The results of fish production in aquaculture and the catch of fishing objects in fishing grounds for 2022 are presented and analyzed. It is noted that aquaculture (pond and industrial) remains the main source of food and technical products in the inland waters of the country, while fishing is an additional direction of production and is aimed at using available natural resources. It is noted that 15 specialized pond fish farms, 380 tenants of ponds and watered quarries used for fish farming, as well as 11 business entities engaged in industrial fish farming were engaged in fish farming (commercial and recreational) during the period under review. In addition, 76 tenants and users of fishing grounds are engaged in commercial fishing and/or the organization of paid amateur fishing, 11 business entities are harvesting commercial invertebrates — freshwater crayfish. Total fish production in 2022 it amounted to 12.66 thousand tons, including commercial catch (production of commercial products) — 8,133 thousand tons. The overwhelming volume of production of commercial fish falls on aquaculture — 7,637 thousand tons. 

A brief historical background is given on the directions and results of the work of the laboratory of fish farming and fisheries as the infrastructure of the fishing industry of the Republic of Belarus develops. On the territory of Belarus there are about 20.8 thousand rivers, 10.8 thousand lakes, and more than 140 reservoirs, the country occupies a leading position in terms of provision of surface water resources on the European continent. The main task of scientific research conducted by the laboratory is the conservation of fish resources and their habitat, regulation of exploitation and increase in fish productivity.
The results of the scientific activity of the laboratory are presented depending on the priorities at each historical stage. Scientifically substantiated possibilities of bringing fishery products up to 30–40 kg/ha and more instead of 8–10 kg/ha with natural productivity, growth of commercial fish products up to 200–300 kg/ ha using methods of pasture fish farming are shown. The result of scientific work on the enrichment of the qualitative composition of catches is an increase in the share of valuable and economically important fish species in the total commercial catch up to 87 % with a stable composition of more than 50 %, while at the turn of the 70–80s this figure did not exceed 35 %. The developed system of classification of fishing grounds is the basis of modern principles of exploitation of fish resources and has been recognized in the form of a number of regulations and regulations in the field of fishing.
The prospects for the work of the unit for the next five years are displayed, aimed at ecological research of natural and artificial reservoirs for the purpose of their rehabilitation and further fisheries use, research on the sustainable use of aquatic biological resources of protected areas in order to develop plans for their management, monitoring the state of the fishing resource base, testing technologies for the artificial reproduction of a number of valuable native fish species for the purpose of economic use and restoration/maintenance of natural populations, development of regulatory and technological documentation in the field of fishing, testing technologies for creating farms for recreational fishing using elements of fish farming.

The article describes the directions of research of the laboratory of hydrobiology and hydrochemistry in the historical perspective and at the present time. The main results of scientific research and achievements of the laboratory are represented. Promising areas of research that are of scientific interest in the near future are outlined.

The paper presents the results of the directions of ichthyopathological research in fish farms and natural reservoirs, which are carried out by researchers of the Laboratory of Fish Diseases at the present stage. The intensification of fish farming implies compliance with preventive measures to prevent and control diseases of hydrobionts and their pathogens, as well as the consequences of their negative impact. It is important to use a science-based approach, including monitoring studies, current diagnostic studies, their analysis and forecast of the current situation in the framework of risk management in the fish farming and fishing industry, as well as taking, if necessary, adequate actions, including the application of general economic measures and special funds.

The article presents the results of the Institute’s research in the field of feed production over the past 30 years and the directions in which these studies are conducted. The main direction of research is research on reducing the cost of compound feeds by searching for new domestic non-traditional sources of raw materials for their production. The second area of research is aimed at reducing the unit costs of feeding fish. All conducted scientific research is aimed at making compound feeds highly effective, reducing their price, and obtaining fish products at an affordable price for the consumer.

The article presents an overview of the Institute’s long-term research in the field of breeding and breeding work with carp for the entire period of work of the Institute’s staff in this direction: the beginning of the creation of breeding herds, breeding work on the breeding of Belarusian carp breeds, the creation of a collection herd of foreign breeds, the study of the effect of heterosis in interbreed, intrabreed and intraspecific crosses. The main directions of the laboratory’s research at the present stage are highlighted. Further breeding and breeding work involves the breeding of new breeds that meet the growth of consumer demands and contribute to improving the efficiency and competitiveness of industrial fish farming.

The article is an analytical review of the activities of the pond fish farming laboratory (hereinafter — pond and industrial) from the moment of its foundation to the present, a description of the tasks solved during the research work that had a noticeable impact on the aquaculture of Belarus, a brief description of the projects currently being carried out, as well as promising areas of activity.

As a result of the analysis of fish-breeding indicators of the cultivation of two-year-old crosses obtained from crossing the Amur carp with collection lines of carp of different breed affiliation, separate combinations of crosses characterized by the effect of heterosis and increased specific combinational ability were identified. All combinations have an advantage in one or another fish-breeding indicators. When using three methods for assessing the manifestation of the heterosis effect, crosses showing a tendency to increase their productivity were established: Lakhvin scaly x Amur carp; reciprocal combinations of Amur carp with German and Yugoslav carp.

The article presents an overview of the fish breeding, reproductive genetic, biochemical, morphological and other characteristics and qualities of the German carp bred in the Republic of Belarus and their changes since the beginning of its breeding in 1991.

As a result of the analysis of the wintering indicators of yearlings of crosses obtained from crossing the Amur carp of the ninth generation with collection lines of carp of Belarusian and foreign selection, which are part of the collection herd of the selection and breeding area «Isobelino», calculated crosses were determined, characterized by the effect of heterosis and features of specific combination characteristics: in 8 combinations of 11 were noted as an advantage in fish farming indicators.For the analysis, three methods were used to assess the manifestation of the heterosis effect (ranking, determining the indices of heterosis and combination ability).
Crosses have been established that show a tendency to increase their winter hardiness. According to body weight, the advantages of crosses sazan x Lakhvinsky scaly carp, sazan x carp Fresinet, German carp x sazan; the crosses of sazan x carp Lakhvinsky scaly lost weight less. Carp German x sazan, Three prim (Isobelinsky) x sazan, carp Yugoslavsky x sazan crosses were characterized by increased survival. In terms of the sum of indicators of body weight loss and survival, the Three prim x sazan cross was characterized by a significant advantage, as well as reciprocal combinations of carp with German carp. However, only the cross of Three prim (branch of Isobelinsky carp breed) with wild Amur carp (sazan) had an advantage both in terms of the level of body weight loss, and in terms of survival (34.1 g, 0.9 %, 90.0 %, respectively).

The article presents data on the biochemical composition (dry matter content, moisture, fat, protein and minerals) in the muscles of two-yearold crosses of the Amur sazan with carp of different breeds from a collection herd formed in Belarus. Combinations have been established that are characterized by increased levels of dry matter, fat, protein compared with the average value of the indicators of all crosses, as well as their parental forms (Amur carp and carp) grown under the same conditions.

A study was made of the exterior indicators of reciprocal crosses obtained from the wild Amur carp, originating from the Khankai population, with carp lines of different breeds of Belarusian and foreign selection, which are included in the collection herd of the Isobelino selection and breeding plot. As a result of studying the indicators of the physique of sazan with carp crosses, combinations were identified that are characterized by increased values of the coefficient of fatness, broad and high back, which are valuable for growing them in pond farms. Hybrid offspring has an exterior intermediate between the original parental forms: crosses between the wild Amur carp and carp of Belorussian and European breeds are characterized by increased indicators of fatness and high back compared to the wild Amur carp, but it’s are inferior to breeds selected for an increase in high back. Reciprocal combinations of sazan and Lakhvin carp, sazan x Tremlyansky scaly carp, sazan x German carp, three prim carp x sazan are characterized by advantages in terms of a complex of exterior features. 

The effect of the microbial preparation «Bioprud» on the formation of the natural fооd base and fish productivity was studied at different terms of introduction on bottom sediments of experimental ponds. The preparation’s positive effect on the outflow of nutrients from bottom sediments as well as indices of natural and total fish productivity of feeding ponds was shown. The greatest increase in marketable fish was noted in the group of ponds, where bottom sediments were treated with the preparation since the autumn of the previous year.

The effectiveness of 2 types of composts for the fish industry was assessed on the basis of main communities of living organism’s development and the yield of fish products in ponds. It was established that their use reduces the cost of feeding fish and expensive fertilizers, and also makes it possible to fertilize the categories of ponds where the use of manure is prohibited.
Most of the standardized parameters when adding compost mixtures did not exceed the established standards.
In the variants where the greatest development of phytoplankton and zooplankton communities was achieved, biomass parameters exceeded the controls by 2–3 times. When using compost mixtures in ponds, the dominance of green algae (21,6–73,8 %) and copepodit stages of copepods (47,3–53,6 %) was noted, among macrozoobenthos — chironomid larvae.
The introduction of the developed biocompost mixtures into the ponds made it possible to increase the natural fish productivity by 41,1–60,0 % compared to the control not fertilized ponds, as well as to increase the yield of fish production by 25,5–96,8 %.

The article provides a justification for the need for research aimed at increasing the production efficiency of grass carp planting material and, consequently, increasing its production in the conditions of pond aquaculture in Belarus. A brief analysis of the existing problems in this area is given and the main ways to solve them are identified. Preliminary results of research in the chosen direction are presented, in particular, materials on quantitative and qualitative characteristics of feeding of grass carp juveniles at various stages of cultivation, fish-breeding results obtained during research, data on the biochemical composition of fingerlings with different variants of growing in monoculture at the end of the growing season. A comparative analysis of the results of wintering of the grass carp, grown in various conditions, is also given, in particular, the survival rate, biochemical and physiological indicators of the obtained yearlings of the grass carp are evaluated.
In the course of the research, the prospects of the chosen research direction, as well as the methods used to increase the efficiency of obtaining grass carp seeds and its wintering in the conditions of pond aquaculture of the republic were established. It has been established that the rearing of the larva of the grass carp with the combined use of live and concentrated feeds is an effective method of increasing survival at the initial stages of growing juveniles and provides high production indicators — survival and growth rate. Significant differences have been established in the feeding characteristics of the juvenile grass carp compared with other pond carp fish after an approximately 40-day life period. It has been revealed that zooplankton organisms, which are the target objects for stimulating the development of the pond feeding base, form the basis of feeding of the young grass carp only for 20 (in the case of an undergrown larva) — 35 days of keeping in ponds. During such a period, only manure used in full dose before flooding ponds and used by zooplankton as a carbon source almost directly can give a pronounced effect, the use of mineral fertilizers is ineffective. When growing grass carp in a monoculture, high fish productivity indicators (348–361 kg/ha) were achieved in all variants. In the variants stocked with an undergrown larva, the average individual weight of fingerlings was higher than in the variants with an ungrown one. The survival rate in the variant with an untamed larva was lower. The fingerling obtained from an undergrown larva had, at the trend level, a more favorable biochemical composition for wintering, since it accumulated more nutrients with a higher average individual weight (25,8 g). The yearling obtained from the undergrown larva did not show a noticeable difference with the yearling from the ungrown larva in survival during wintering. Survival rates were 80 and 78 %.

The article presents data on the characteristics of the physiological state of black Amur fingerlings before wintering. To do this, the biochemical composition of the body and hematological parameters of black cupid fingerlings were studied. It was found that basically all the studied indicators of the biochemical composition of the fish body were within the recommended values for winter-hardy fingerlings and were characterized by a low level of variability with coefficients of variation of less than 12.65 %. It was shown that the fingerlings of the black Amur before wintering had an increased protein content in the dry matter, which averaged 13.96 %, with very low variability on this basis — 0.27 %. The moisture and dry matter content in the body of black Amur fingerlings corresponded to the recommended amount of these components before wintering and averaged 73.34 % and 26.66 %, respectively, with a sufficiently low variability of 0.54 % and 1.49 %, respectively. It was found that the hematological parameters of the black Amur fingerlings before wintering were in the age norm, which indicates their satisfactory physiological condition. The average concentration of hemoglobin in black Amur fingerlings was 48.8 g/l, ESR — 4.8 mm/hour, erythrocytes — 0.6 million/ml, leukocytes — 19.4 thousand/ml. In black cupid, the leukogram has a pronounced lymphoid character. The leukocyte formula was dominated by agranulocytes, their average content was 64.8 % characteristic of this age (lymphocytes — 54.3 %, monocytes — 10.5 %, granulocytes — 35.2 %).

The conditions of pre-spawning maintenance of black Amur producers (hydrochemical regime of water in a warm channel at the place of installation of cages, the level of flow), biotechnology of reproduction of black amur, biological features of reproductive processes and production characteristics were studied. In the department «Beloozersk» of ОJSC «Experimental fish farm «Selets» of the Brest region of the Republic of Belarus, the level of flow, temperature and hydrochemical regime of water in the channel, at the installation site of cages with producers of black amur fully met the fishbreeding requirements. The water flow velocity in the warm discharge channel of the Berezovskaya hydroelectric power plant was at an optimal level and was 0.50 m/sec, the pH of the medium in the pre-spawning period was also at a stable level of 8.10–8.30, the water temperature was in the range of 10–23°C.
The values of permanganate oxidizability 11.70–13.10 mg O/l, carbon dioxide concentrations 2.80–3.00 mg/l, phosphate content 0.02–0.12 mg/l, iron 0.04–0.17 mg/l, nitrites 0.008–0.101 mg/l and ammonium nitrogen 0.01–0.18 mg/l did not exceed the permissible values. The females had rather high production characteristics. The working fecundity was at the level of 214.87–650.3 thousand eggs, which significantly exceeds the norm for a specific weight category. The relative fecundity was quite high from 15.92 to 60.78 thousand eggs, which is a good result, since the average relative fecundity of black Amur females of different generations in the southern regions of Russia in the 5–6 fish breeding zone is from 30 to 70 thousand eggs. Sufficiently high absolute and relative fecundity of females indicate that the conditions of keeping in the pre-spawning period (temperature, chemical composition of water, flow rate) were favorable for the growth of fish and the preparation of producers for spawning.

The expediency of using hybrids in aquaculture is associated with the possibility of combining the desirable qualities of the original species in them. To date, a large number of interspecific hybrids of sturgeon fish have been studied and tested in industrial aquaculture farms, but 3 breeds bred on the basis of crosses of beluga with sterlet (bester) were the first registered by the State Commission of the Russian Federation of Breeding Achievements in 2000 under the names «Burtsevskaya», «Vnirovskaya» and «Aksaiskaya». The cultivation of reciprocal forms of the Burtsevskaya breed bester (beluga × sterlet; sterlet × beluga) was started in the ponds of the Saratov region, continued in the Rostov region until the 4th generation. The 5th generation was entirely grown in the pools of the RAS near Moscow. The purpose of this study was to compare the producers of the bester «Burtsevskaya» of the 3rd and 5th generations of breeding to determine the stability of the breed. The assessment was carried out by comparing different generations in terms of the value of exterior indicators: indices of progenity, body thickness, body girth, fatness coefficient (KF) and economically valuable traits: female productivity, viability of offspring and the level of embryonic disorders in early ontogenesisThe data on the dynamics of changes in morphometric body indices, survival and fertility from the 3rd to the 5th generation in the sturgeon hybrid are presented. The data of experimental studies conducted in the period 2002–2018 under controlled conditions of closed systems of VNIRO in the Moscow region (Russia), for spawners and offspring of the Burtsevskaya bester breed (Huso huso (Linnaeus) × Acipenser ruthenus (Linnaeus)) are summarized. Methods of intravital eggs extraction, ultrasound diagnostics, biopsy with the probe and anesthesia are applied. It has been established that the 5th generation of the «Burtsevskaya» breed of Bester retains the main differences from the parental forms. Embryonic disorders and their level in the offspring of the 5th generation of the Burtsev Bester are similar to the previous generations, with the exception of the “severe variants” noted for F2. There was a decrease in working fecundity in F5  females, and the values of relative fecundity and oosomatic index, on the contrary, increased, which is associated with directional selection for these indicators. In F5  males, the average weight of mature fish increased relative to F3. 

The hydrogeological conditions of the river sections are presented the Dnieper river is located in the areas of wintering pits within the territorial borders of the Vitebsk, Mogilev and Gomel regions of the Republic of Belarus. The hydrochemical regime of wintering pits is considered with an assessment of gas and temperature regimes. In general, the water of the studied wintering pits in the under-ice and ice-free periods in terms of salt composition corresponds to the eutrophic type of water bodies, with a satisfactory gas regime, and is suitable for fisheries. The ichthyofauna of the river was analyzed. Dnepr of the upper, middle and lower sections of the river, the percentage of fish families prone to occurrence in winter was noted — cyprinids — 70.4 %, perch — 21.3 %, pike — 4.7 %, sturgeon and cod — 3.6 %. Invertebrates, gastropod molluscs, were identified, which may be bioindicators of the hydroecological state of the watercourse. An assumption was made about the hydroecological state of the river Dnepr on the studied aspects.

The Arctic belt of the Lena River basin includes part of its lower reaches, delta and more than 30,000 lakes. The reservoirs play an important role in forming the fauna of the non-migratory, semi-anadromous and anadromous fish. The zooplankton in the river is mainly represented by the cladocerans and the immature stages of copepods, and rotifers. The number and biomass made 185–270 individuals/m3  and 0.879–1.766 mg/m3 , with a total biomass of 0.005 g/m3 . The lake zooplankton is represented by rotifers, copepods, and cladocerans. The biomass of rotifers made 2.54 mg/m3 , copepods — 391.48 mg/m3 , and of cladocerans — 823.37, with a total biomass of 1.21 g/m3 . The river zoobenthos is represented by oligochaetes, mollusks, larvae of chironomids, and midges. The number and biomass made 80–120 individuals/m2  and 0.1–0.23 g/m2 , with a total biomass of 0.15 g/m3 . The lake zoobenthos is represented by oligochaetes, mollusks, chironomids, gammarids, branchiopods and phyllopods, water louse, larvae of day-flies, caddis flies, and caddis worms. The biomass of oligochaetes made 4.1 g/m2 , of mollusks — 2.8 g/m2 , and of chironomids — 0.6 g/m2 , with a total biomass of 8.2 g/m2  and a density of 1166 individuals/m2 . The ichthyofauna is 88.5 % freshwater, semi-anadromous and anadromous fish. Marine fish are represented by 4 species. The lakes are inhabited by C. peled, Salvelinus alpinus, S. jacuticus, Pungitius pungitius. H. zschokkei parasites, reducing the nutritional value of the fish, were detected in omul, and D. dendriticum cestodes, dangerous to human health, were detected in omul and muksun. Sturgeon, omul, vendace, muksun, nelma, broad whitefish, Siberian whitefish, lenok, round whitefish, tugun, grayling, dace, burbot, ruff, perch, roach, ide, and pike are fished commercially, which is 51.4 % of the total species composition of the ichthyofauna of the Arctic belt of the Lena basin. The long-term annual average (1940–2020) commercial catch of nelma, muksun, broad whitefish and vendace is 1.61 thousand tons, and taking into account IUU fishing — about 4.8 thousand tons.

The spectrophotometric method of measuring chlorophyll makes it possible, without additional costs, using pigment indices to obtain valuable information on the state of primary producers of the water column and bottom sediments of all types of water bodies, regardless of their trophic status and the state of phytoplankton. Any ecosystem is characterized by a certain pigment background, depending on the presence of plant communities that produce primary production. Changes in pigment characteristics occur interrelatedly and retain their direction in the course of seasonal and long-term succession of producer communities. The determination of spectral indices in water and bottom sediments makes it possible to use them as integral indicators in assessing the ecological state of water bodies in Belarus. The indices for assessing the share of cyanoprokaryotes in the total phytoplankton biomass (Е₄₅₀/Е₄₈₀) and the share of pheopigments (Е₄₃₀/Е₄₁₂) in total chlorophyll-a are of the greatest value and practical significance. Calculated and tested pigment indices reflecting the state of primary producers: Е₄₅₀/Е₄₈₀ and Е₄₃₀/Е₄₁₂. A close relationship between the Е₄₅₀/Е₄₈₀ index and the proportion of cyanoprokaryotes in the total phytoplankton biomass (r=-0.81) was revealed, on the basis of which a scale was compiled for an approximate assessment of the proportion of cyanoprokaryotes by the value of the Е₄₅₀/Е₄₈₀ index. A significant relationship was also observed between the Е₄₃₀/Е₄₁₂index and the proportion of pheopigments in total chlorophyll-a (r=-0.78). For each index, the range of fluctuations was calculated depending on the type of water body, and threshold values were determined. Based on the obtained pigment characteristics, a database was compiled for each investigated water body.

The paper presents results of studies daily vertical distribution of two relict copepod species in the lakes of Belarus — Limnocalanus macrurus (Sars, 1863) and Eurytemora lacustris (Poppe, 1887). These species live in the hypolimnion in summer and belong to the cold-loving fauna, but their distribution has specific features. E. lacustris has two density peaks due to its structure of different ages and is located higher relative to the bottom than L. macrurus, which is characterized by a single bottom population growth.

The paper presents results of studies species composition, abundance and vertical distribution of pelagic zooplankton in the Dolgoye Lake. Maximum animal densities pointed out in the surface well-heated and aerated layers of epilimnion. Metalimnion and hypolimnion zones characterized by lower values of total abundance. There are different in maximum of crustaceans and rotifers abundance. Most populations have species-specific features of vertical distribution and prefer the certain layers of water.

At the first time, zoobenthocenoses of the eutrophic Kruglik lake were established. Four cenoses were identified, located at different depths. The greatest coenotic diversity observed in the littoral and sublittoral zones. The low diversity of the profundal zone was due to the absence of dissolved oxygen.

The Chinese sleeper, Perccottus glenii Dybowski, 1877, is one of the most common alien fish species in Eurasia. On the territory of Belarus, it was first discovered in the 1970s in small ponds located within the city of Minsk. In the city, located on the watershed of the Black and Baltic Seas, there were the largest number of water bodies inhabited by this species: until the middle of the 2000s. it inhabited almost all separate reservoirs and some sections of the city’s watercourses, its numbers in them were relatively stable. Studies conducted in 2020–2022 showed both a decrease in the number of water bodies in which the species is present and a general decrease in its abundance compared to the period 1996–2005. For the period 1996–2005 in the city and its environs, 82 water bodies were identified, in which the Chinese sleeper lived, for the period 2020–2022 — in 43, in 17 of which its number remained stable, and in 26 it decreased. The Chinese sleeper is included in the urban ichthyofauna complex and inhabits water bodies, starting from the smallest ones. The most favorable living conditions for it are formed in small stagnant, moderately overgrown with aquatic vegetation and moderately cluttered, with relatively clean water, water bodies. In most of them, it constantly lives together with other fish species, without reducing their numbers, which is due to both external factors and lifestyle of this species.

There have been 13 helminth species in goldfish in Belarus — Khawia sinensis Hsu, 1935, Neogryporhynchus cheilancristrotus (Wedl, 1855), Dactylogyrus anchoratus (Dujardin, 1845), Dactylogyrus dulkeiti Bychowsky, 1936, Dactylogyrus intermedius (Wegener, 1909), Dactylogyrus vastator Nybelin, 1924, Gyrodactylus medius Kathariner, 1893, Diplozoon paradoxum Nordmann, 1832, Paracoenogonimus ovatus Katsurada, 1914, Posthodiplostomum cuticola (Nordmann, 1832), Diplostomum spathaceum Rudolphi, 1819, Tylodelphys clavata Nordmann, 1832, Ichthyocotylurus pileatus (Rudolphi, 1802). The helminth fauna of this fish species in water bodies of Belarus is primarily composed by monogeneas (6 species) and tremadodes (5 species), which is 42.8 % and 35.7 % of the species composition of parasitic worms. This list includes only 2 species of Cestodes. It should be emphasized that these types of helminths are widespread, and registered with a wide range of native fish species. The analysis of the literature and our own data demonstrated that in Belarus in the fauna of parasitic worms of goldfish 9 species are characteristic of https://context.reverso.net/%D0%BF%D0%B5%D1%80%D0%B5%D0%B2%D0%BE%D0%B4/%D0%B0%D0%BD%D0%B3%D0%BB%D0%B8%D0%B9%D1%81%D0%BA%D0%B8%D0%B9-%D1%80%D1%83%D1%81%D1%81%D0%BA%D0%B8%D0%B9/characteristic+of native fish species. The parasite fauna fo rmation of this fish species in water bodies of Belarus is in the direction of its participation in maintaining the number of parasites of native fish species and expanding the circle of hosts of native species of parasitic worms.

The effect of 5 and 15 % water extracts of the brown algae Laminariacolax aecidioides on the biochemical blood parameters of juveniles Clarias gariepinus was studied. It was shown the content of fucoidan fractions (about 12 %) was comparable with its concentration in macroalgae thalli. Therefore, the possibility of using L. aecidioides as an alternative source of these polysaccharides was proposed. An assessment of the effect of the extract on the biochemical parameters of the blood of catfish revealed a positive effect of 5 % of the extract on the state of the liver, kidney and carbohydrate metabolism of fish, while higher concentrations of the extract (15 %) disrupted the functioning of these organs, which was accompanied by a deviation from the norm of AST, alkaline phosphatase and creatinine.

This article presents the results of all-season studies of the bacterioflora of different fish species bred in fish farms in Belarus and Uzbekistan. The species composition of bacillus and cocci fish microflora in both countries was determined. Potentially dangerous for fish representatives of bacterioflora are noted. The data of bacterial contamination of the aquatic environment in which the fish lives is also determined, quantitatively expressed as an indicator of the total microbial number. Possible reasons for increasing this indicator above the maximum permissible values are considered. It was established that the bacterioflora of fish in Belarus during the research period was represented by 22 species of bacteria, including 11 species of bacillus and 11 species of cocci; fish bacterioflora of Uzbekistan — 7 species, including 6 species of bacillus flora and 1 species of cocci microflora. Common representatives of the bacterioflora of fish in both countries are bacteria of the Kocuria (Kocuria kristinae and Kocuria rosea) and Aeromonas hydrophila.

The basic principles of increasing the resilience of poikilothermic animals — objects of aquaculture are scientifically substantiated and formulated. The effectiveness of the implementation of the principle of reducing the antigenic load and the principles of increasing the natural and specific resistance of fish in aquaculture conditions is shown. The integration of these principles into the fishery industry will allow creating stable communities in mono- and polyculture of fish and increasing fish productivity