The results on fisheries activities and its production base for 2021 are presented. The main areas of fisheries management in the Republic of Belarus are aquaculture (fish farming) and fisheries management (fishing). More than 600 legal entities and individuals are engaged in fishery activities in the country, including 15 specialized pond fish farms of republican and municipal forms of ownership. The total number of industrial farms is 15. At the beginning of 2022, no more than 19.9 thousand hectares of outgrowth and feeding ponds, up to 8.6 thousand hectares of adapted ponds and watered quarries and 3.6 thousand m2 of cages and pools of industrial complexes are suitable for growing fish products of their own production. The main direction remains pond fishing, which accounts for more than 98 % of the total production of commercial fish. Up to 15 species of fish are grown in commercial aquaculture in Belarus.
The share of carp in the total production volume is gradually decreasing. In 2021, the share of carp was reduced from 92–98 % to 71.1 %, the share of herbivores slightly increased among additional fish (up to 13.8 %), and a decrease in the share of crucian carp was noted. The basis of the production of “valuable” species in general was rainbow trout and sturgeon fish (77 % and 22 %, respectively), the African catfish accounts for the least — less than 1 %. Given the current availability of food and the maximum use of polyculture resources, the potential catch of marketable pond fish is estimated at 9.11 thousand tons, the potential production of “valuable” fish species in the industrial fish farming of Belarus is up to 500–600 tons, the potential catch on leased areas may amount to about 800 tons per year, the estimated volume of stable catch of crayfish from the reservoirs of Belarus can reach about 5 tons per year.

The article presents the results of a 10-year study of fishery indicators of two lines of breeding Belarusian mirror carp of the fourth and fifth generations. Each of the lines includes five generations.
High variability of body weight and survival of youngsters was noted between the fourth-generation generations. The average weight of fingerlings of the first line averaged 29.0 g with fluctuations from 17.7 to 39.2 g, in the second line the average weight of fingerlings is higher and is 44.7 g (38.0–48.3 g). The average survival rate of youngsters of the first line averaged 39.8 %, with fluctuations from 27.3 to 55.8 %, in the second 34.2 % with fluctuations of 33.9–34.4 %.
In the fifth generation, the weight of the fingerlings varied significantly less than in the fourth. Fluctuations in the first line ranged from 32.8 to 33.8 g, in the second from 26.3 to 31.6 g. The survival rate of fifth-generation fingerlings mainly varied from 28.0 to 44.0 %, with the exception of the third generation of the second line, in which this indicator is significantly higher (65.0 %). In general, the comparison of youngsters of two generations indicates an increase in average body weight and a decrease in the variability of this indicator in the fifth generation compared to the fourth. On average, in the fourth and fifth breeding generations of the Belarusian mirror carp, the level of average weight and survival of fingerlings meets regulatory requirements.

The article presents the results of a study of phenotypic signs of disequilibrium groups of the tench population of the SPU “Isobelino”. Some morphometric indicators of the tench repair herd were compared with archival data.

It was revealed that after wintering, the exterior indicators of the producers of the black Amur were satisfactory and met the standards for the formation of repair and breeding herds. The absolute total length of the selected individuals of the repair — brood herd of the black Amur varied from 98 cm to 118 cm, averaging 104.3±1.93 cm, the length to the end of the scaly cover varied within 83-101 cm, with an average value of 90.9±1.81 cm. The weight of the same fish varied from 8.6 kg to 16.7 kg, which averaged 11.77±0.78 kg. The black cupid has the highest coefficient of variation in body weight (20.97 %). All absolute morphometric indicators characterizing the length, width and height of various body parts were increased in the group with a higher average weight. The variability of these characteristics in the black Amur of the population from the «Selets» fish farm is insignificant (coefficient of variation 3.85–8.70 %). Fulton fatness coefficients characterizing the physiological state of fish after wintering in most of the examined individuals of the black amur (80 %) were at an acceptable level for this species and age of fish, varying within 1.47–1.75 %. The index of progonicity in the examined black amur was characteristic of progonistic fish species such as the black amur (4.04–4.59 units. with an average value of 4.30 units) In general, the level of variability in the progonicity index turned out to be low and amounted to 3.85 %, and the variability of the variation series on this basis can be considered insignificant. The heterosexual representatives of the repair-brood herd of the black Amur were characterized by pronounced sexual dimorphism. The same-aged females were noticeably superior to males in body weight (13.7±0.81 kg and 9.83±0.48 kg, respectively) and some external indicators, such as the fatness coefficient (1.58±0.08 % and 1.52±0.03 %), girth index (60.59±1.20 % and 55.48±0.92 %), high-back index (23.51±0.55 and 22.70±0.44 %).

The article presents the results of wintering of the Amur carp yearling of the ninth generation, including three generations. The average weight of youngsters of carp crossbreeds obtained by fertilizing the eggs of females from the Belarusian population (F9, I generation) imported from the collection of the VNIIPRH milk was 35.2 g (experimental crossbreed I) and 32.5 g (II), which turned out to be lower than that of youngsters from the Belarusian population (54.0 g). The average weight of carp yearlings (F9, II generation) was 34.6 g, which is lower than that of purebred groups of Belarusian and foreign breeding (41.6 and 38.5 g, respectively). The third generation of the ninth generation of the Amur carp is represented by yearlings from the Belarusian population and mixed experimental groups (4 crossbreeds) obtained using imported milk. The offspring of a carp from the Belarusian population was considered as a control. The average weight of yearlings of the experimental groups of carp ranged from 10.4 g (P1) to 31.3 g (P4), averaging 24.1 g. The average level of body weight loss in carp yearlings (F9, I and II generations) turned out to be lower, and the survival rate, on the contrary, is higher than in carp of the collection purebred carp groups of Belarusian and foreign breeding wintering together. The level of winter hardiness of the Amur carp was significantly higher than that of the Belarusian lines wintering in the same conditions.

The article presents the results of comparing the biochemical composition of fingerlings and yearlings of crosses obtained from breeding mirror carp and experimental groups of Amur carp. Experimental crosses characterized by elevated levels of dry matter, fat, and protein have been established.
On average, the youngsters of hybrids showed a tendency to increase the content of dry matter, fat and minerals in comparison with the parent forms, as well as the average level of these indicators in collectible Belarusian and foreign breeds.
During wintering, there was a decrease in the content of dry matter, fat and protein in the body of fish and an increase in the content of minerals (ash). A decrease in the consumption of nutrients and, above all, the content of dry matter, fat and protein, are characteristic of more winter-hardy breeds. The expense of dry matter and fat during the winter period in carp hybrids turned out to be slightly higher than in sazan and approached the breeding carp (mother breed). In terms of the nutrient loss in winter, hybrids of breeding carp with sazan and their parent forms were an intermediate position between the collection groups of Belarusian and foreign breeding.
Experimental crosses characterized by elevated levels of dry matter, fat, and protein have been established.

The article presents data on the reproductive qualities of the Amur sazan in purebred breeding and when it is used to obtain crossbreeds with collection carp of Belarusian and foreign selection. When forming the first and third reproductions of the ninth generation of the collection Amur carp, imported genetic material (milk) was used. Sazan females were previously genetically labeled for transferrin.
In accordance with the work program, 12 crossings (11 experimental and 1 control) of Amur sazan and carp of different breeds were carried out in order to study the combination ability of hybrids.
Evaluated:
• reproductive qualities of carp females used for caviar production,
• survivability of eggs in various crosses,
• linear dimensions and live weight of larvae of purebred carp and crosses.
The working fecundity of females of the Amur carp averaged 174.72 thousand eggs, with a high level of trait variability: from 121.36 to 225.49 thousand eggs. 
The average fertility of pure breeding Amur sazan eggs was 71 %. When hybrids were obtained from sazan females and males of various carp breeds, the proportion of live eggs after one day of development was 82.0 %. When obtaining hybrids from collection females of carp of Belarusian breeds, the proportion of live eggs was 81.7 %, with fluctuations from 67 % (Lakhvinian carp x sazan) to 96 % (three prim carp x sazan). The average value of the fertilization of eggs when obtaining hybrids from collection females of foreign selection carp breeds, with slight fluctuations, was 47.0 %.
The mass of three-day-old sazan larvae averaged 4.0±0.06 mg, purebred carp of different breeds 3.1±0.21 mg, crosses of sazan (♀) with carp (♂) 2.9±0.02 mg, carp (♀) with sazan (♂) 3.2±0.02 mg. The length of three-dayold larvae of sazan was 5.5±0.07 mm, carp 6.7±0.05 mm, crosses of sazan (♀) with carp (♂) 6.1±0.03 mm, carp (♀) with sazan (♂) 6.3±0.06 mm. The largest larva weighing 4.5 ± 0.08 mg was obtained from crossing females of the Isobelinsky breed (layering three prim) with sazan males.
The data obtained are necessary to calculate the required number of spawners to obtain one or another cross and to select a cross with a higher survival rate for stocking commercial reservoirs.

The goldfish (Carassius auratus s. lato) populations from the sections of the Dnieper (in Bykhov and Bragin districts, Belarus) and Pripyat (in Mozyr district, Belarus) rivers sections were investigated. Overall 436 goldfish specimens were collected. The populations sexual structure and meristic traits diversity inside and between populations were studied. It has been shown that the Dnieper and Pripyat rivers sections studied are inhabited with bisexual goldfish populations, that corresponds to the amphimyctic type of reproduction. The sexual structure distinctions between populations has been revealed. The goldfish population from the Dnieper river (Bykhov district) is characterized by the males’ qualitative dominance (1♀:1,18♂), while the females prevailed in the populations from the Pripyat and Dnieper (Bragin district) rivers (1,23♀:1♂ and 1,30♀:1♂ respectively). The meristic descriptions of populations were composed and it has been shown that they are common for populations of goldfish from Belarusian water objects. Statistically significant differences between populations in 5 of the 12 meristic traits studied were revealed. Two populations from Dnieper are significally distinct only in 1 trait, and the population from Pripyat differs from them in 3 (Dnieper, Bykhov district) and 4 (Dnieper, Bragin district) meristic traits. The phene pools are most similar in the populations from Dnieper, too, and the phene pool of the Pripyat population shows some differences from them. 

The results of using the new enzyme additive in the composition of mixed feeds for growing one-year carp in fish ponds are considered in the article. The hydrochemical regime of the fish ponds, development of the natural feed base (zooplankton, zoobenthos) were studied during the season. It was found that the hydrochemical parameters did not exceed the limits of technological norms. Ponds were characterized by the natural feed base’ low productivity. The bulk of fish products in the ponds was made using artificial mixed feeds. The results of fish cultivation showed that that the use of the new enzyme additive Fekord-Aqua in the composition ofgranular mixed feeds increases the average one-year piece weight by 23.0 %, fish productivity by 4.4 % and reduces feed costs by 23.4 % for fish growth. The use of Fekord Aqua in extruded mixed feeds increases the average one-year piece weight by 6.8%, survival rate by 6.9%, fish productivity by 14.9 % and reduces feed costs by 25,5 %. The muscles of one-year piecesexperimental groupsaccumulated more dry matter by 2.3–9.9 %, the content of raw protein was increased by 2.5–6.9 %, raw fat by 1.9–22.2 % than in the muscles of one-year piecescontrol group. Thus, a new enzyme substance using makes it possible to improve protein, lipid, mineral metabolism, digestibility of feed as well as growing a one-year piece, physiologically ready for wintering.

: The article presents an analysis of materials obtained in the course of studies of hydrobiocenoses of small ponds of breeding and genetic center “Isobelino” (Molodechno district of Minsk region, 2nd zone of fish farming), stocked in a different ratio, depending on the experimental scheme used, by cyprinid fish, in particular, larvae of grass carp in monoculture at a density of 25 to 100 thousand individuals per hectare, larvae of the chinese roach at a density of 20 thousand individuals per hectare, yearlings of the ide in monoculture at a density of 6500 individuals per hectare and in polyculture with carp, grass carp, mottled carp and european catfish. In accordance with the nature of the formed ichthyocenoses, different feeding schemes were used. n the course of the research, it was found that the quantitative and taxonomic characteristics of phyto- and zooplankton communities largely depend on the structure and quantitative characteristics of the ichthyofauna formed in ponds. Higher quantitative indicators of zooplankton community development are observed in conditions of distribution of matter and energy flows along the detritus chain, in ponds inhabited by fish polyculture, more intensively involving organic matter of ponds in the food chain, higher rates of mineralization of organic matter and, accordingly, the return of carbon and biogens to the circulation of substances in the system are natural here. Low planting densities of the Amur white naturally exert significantly less pressure on zooplankton communities compared to variants with higher planting densities, therefore, higher biomass and zooplankton production is achieved, as well as potential fish production due to plankton communities. The products of planktonic communities are most effectively converted into fish products in ponds where the ichthyofauna is represented by a polyculture of pond carp fish. The potential fish productivity here reached 306,56 kg per hectare, while 300,0 kg per hectare of fish products could be obtained due to zooplankton.

The work analyzes the IUU fishing of nelma Stenodus leucichthys nelma (Pallas, 1773), muksun Coregonus muksun (Pallas, 1814), Arctic cisco C. autumnalis (Pallas, 1776) and Siberian cisco C. sardinella Valenciennes, 1848, whose commercial fishing in the Lena River makes 60 % of all commercial fishery species’ catch. IUU fishing of nelma, muksun, Arctic cisco, Siberian cisco in the Lena basin exceeds their commercial fishing (1528,8 t) twofold and makes 3104,9 t. Damage caused to Coregonidae species in the Lena River basin by the IUU fishing is estimated at RUB 2028,3 million. Control of Coregonidae species’ fishing only by setting quotas is ineffective as the decrease of quotas automatically triggers the increase of IUU fishing, including household poaching. To increase the efficiency of control over the water biological resources, it is proposed to establish a network of fish-receiving stations, controlled by the Russian Federal Agency for Fishery, which will allow to monitor the volume of the young fish bycatch and control fishing. Inaccurate information distorts the official fishery statistics, which impairs the accuracy of commercial stock prediction and requires adjustment of allowable catch with account of IUU fishing. To counter IUU fishing, it is necessary to establish a mechanism for tracking the sequence of fish products shipping to the market.

Industrial fish farming is becoming increasingly developed, and, in particular, the cultivation of aquatic organisms in recirculating aquaculture system (RAS). These systems are promising due to the possibility of growing fish at high planting densities with minimal use of water resources. To bring the circulating waters to the values of indicators necessary for the cultivation of a certain type of fish, equipment is used (mechanical and biological filtration systems, disinfection, aeration, etc.), which allows to maintain the factors of the growing environment at the required technological level. The resource efficiency and performance of the entire system depends on the efficiency of this equipment. One of the most important elements of RAS is a biofilter: the processes of biological oxidation and redox reactions carried out by microorganisms in it make it possible to reduce the concentration of nitrogenous compounds in the system. The main factors influencing the efficiency of the biological filtration system are determined: temperature from 13 to 28 °C, concentration of dissolved oxygen at least 2 mg/l at the outlet of the biofilter, concentration of total ammonium nitrogen up to 4.5 mg/l, pH 8.0–8.2 and the absence of direct sunlight on the open part of the biofilter. RAS makes it possible to control these factors affecting the flow of technological processes. However, the adjustment of the hydrogen index causes difficulties for the service personnel. It is not always possible to make the correct calculation of the required amount of alkali or acid, given the high buffering of circulating waters and to maintain pH values at the same level. In the process of such an adjustment, side chemical compounds are formed, which subsequently need to be removed from the system, increasing the total water consumption of the RAS. There are methods of electrolysis reagentless pH correction. A non-reactive pH corrector with an anode and cathode made of inert bulk materials (graphite) has been developed. Testing of such a system made it possible to correct the values of the hydrogen index of the treated water to pH 6.24±0.114 and 8.10±0.158 at the initial values of 7.4. The processing voltage was 18.3 Volts, Current 2.1 Amperes, with water mineralization (TDS) = 287 ppm. The obtained values make it possible to separate the flows in the system to create favorable conditions for the passage of biotechnological processes in the biofilter, and to influence the ammonia-ammonium balance in fish tanks.

Working of composts, including local bioresources, to stimulate the development of the natural food base of ponds and increase their productivity, is an urgent task in the light of the intensification of fish breeding processes. Thereby, on the basе of the Laboratory of hydrobiology and hydrochemistry of the RUE «Fish Industry Institute», 10 variants of multicomponent compostable mixtures, based on local raw materials from fish farms, were laid down in 2021, using various methods of their bioactivation. Chemical parameters of initial raw materials, as well as the quality of mature compost mixtures were studied, the dynamics of the main physical and chemical parameters in the process of their maturation (temperature, pH, humidity, weight loss, content of organic substances, nitrogen, phosphorus and potassium) were analyzed. 2 compositions of biocomposts with the best quality indicators and minimum maturation time were identified.

Preliminary results of identifying the causes of mass mortality of silver carp in the water bodies of Belarus in the period 2018–2022 are presented. Abiotic and biotic factors that could cause the death of crucian carp are considered, including the hydrochemical regime, water bloom with a predominance of cyanobacteria, the levels of total bacterial contamination of water by saprophytic microflora, the presence of infectious and parasitic diseases. The structure of carp catches, their size-age and sex composition, the state of the gonads at the time of capture were analyzed. The state and degree of maturity of the gonads allows us to assert that crucian spawning is observed until August inclusive, which certainly affects the level of fish resistance. The presence of bisexual populations in all analyzed reservoirs was established, with a sex ratio close to 1:2. The growing relative abundance in carp populations confirms the efficiency of its reproduction even in the absence of natural sperm donors. An assumption was made about the complex impact of negative environmental factors against the background of a seasonal decrease in fish resistance due to a change in the breeding strategy.

Information is presented on clarifying the location of wintering pits in the Dnieper and Sozh rivers within their flow on the territory of Belarus, in order to organize the protection of their fish stocks, with the development of an interactive map and a mobile application with the possibility of visualization and navigation. 74 wintering pits were identified, of which: 42 — on the river. Dnepr, 32 — on the river. Sozh with indication of geographical coordinates and description of binding to the area. The main bathymetric and hydrometric characteristics of wintering pits were studied, and a hydrochemical analysis was carried out in the area of their location. On average, the depth of the sections of the rivers to the Dnieper and Sozh at the locations of wintering pits is about 5–6 m, the minimum recorded depth is 3 m, the maximum is 20 m. The smallest area of the pit was 0.5 ha, the largest — 42 ha. The flow velocity was from 0.01 to 0.9 m/s. Studies of the temperature and oxygen regimes of water in the areas where wintering pits are located on the river. The Dnieper and Sozh did not reveal deviations from similar indicators for other sections of the channel.

The new version of the Rules for recreational fishing (Decree of the President of the Republic of Belarus “On Fishing and Fisheries” dated July 21, 2021 No. 284) introduced a ban on all fishing within the boundaries of wintering pits, which required updating the lists and boundaries of pits for different categories of fishing grounds. The Fish Industry Institute of the National Academy of Sciences of Belarus together with the Laboratory of Ichthyology of the SNPO “Scientific and Practical Center of the National Academy of Sciences of Belarus for Bioresources” conduct research on watercourses and reservoirs of the Republic of Belarus to clarify the boundaries of wintering pits. Currently, the list of wintering pits has been updated in relation to the channel sections of the rivers of the Neman basin with clarification of their boundaries. Hydrochemical studies were carried out at the sites of wintering pits on the river. Neman and Viliya within the territorial boundaries of the Grodno region. Collected hydrochemical, hydrological and bathymetric data on part of the wintering pits. On the river Neman total identified 27 wintering pits on the river Viliya — 5. The pits are located on meanders with indicators of high curvature of the channel turn, in creeks and flooded quarries. On average, the depths at the locations of the wintering pits rr. Neman and Viliya are about 4–5 m, the minimum marked depth is 3 m, the maximum is 11 m.

In the second half of the 1980 s the actively spreading invasive mollusk Dreissena polymorpha invaded Lake Batorino. The first decades after that the population has been actively spreading, increasing its abundance and biomass. However, after 2002, the population has sharply declined and dreissena became practically absent in benthic samples. Since the lake was a eutrophic one and due to its large catchment area and big number of reclamation channels flowing into the lake, it tends to silt, and the conditions in the lake became not suitable for intensive development of zebra mussel. In addition, the macrophytes, which usually serve as the main substrate for Dreissena in Naroch Lakes, consist of species whose morphological structure is not suitable for the massive attachment of Dreissena individuals to them. Thus, after an active period of population development immediately after the introduction and subsequent recession, the population in the lake is currently extremely small, which is mainly due to the lack of suitable substrate for fixing zebra mussels. Due to the difficulties for the zebra mussel population development under these conditions, nowadays it did not cause significant damage to the native species of large bivalves whose recovery became possible in recent years.

The data of pikeperch commercial landings from the Dryvyaty and Boginskoe lakes in the last decades were analyzed. The growth, size and age of fish from the landings were studied. The usable stock of pikeperch in the lakes was determined. The biological analysis of studied fish was carried out using standard ichthyological techniques. It has been shown that last years the pikeperch become increasingly important in the commercial landings from the Dryvyaty and Boginskoe lakes. In 1990s-early 2000s its landings in Dryvyaty didn’t exceed 1-6 centners per year, and only a sporadic catch was in the Boginskoe lake. Last 10 years the annual pikeperch landings were between 11 and 73 centners in Dryvyaty, and up to 14 centners in Boginskoe lake. Its share in the landings increased even more sharply. The base of landings in Dryvyaty was composed of 5-years old specimens, with the 6-years old ones share also was high. The prevalent body length was 45–49 cm, and the observed landings structure seems to be reasonable because most of the specimens caught had already took part in spawning 1–2 times. Instead of it, the base of landings in Boginskoe was represented by 4- and 5-years old fish with prevalent length of 40–49 cm. That seems to be less reasonable because the part of 4-years specimens are being caught before their reproduction. Nowadays the pikeperch growth in both lakes is characterized as fast, but while the linear growth is nearly same in both lakes, the pikeperch from the Dryvyaty lake shows more rapid weight growth. The data obtained show the sufficient food supply for the pikeperch in bolt lakes and the possibility of its further number increase. The current estimated pikeperch usable stock in the Dryvyaty lake is 19,51 kg/ha, and in Boginskoe lake is 18,92 kg/ha that is significantly more that was in 1980s-1990s.

The paper presents the results of a parasitological survey of fish from water ecosystems of the Minsk City and the Minsk region, obtained during the season of 2021. 14 fish species from 10 open water bodies were examined. 10 species of ecto- and endoparasites of fish belonging to different classes were registered: 1 species of ciliates (Trichodina sp.), 1 species of crustaceans (Argulus sp.), 2 species of monogenetic flukes (Gyrodactylus sp. and Dactylogyrus sp.), 1 species of nematodes (Camallanus lacustris), 1 species of cestodes (Ligula intestinalis) and 4 species of trematodes (Diplostomum sp., Aspidogaster sp., Posthodiplostomum cuticola, Tylodelphys conifera).
Pathogens of diseases that pose a danger to mammals, incl. person humman, have not been identified.

The article presents the results of the analysis of the sensitivity of the microflora of sturgeon fish species to such antibiotics as enrofloxacin, neomycin, ciprofloxacin, levofloxacin and rifampicin. Data were obtained on the antibiotic sensitivity of 81 strains isolated from various biological material of fish with clinical manifestations of the infectious process and without pathologies. All the results obtained for the zones of growth inhibition of the bacterial culture (mm) are ranked according to the degree of sensitivity. It has been established that rod-shaped bacteria are slightly more sensitive to the action of fluoroquinolones and neomycin, compared with cocci. However, 69.1 % of the studied rod-shaped bacteria were found to be resistant to rifampicin (including 75.5 % of all studied gramnegative rods that are conditionally pathogenic for fish), while only 19.2 % of cocci showed resistance to this drug.