biotopes, the second – the least overgrown and silted. Racer goby takes an intermediate position.

In recent decades, the problem of spreading and establishment of alien fish species has become increasingly significant worldwide. The main rivers of Belarus belong to the Central European invasion corridor that connects the basins of the Black and Baltic Seas, and plays important role in distributions of non-native species from Ponto-Caspian region to the European waterbodies. It is assumed that in the near future invasions will only increase. The article presents data about the genetic variability of alien and native populations of the monkey goby (Neogobius fluviatilis (Pallas, 1814)), obtained from the analysis of the COI gene of 28 specimens of this species. Low genetic variability, low haplotype and nucleotide diversity are shown for both alien and native populations of the monkey goby.

An assessment of the quantitative development, biodiversity and equitability of phytoplankton communities in the lakes of Sarochanskaya group in the Viliya river basin has been conducted in spring and summer 2009. A comparative assessment of these indicators is given for the lakes of different depths: shallow, medium-deep and deep. The lakes show a great variety of phytoplankton  communities  and  their  polydominance.  The level  of  quantitative  development  and species diversity of phytoplankton characterize the studied waterbodies as meso- and eutrophic ecosystems with a high self-purification potential providing a sufficiently high water quality.

According to the results of water samples collected in spring (May) and summer (August) in 12 lakes of the Sarochanskaya group in the basin of the Viliya river, taxonomic composition of phytoplankton, its species richness, abundance of species and intraspecific taxa in divisions and classes of algae in each of the lakes and dominant complexes of species are given. In most lakes diatoms dominated in spring; in some lakes, golden algae were second. Some of algae are rare species not only for Belarus, but also for other countries. In summer, in lakes, where an increase in the species richness of phytoplankton was noted, compared with spring, it was determined mainly by representatives of green algae. In lakes, where there was a decrease in species richness, this was due to a decrease in the number of diatoms. In both summer and spring, the phytoplankton communities of most of the studied lakes are polydominant. The dominance of representatives of golden algae, along with diatoms, distinguishes the studied lakes among clean, productive waterbodies of interest for further scientific research.

The   paper   analyzes   the  main   indicators   of   the   application   of  the   drug "Diplocidum", allowing to assess the feasibility of its use in industrial conditions - economic and therapeutic efficiency. The results of the analysis indicate that the drug "Diplocidum" is effective both for treatment (used by group feeding and the method of therapeutic baths) and for the prevention (used by processing fish in ponds) of diplostomosis in fish.

The article outlines an alternative option for holding virtual exhibitions, due to the problems with holding classic exhibitions during a pandemic. The features of the organization and implementation of ideas at virtual exhibitions are presented, the advantages and disadvantages are shown.

The article describes the conduct of patent research at the Institute of Fisheries. Relevant materials related to directions, stages and results of patent research in research and development are presented.