When carrying out activities aimed at maintaining the number of sturgeon through the release of juveniles into the natural habitat, a competent genetic approach is necessary. This, first of all, will allow an assessment of the genetic diversity of the breeding stock and the degree of kinship of fish producers, to exclude the genetic degeneration of the population due to inbreeding. The aim of the work was to carry out genetic monitoring of Russian sturgeon and beluga from brood stocks of the scientific and experimental complex of aquaculture “BIOS” of the Volga-Caspian branch of VNIRO in the period 2020–2022. Genotyping of the producers was carried out according to five nuclear markers and a fragment of the control region of mitochondrial DNA. Crossing shemes of sturgeons from broodstocks were formed taking into account the coefficients of genetic relationship. According to the results of molecular genetic studies, 12–22 mitochondrial haplotypes in Russian sturgeon females, and 3–5 mitochondrial haplotypes in beluga females were identified. Species-specific dominant alleles were identified in microsatellite loci of sturgeons Russian sturgeon spawners were characterized by a high level of genetic diversity for nuclear and mitochondrial markers. The most difficult situation is with the genetic diversity of beluga due to the small number of mature spawners in the broodstock. Genetic monitoring of the artificial reproduction of Russian sturgeon and beluga is necessary to obtain genetically diverse offspring in the terms of a reduction in sturgeon fishes in the Volga-Caspian fishery basin.

The aim of the work was to carry out genetic monitoring of the natural reproduction of juveniles (larvae and underyearlings) of sterlet (Acipenser ruthenus Linnaeus, 1958), caught in the middle and lower spawning zones of the Volga River for the period 2021–2022, which is necessary and relevant in the context of a decrease in the number of sturgeon species of fish. The study of fish was carried out according to five nuclear markers and a fragment of the control region of mitochondrial DNA.According to the results of microsatellite analysis, sterlet individuals were characterized by species-specific dominant alleles and high values of the main indicators of genetic diversity: the number of alleles, allelic diversity and heterozygosity, and a slight deficit of heterozygotes was noted. By analyzing of the nucleotide sequences of the mtDNA D-loop region a high level of diversity of maternally inherited haplotypes was revealed, reflecting the number of females involved in natural reproduction. According to the monitoring data, no differences in the distribution and number of identified variants of the D-loop region were registered in the interannual aspect. During the study period, 48 sterlet mitochondrial haplotypes were recorded, of which 18 mtDNA variations were unique, occurring in the Volga-Caspian fishery basin. In the study of sterlet larvae by molecular genetic methods in the Volga River was revealed the process of hybridization between stellate sturgeon and sterlet (Acipenser stellatus × Acipenser ruthenus).

The results of a study and analysis of the physiological and biochemical parameters of the blood of beluga females (Huso huso) during the spawning period were presented in the article. The data were obtained in the laboratory of molecular genetics and physiology of the Volga-Caspian branch of the VNIRO (CaspNIRKH) in the period 2020–2022 during the monitoring of artificial reproduction. We studied females of the V stage of gonads maturity of natural (domesticated stocks) and artificial parameters of blood in beluga females during the spawning period was calculated using descriptive statistics based on parametric and nonparametric criteria. A comparative analysis of females of domesticated stocks and broodstocks revealed an unreliable (p > 0.05) trend of excess of the studied physiological and biochemical parameters in the blood of individuals of artificial generation, with the exception of beta-lipoproteins. The established ranges of blood components characterized the heterogeneity of the functional state of spawners at the spawning stage. There was a positive correlation (p < 0.05) between cholesterol and total lipids (r = +0.56), cholesterol and beta-lipoproteins (r = +0.74), beta-lipoproteins and total lipids (r = +0.44),hemoglobin and total serum protein (r = +0.58). The recorded dynamics testified to a unidirectional regularity in the consumption of fish biochemical components for the formation of reproductive products. The results obtained are necessary to assess the “quality” of beluga spawners in order to optimize the technologies for obtaining physiologically high-grade juveniles under conditions of artificial reproduction.

The fishing and biological characteristics of the common sprat (Clupeonella cultriventris caspia Svetovidov, 1941), caught along the coast of the Caspian Sea in the area of Makhachkala, the Republic of Dagestan, were obtained. Examination of the fish showed that the individuals were in a spawning state. In the muscles, the content of the main reserve and energy substances of the body — total lipids and water-soluble protein — was studied. A significant (p < 0.05) positive correlation was registered in females and males between fish weight and fishing length: (r = +0.87) and (r = +0.85), respectively. The physiological state of the common sprat in terms of the content of total lipids and water-soluble protein in the muscle tissue is satisfactory. The tendency of the highest content of total lipids in the muscles of females compared to males was registered, since individuals need a larger energy reserve to ensure oogenesis than for spermatogenesis. This is due to the use of muscle lipids to build the gonads and supply with the necessary nutrients for the embryo, and later the larva. In a comparative aspect, there were no significant differences in the content of water-soluble protein in the muscles of males and females during the spawning period. Analysis of the coastal fishery for common sprat with fixed seines in the period 2011–2021 showed that its catch on the Dagestan coast of the Caspian Sea increased from 302.7 tons in 2012 to 1815.0 tons in 2021, which was in direct proportion to the number of fixed seines. In this regard, the most actual task is the development of fishing reserves of this species, which will contribute to the development of the fish extraction and fish processing industry of the Republic of Dagestan.

Comparative results of experimental work on the study of stellate sturgeon offspring obtained using cryopreserved (experimental) and native (control) sperm, carried out at the scientific and experimental complex of aquaculture “BIOS” of the Volga-Caspian branch of VNIRO (CaspNIRKH) in this article were presented. Molecular genetic studies of cryopreserved sperm, females and males from the brood stock of the complex were carried out. In order to select the optimal parental pairs, calculations of genetic relationship of fish spawners were made. The scheme of the experiment was developed. The technological process of working with stellate sturgeon spawners was described: obtaining mature reproductive cells, insemination, incubation of caviar. Holding and breeding of the studied groups of stellate sturgeon juveniles up to standard weight was carried out. Each stage of the research work was subjected to comparative analysis. The genetic diversity of juveniles was studied. As a result of the work carried out, it was found that the group of fish obtained using of cryopreserved sperm had higher weight indicators, compared with the juveniles of the control group obtained from males from the brood stock of “BIOS”, by an average of 16%. In addition, the experimental group had a higher homogeneity compared to the control group, as evidenced by the values of the coefficients of variation. The survival rate of juveniles of the experimental group of fish was higher than the control group by an average of 10%. The stellate sturgeon obtained using cryopreserved sperm was characterized by higher values of the total number of alleles and the absence of a deficit of heterozygotes compared to the control group of juveniles, which is especially important for preserving the diversity of this valuable sturgeon species. The results of the research work carried out will help develop proposals for the formation of artificially created sturgeon brood stocks by replenishing them with juveniles obtained using cryopreserved sperm and having higher fish breeding biological and genetic indicators. This will allow the herd to have a stock of working material from different generations of sturgeon species, which is a promising factor for the conservation of aquatic biological resources and selection in commercial aquaculture.