Russian Sturgeon Research Articles

Sturgeon Biological Parameters in the Ural River (Zhaiyk) of the Republic Kazakhstan

The dynamics of capture of 4 Sturgeon species (family Acipenseridae): Russian sturgeon Acipenser gueldenstaedtii, Sterlet A. ruthenus, Stellate Sturgeon A. stellatus, Beluga Acipenser (Huso huso) in the IUU catches of the Ural (Zhaiyk) River within of the Republic of Kazakhstan borders is done. The annual number of Sturgeons estimated by arrested IUU catches in the period 2012–2018 which demonstrate the fluctuation of the Ural River Sturgeons number as well as male dominance is given. The biological indicators of Ural’s Sturgeons during the period of maximum catches in 2018: sex ratio, age, weight, length, length-weight relationship are given.

Understanding the spleen response of Russian sturgeon (Acipenser gueldenstaedtii) dealing with chronic heat stress and Aeromonas hydrophila challenge

Sturgeon aquaculture has grown in recent years, driven by increasing global demand for its highly valued products. Russian sturgeon (Acipenser gueldenstaedtii), recognised as one of the most valuable species for caviar production, is farmed in several warm-temperate regions. However, the substantial temperature increase due to global warming represents a challenge for developing sturgeon aquaculture. Previously we demonstrated that Russian sturgeon under chronic heat stress (CHS) exhibited a liver metabolic reprogramming to meet energy demands, weakening their innate defences and leading to increased mortality and economic losses. Here, we used RNA-seq technology to analyse regulated genes in the spleen of Russian sturgeons exposed to CHS and challenged with Aeromonas hydrophila. The assembly gave 253,415 unigenes, with 13.7 % having at least one reliable functional annotation. We found that CHS caused mild splenitis and upregulated genes related to protein folding, heat shock response, apoptosis and autophagy while downregulated genes associated with the cell cycle. The cell cycle arrest was maintained upon A. hydrophila challenge in heat-stressed fish, potentially inducing cell senescence. Surprisingly, immunoglobulin heavy and light chains were upregulated in the spleen of stressed sturgeons but not in those maintained at tolerable temperatures; however, no changes in IgM serum levels were observed in any condition. Our findings indicate that long-term exposure to non-tolerable temperatures induced a heat shock response and activated apoptosis and autophagy processes in the spleen. These mechanisms may enable the control of tissue damage and facilitate the recycling of cell components in a condition where the nutrient supply by the liver might be insufficient. Stressed sturgeons challenged with A. hydrophila maintain these mechanisms, which could culminate in cellular senescence.

Extracellular vesicles and citrullination signatures are novel biomarkers in sturgeon (Acipenser gueldenstaedtii) during chronic stress due to seasonal temperature challenge

Acipenser gueldenstaedtii is one of the most cultured sturgeon species worldwide and of considerable economic value for caviar production. There are though considerable challenges around chronic stress responses due to increased summer temperatures, impacting sturgeons’ immune responses and their susceptibility to opportunistic infections. The identification of molecular and cellular pathways involved in stress responses may contribute to identifying novel biomarkers reflective of fish health status, crucial for successful sturgeon aquaculture. Protein citrullination is a calcium-catalysed post-translational modification caused by peptidylarginine deiminases (PADs), altering target protein function and affecting protein interactions in physiological and pathobiological processes. PADs can also modulate extracellular vesicle (EVs) profiles, which play critical roles in cellular communication, via transport of their cargoes (proteins, including post-translationally modified proteins, genetic material and micro-RNAs).This study identified differences in EV signatures, and citrullinated proteins in sera from winter and summer farmed sturegeons. EVs were significantly elevated in sera of the summer chronically stressed group. The citrullinated proteins and associated gene ontology (GO) pathways in sera and serum-EVs of chronically heat stressed A. gueldenstaedtii, showed some changes, with specific citrullinated serum protein targets including alpa-2-macroglobulin, alpha globin, calcium-dependent secretion activator, ceruloplasmin, chemokine XC receptor, complement C3 isoforms, complement C9, plectin, selenoprotein and vitellogenin. In serum-EVs, citrullinated protein cargoes identified only in the chronically stressed summer group included alpha-1-antiproteinase, apolipoprotein B-100, microtubule actin crosslinking factor and histone H3. Biological gene ontology (GO) pathways related to citrullinated serum proteins in the chronically stressed group were associated with innate and adaptive immune responses, stress responses and metabolic processes. In serum-EVs of the heat-stressed group the citrullinome associated with various metabolic GO pathways.In addition to modified citrullinated protein content, Serum-EVs from the stressed summer group showed significantly increased levels of the inflammatory associated miR-155 and the hypoxia-associated miR-210, but significantly reduced levels of the growth-associated miR-206.Our findings highlight roles for protein citrullination and EV signatures in response to chronic heat stress in A. gueldenstaedtii, indicating a trade-off in immunity versus growth and may be of value for sturgeon aquaculture.

Aroma-active compounds in Russian sturgeon (Acipenser gueldenstaedtii) raised in recirculating aquaculture systems

The rearing system affects the nutritional and sensorial qualities of the Russian sturgeon (Acipenser gueldenstaedtii), a niche yet commercially valuable aquaculture species for caviar production. In the present work, we aimed to comprehensively characterize the odorant composition of fillets from Russian sturgeon raised in a recirculating aquaculture system (RAS) and discuss potential sources and formation pathways. A total of 114 odorants were detected through the application of combined sensory-instrumental analyses, of which 88 were successfully identified and 20 substances were found to be among the most potent odor constituents. The most dominant odorants were assigned to several specific substance classes, including aldehydes, alcohols, terpenes, ketones, organic acids, lactones, heterocycles, aromatic hydrocarbons, and sulfur-containing aldehydes. The compounds (E)-hex-2-enal, (Z)-hept-4-enal, cuminaldehyde, non-3-yn-1-ol, 3-carene, 2-methylisoborneol, geosmin, oct-1-en-3-one, nonan-3-one, (Z)-1,5-octadien-3-one, octane-2,3-dione, nonan-2-one, hexanoic acid, γ-crotonolactone, γ-octalactone, 2-acetyl-thiazoline, methional, and (2E,4Z,7Z)-trideca-2,4,7-trienal had high flavor dilution factors and are described for the first time as potent odor-active compounds associated with the Russian sturgeon. Overall, oct-1-en-3-one, (Z)-1,5-octadien-3-one, octane-2,3-dione, nonan-2-one, 2-methylisoborneol, and hexanoic acid had the highest flavor dilution factors. This study offers a basis for future development in the sturgeon RAS industry from the perspective of flavor characterization by providing deep insights into the fundamental composition and origins of the complex world of aquaculture fish aroma.

Next-Generation Sequencing to Determine Changes in the Intestinal Microbiome of Juvenile Sturgeon Hybrid (Acipenser gueldenstaedtii♀ × Acipenser baerii♂) Resulting from Sodium Butyrate, Β-Glucan and Vitamin Supplementation

Background/Objectives: The effect of sodium butyrate (NaB), β-glucan (βG) and vitamins in the diet on gut microbiome, cortisol level, lysozyme activity and growth parameters of juvenile hybrid sturgeon (Acipenser gueldenstaedtii♀ × Acipenser baerii♂) was determined. Methods: Sturgeon hybrids (n = 144) were divided into three groups with enriched feeding (mg/kg of feed): FQV1 (50 NaB; 20 βG; const. vitamins), FQV2 (150 NaB; 20 βG; const. vitamins), FQV3 (50 NaB; 60 βG; const. vitamins) and control (not supplemented), each group in triplicate, 12 fish in each repetition. Rearing was carried out for 30 days in controlled conditions. Gut microbiome was characterized using Next Generation Sequencing (NGS) of DNA samples isolated from intestinal content. Cortisol level was determined using the ELISA test. Lysozyme activity was measured by turbidimetric test. Results: Based on data obtained from NGS, it was determined that the FQV1 group is characterized by the highest values of diversity indices (Shannon, Simpson and Chao-1) and the largest number of ASVs (Amplicon Sequence Variants). The highest abundance of probiotic bacteria (Lactobacillus, Lactococcus) was determined in the FQV1 group. The highest cortisol concentration was determined in the control (33.26 ng/mL), while the lowest was in FQV3 (27.75 ng/mL). The highest lysozyme activity was observed in FQV1 (154.64 U/mL), and the lowest in FQV2 (104.39 U/mL) and control (121.37 U/mL) (p < 0.05). FQV2 was characterized by significantly more favorable values of breeding indicators (p < 0.05). Conclusions: The obtained results prove that an appropriate composition of NaB, βG and vitamins can be used in the commercial breeding of juvenile hybrid sturgeons.

The effectiveness of sodium chloride for the treatment of Russian sturgeon (Acipenser gueldenstaedtii) caviar from saprolegniosis

The article presents the results of experimental work on the treatment of fertilized oocytes and developing embryos of the Russian sturgeon (Acipenser gueldenstaedtii) with 0,8% sodium chloride solution by various methods in order to suppress the growth and development of the family micromycetes sem. Saprolegniaceae, which cause saprolegniosis of eggs during factory incubation. Due to the intensive development of commercial aquaculture, an increase in the scale of artificial reproduction, as well as taking into account the limitations of the use of previously used veterinary drugs to combat saprolegniosis of incubated caviar, this research area is relevant. The purpose of the research work was to evaluate the effectiveness of using three different methods of treating caviar infected with micromycetes sem. Saprolegniacea with a solution of sodium chloride. Experimental work was carried out in factory conditions in the incubation apparatus «Sturgeon» under optimal hydrochemical conditions for the development of Russian sturgeon embryos. The experimental groups corresponded to the methods used (therapeutic baths and drip method in the apparatus, therapeutic baths outside the incubation system). The experiment was carried out in parallel in 2 repetitions in the presence of a control. In the course of the work, fish-breeding, biological and hydrochemical research methods were used. The effectiveness of the effect of sodium chloride solution by three different methods (drip method, therapeutic baths in an incubation apparatus of the «Sturgeon» type, short-term therapeutic baths outside the incubation system) on the embryonic development of sturgeon and micromycetes was assessed by such indicators as the percentage of fertilization of eggs, normally and abnormally developing embryos, hatched pre-larvae, the proportion of embryos infected with saprolegnium micromycetes at two stages of caviar development (stages 16 and 22). The most effective method that improves the fish-breeding and biological parameters of incubated Russian sturgeon caviar and reduces the extent of its invasion by family micromycetes sem. Saprolegniaceae is a drip method.

Current state of sturgeon fish off the eastern coast of the Sea of Azov

The aim: the characteristics of sturgeon fish that make seasonal migrations to the near-shore zone of the Azov Sea.Material — scientific monitoring of commercial fishing with stationary seines in the water area of the Sea of Azov adjacent to the Primorsko-Akhtarsk district in October 2022, 2023 and April 2023, 2024.The results: Russian Sturgeon and Starry Sturgeon (Sevruga) were encountered in stationary seines from 50% to 100%, and the average catch of these species per facility was 1.3–7 sp./day in the autumn and spring periods, respectively. In the fall of 2022, the prevalence of Sevruga in bycatch was almost double — 63% of the total bycatch; in the spring and fall of 2023, 2024, the superiority was with Sturgeon — 63–83% of the bycatch. Size range of Sturgeon in 2022–2024 was from 22 to 148 cm; Sevruga — from 23 to 123 cm. The weight range of Sturgeon was from 0.1 to 30.0 kg, Sevruga — from 0.2 to 7.8 kg. The share of fish that reached the commercial length was on average 20.7% of Sturgeon and 36.6% of Sevruga. The age of the fish varied from fingerlings to 16+ for Sturgeon and up to 8+ for Sevruga. The average fullness coefficient of Russian Sturgeon in the autumn was 0.72; in spring, — 0.79; Sevruga: in the autumn of 2022 and 2023–0.45, in the spring of 2023–0.58. The state of Russian Sturgeon in the near-shore aggregations indicates the formation of its full-fledged mixed-age population in the Sea of Azov, that allows to expect its commercial fishing in the near future, on the background of the increasing its stock. The state of the Sevruga requires more in-depth research. A high fish fatness coefficient indicates their sufficient food supply.Practical value: Observations of bycatch in stationary seines in the near-shore area of the sea are an important addition to the accounting trawl survey data for understanding the structure of the Russian Sturgeon population in the Azov Sea and practically the main source of information on the state of the Sevruga population.

Physiological research of young Russian sturgeons in modern ecological conditions of the Caspian sea

In the Volga-Caspian fisheries basin, artificial reproduction of sturgeon species is the primary source of replenishing their natural populations. The aim of this study is to conduct physiological research on juvenile Russian sturgeon (Acipenser gueldenstaedtii) in the western part of the Northern Caspian Sea, to establish the features of fish homeostasis. The physiological condition of the specimens was studied using a set of physiological and biochemical parameters. Hematological, biochemical, and morpho-histological parameters were evaluated. In the blood of the fish, the contents of hemoglobin, total protein, glucose, inorganic phosphorus, calcium, creatinine, bilirubin, total lipids, cholesterol, and triglycerides were determined. In the muscle tissue of juvenile Russian sturgeon, the physiological and biochemical indicators studied included the content of the main reserve substances of the body — total lipids and water-soluble protein. Histological methods were used to assess the morpho-functional state of the gills. The variability of physiological and biochemical parameters in juvenile Russian sturgeon was calculated using descriptive statistics based on parametric and non-parametric criteria in the blood and muscles. According to the results of correlation statistical analysis, significant changes were observed in the tissues of the sturgeon juveniles, aimed at providing the body with sources of energy and nutrients used for the functioning of body tissues and serving as reserve stocks, as well as maintaining regulatory mechanisms of metabolism and its changes depending on fluctuating environmental conditions. The morphological examination of the gills revealed vascular disorders, hyperplasia, swelling, and hypertrophy of the respiratory epithelium cells, corresponding to borderline disturbances from mild to moderate damage, which was the organ’s response to external environmental influences.

Application of feed enriched with humic additive from peat and dry garlic powder when growing juvenile Siberian sturgeon on an industrial line of cage aquaculture

Cage aquaculture, used in modern industrial sturgeon farming, differ from recirculating water supply systems (RAS) by more natural habitat conditions of fish growing, which are optimal for broodstocks development and maintaining and producing fish seeding material and is more economical. The dominant species for sturgeon aquaculture in Russia and throughout the world is Siberian sturgeon, Acipenser baerii Brandt, 1869, adapted to extreme temperature conditions. When this fish was grown at industrial cage aquaculture enterprises in the European North of Russia under natural conditions, the survival rate of the objects was 99%; growth rates exceeded those of sterlet, Russian sturgeon and F1 hybrids of Russian and Siberian sturgeon; the feed ratio was better compared to fish kept in cages in the Southern Federal District. Seven-year-old sturgeons reared in cages under such conditions had a maximum live weight of more than 8 kg, their physiological parameters were better than those of objects kept in a RAS; indices of reproductive system corresponded to the normal values. To increase the efficiency of keeping Siberian sturgeon in cage aquaculture in the extreme conditions of the Northern regions, feed enriched with multifunctional biologically active compounds of natural origin is used. In this production experiment, the basic forage included the feed additive Humiton of peat humic compounds origin at a dose of 25 ml/kg and/or dried garlic powder at a dose of 30 g/kg; both components previously have shown effectiveness in growing juvenile Siberian sturgeon under RAS conditions. In the experiment, all additives showed activity in all assessed indicators, but the greatest effect was observed when using garlic powder or its combination with Humiton additive. The effectiveness of additives is due to adaptogenic and immunomodulatory effects, the ability to favorably influence the function of the digestive system and improve the absorption of feed nutrients.

GWAS Enhances Genomic Prediction Accuracy of Caviar Yield, Caviar Color and Body Weight Traits in Sturgeons Using Whole-Genome Sequencing Data.

Caviar yield, caviar color, and body weight are crucial economic traits in sturgeon breeding. Understanding the molecular mechanisms behind these traits is essential for their genetic improvement. In this study, we performed whole-genome sequencing on 673 Russian sturgeons, renowned for their high-quality caviar. With an average sequencing depth of 13.69×, we obtained approximately 10.41 million high-quality single nucleotide polymorphisms (SNPs). Using a genome-wide association study (GWAS) with a single-marker regression model, we identified SNPs and genes associated with these traits. Our findings revealed several candidate genes for each trait: caviar yield: TFAP2A, RPS6KA3, CRB3, TUBB, H2AFX, morc3, BAG1, RANBP2, PLA2G1B, and NYAP1; caviar color: NFX1, OTULIN, SRFBP1, PLEK, INHBA, and NARS; body weight: ACVR1, HTR4, fmnl2, INSIG2, GPD2, ACVR1C, TANC1, KCNH7, SLC16A13, XKR4, GALR2, RPL39, ACVR2A, ADCY10, and ZEB2. Additionally, using the genomic feature BLUP (GFBLUP) method, which combines linkage disequilibrium (LD) pruning markers with GWAS prior information, we improved genomic prediction accuracy by 2%, 1.9%, and 3.1% for caviar yield, caviar color, and body weight traits, respectively, compared to the GBLUP method. In conclusion, this study enhances our understanding of the genetic mechanisms underlying caviar yield, caviar color, and body weight traits in sturgeons, providing opportunities for genetic improvement of these traits through genomic selection.

Polyculture of pikeperch (Sander lucioperca) and Russian sturgeon (Acipenser gueldenstaedtii) using an artificial common pellet – Implications on feed to fish nutrient transfers in recirculating aquaculture system (RAS)

The purpose of this research was to investigate the effects of monoculture and polyculture on the utilization of an artificial common pellet to produce nutritious products, specifically pikeperch and Russian sturgeon, in a recirculating aquaculture system (RAS) for 84 days. The experiment was conducted under controlled conditions, with specific parameters for: water temperature (21.8±0.4 °C), initial weight of the fish (pikeperch: 18.17±2.65 g; sturgeon: 18.23±3.62 g), volume of the containers (working volume of 272 litres) and feeding rate (1.5 %). Five experimental groups were tested in triplicates, including monoculture groups (pikeperch: 63.46±18.49 g; sturgeon: 93.52±50.40 g) and three polyculture combinations [P90: 90 % pikeperch (68.63±13.79 g) + 10 % sturgeon (86.10±33.38 g); P80: 80 % pikeperch (76.88±18.06 g) + 20 % sturgeon (103.53±44.60 g); P70: 70 % pikeperch (81.51±19.24 g) + 30 % Russian sturgeon (94.48±33.25 g)]. The results indicated that the addition of Russian sturgeon to pikeperch tanks could lead to efficient transfer of feed lipid to fish biomass through sturgeons, but not pikeperch. Polycultures showed better lipid absorption (P70 lipid-ADC 96.06±1.96 %) from the common pellet than monocultures (pikeperch: lipid-ADC 91.93±6.37 %; sturgeon: lipid-ADC 97.08±2.07 %). Fillet lipid content of pikeperch remained unaltered across RAS monocultures and polycultures but changed positively in Russian sturgeon in polyculture (P70 2.64±0.71 % > P0 1.75±0.75 %). In both species, polyculture fillets accumulated 5–7 % higher MUFA (oleic acid, C18:1n-9) than monoculture fillets. The major conclusions drawn from this research are that polyculture group P90 had both fish species flesh with highest muscle reserves of glycine and proline. In polyculture, critically indispensable muscle lysine reserves depleted in pikeperch, but Russian sturgeon muscle amino acid profile was stable. Given the global constraints on land availability, the study proposes RAS polyculture as a potentially productive and nutritious aquaculture system of the future. The research also suggests that resilient species for RAS polyculture need to be identified, proposing Russian sturgeon as a possible candidate.

Микроэлементный состав крови русского осетра

Establishing quantitative levels of chemical elements in the blood plays a leading role in studying the mi-croelement status of the body. The purpose of the work was to study the microelement composition of the blood and spleen of the Russian sturgeon Acipenser gueldenstaedtii (Brandt, 1833). The objects of the study were females and males of Russian sturgeon of different ages. The determination of metals was carried out using atomic absorption spectrometry. In each sample, iron, copper, manganese, zinc, nickel, cobalt, chromium, lead, and cadmium were determined. Specific features of the accumulation of chemical elements in the blood and spleen of Russian sturgeon have been revealed. The content of iron and zinc in the blood and spleen of fish is in the greatest quantities. At the same time, the concentration of zinc in the blood of fish, as well as the concentration of iron, depends on the systematic position of the fish, and falls within the limits of the concentrations of chemical elements according to A. P. Vinogradov: the content of iron and zinc in the blood of Teleostei is generally higher than in the blood of Elasmobranchii. Russian sturgeon belongs to the subclass Chondrostei and has characteristics of cartilaginous and bony fish, perhaps this can explain the amount of iron and zinc found in the blood. A positive correlation was revealed between iron and copper in the blood of female and male Russian sturgeon. At the same time, no gender differences were found in the content of chemical elements in the blood of female and male Russian sturgeon, with the exception of nickel, the concentration of which is higher in the blood of males. It has been shown that as fish age, the concentration of nickel, manganese, lead and copper in the blood increases.

Biokinetics of Americium-241 in the euryhaline diamond sturgeon Acipenser gueldenstaedtii following its uptake from water or food

Americium-241 whole body and internal biokinetics were experimentally investigated in the euryhaline diamond sturgeon Acipenser gueldenstaedtii during its uptake from water and food, in fresh (FW) and brackish water (BW; 9 psu). Whole-body uptake rates of 241Am from water and subsequent depuration rates were quantified over 14 and 28 days, respectively, and assimilation efficiency (AE) of 241Am from diet (chironomid) was determined over 28 days. FW reduced the biological half-life of 241Am following aqueous uptake by an order of magnitude. In contrast BW greatly reduced 241Am assimilation efficiency (AE) from diet (chironomid) by several orders of magnitude (from an AE of 8.5% (FW) down to 0.003% (BW)). Hence, salinity per se is indicated as a major environmental variable in determining the radiological exposure of A. gueldenstaedtii to 241Am. During aqueous exposure BW appreciably increased 241Am activity concentrations in most body components, but aqueous or dietary exposure pathway at either salinity did not determine marked differences in how 241Am was distributed among six body components. The highly mineralized skin of A. gueldenstaedtii recurred as a major repository of 241Am in all experimental treatments, as high as 50% among body components, due to its internal transfer from diet, surface adsorption and/or active absorption from water. The indicated prominence of the aqueous, compared to the dietary, exposure pathway for 241Am accumulation by A. gueldenstaedtii suggests its radiological exposure would be enhanced by BW as it leads to its greater long-term retention, due to a much longer biological half-life.

Multi-omics combined approach to analyze the mechanism of flavor evolution in sturgeon caviar (Acipenser gueldenstaedtii) during refrigeration storage

Multi-omics techniques were combined with microstructure, molecular sensory science and non-volatile matrices for the first time to investigate variations in organic macromolecules and flavor in caviar during preservation. After 4–6 weeks of storage, the peroxide value was 35.38 mg/g and the accumulation of thiobarbiturates was significant with caviar membranes exhibiting a decrease in elasticity and an increase in viscosity. Sixteen key volatile compounds were detected by GC–MS, while the volatile compounds that contributed to the differences in caviar flavor at different storage times were mainly tetradecane, (E)-2-hexenal, and heptanal. The pathways associated with flavor release during storage were mainly abundant in the linolenic acid metabolism, alanine metabolism, and glycerophospholipid metabolism pathways. The correlation of 11 differential proteins and 24 differential lipids with odorants was further explored, such as arginine, proline, alanine, PE (20:4/22:6), PE (16:1/18:2), and PE (20:5/18:2). Overall, Aspartate, glutamate, oleic acid, linoleic acid, and phospholipids enriched in C22:6 and C18:2 chains are potential metabolic markers. This study provides a basis from a multi-omics perspective for the investigation of the relationship between quality deterioration and precursor metabolism in caviar storage process.

Genotoxic effects in blood cells of sturger (Acipenseridae) grown in conditions of cage farming of the Volga delta, Russia

The purpose of this work was to assess the degree of genotoxic influence of the habitat on individuals of Russian sturgeon and sterlet raised in cage farming conditions in the Volga delta, using micronucleus and DNA comet tests.The blood of the individual Russian sturgeon and sterlet was shaved off during their lifetime. A comet DNA test was performed using the alkaline method. The number of erythrocytes with micronuclei was determined microscopically. To assess the physiological state of sturgeons, conventional hematological and biochemical methods were used.In the samples of fish blood smears studied, the average proportion of erythrocytes with micronuclei was 3.20 ± 1.24 ‰ in Russian sturgeon and 5.25 ± 1.18 ‰ in sterlet. The proportion of DNA in the comet tail in erythrocytes of Russian sturgeon was 3,99 %, and in sterlet 6, 48 %. The values of tail moment and Olivet moment were also lower in Russian sturgeon. Among sterlet erythrocytes, a more heterogeneous pattern of DNA damage can be noted. The length of the comet tail in starlet individuals turned out to be lower than in Russian sturgeon: apparently, larger fragments of these molecules were formed when the DNA of starlet erythrocytes was damaged. The physiological state of sterlet individuals can be characterised as normal, and that of the Russian sturgeon as satisfactory, due to the deviations identified in the values of some hematological and biochemical blood parameters.Having studied the influence of the environment on individual sturgeon kept in cage aquaculture conditions in the Volga delta using micronuclear and DNA comet tests, we can conclude that there was no acute genotoxic effect at the time of the study.

Genetic health and diversity assessment of Sturgeon species in Kazakhstan's aquaculture and natural habitats

Sturgeon species hold significant commercial and ecological value, with many listed as endangered. Understanding their genetic structure is crucial for developing effective conservation strategies. The main aim of this study is to examine the genetic structure of sturgeon, which can provide a foundation for creating strategies to conserve these species. A total of 121 sturgeon individuals were analyzed using microsatellite molecular markers (STR) to conduct the study on the genetic structure of sturgeon fish species. DNA was extracted from fin tissues using a commercial kit, and genotyping was conducted using seven microsatellite loci. Cluster analysis and principal coordinates analysis (PCoA) were performed to identify genetic differentiation among populations. The analysis showed differences in genetic diversity between the Siberian sturgeon, Russian sturgeon, and beluga samples. A deficiency of heterozygotes was discovered in artificial samples of sturgeon, indicating possible inbreeding. Genetic analysis has also revealed genetic differentiation between populations, possibly due to geographic structure or other factors. The study allows us to recommend increasing genetic diversity by introducing individuals from natural environments into sturgeon populations in aquaculture. Regular monitoring of genetic parameters in aquaculture populations and monitoring diversity dynamics are also crucial for the conservation and sustainability of sturgeon populations. The findings could help shape conservation strategies, especially in managing genetic diversity in aquaculture and reducing the risks associated with inbreeding and genetic drift.

Effect of bicultural rearing of pikeperch (Sander lucioperca) and Russian sturgeon (Acipenser gueldenstaedtii) on growth and fish condition parameters in RAS

This study investigated the intensive rearing of pikeperch (Sander lucioperca) and Russian sturgeon (Acipenser gueldenstaedtii) in a recirculating aquaculture system for 84 days, with five different stocking ratios (with P as a percentage of pikeperch): P100, P90, P80, P70, and P0. The growth parameters, fish condition parameters, and blood biochemistry were measured. The P70 group showed the highest final total length, standard length, and body weight of pikeperch (82.95 ± 18.92 g), while the lowest values were found in Groups P100 (63.46 ± 18.49 g) and P90 (68.63 ± 13.79 g). The sturgeon did not show significant differences, except for Group P90, which had the lowest body weight (86.10 ± 33.95 g). Survival rates were high for pikeperch (96.098.6%) and no mortality in the sturgeon was evident in all groups. The feed conversion ratio (FCR) for pikeperch was similar between Group P100 (0.88 ± 0.02) and the two bicultural groups P90 (0.80 ± 0.04) and P80 (0.69 ± 0.05). For the sturgeon in Group P0, had a comparable FCR (0.71 ± 0.13). The lowest FCR for sturgeon was observed in the bicultural group P70 (0.66 ± 0.03). Tissue-somatic indices, hepatosomatic index (HSI), and fat-somatic index (FSI), supported significant differences only for pikeperch, with the highest values for the P80 and P70 groups. This study of pikeperch and Russian sturgeon rearing in various stocking ratios for 84 days demonstrates optimal growth and health parameters in the P70 group for pikeperch, with overall high survival rates and minimal health variations in sturgeon, suggesting the effectiveness of a mixed species approach in recirculating aquaculture systems.

Investigation of Sexes and Fertility Potential of Female Russian Sturgeon (Acipenser gueldenstaedtii) and Male American Paddlefish (Polyodon spathula) Hybrids.

In the present study, 10 allotriploid (3nALT) and 10 allopentaploid (5nALP) six-month-old hybrid fish and two 3nALT and four 5nALP 40-month-old hybrid fish, which resulted by crossing female Russian sturgeon Acipenser gueldenstaedtii (Brandt and Ratzeberg, 1833) and male American paddlefish Polyodon spathula (Walbaum, 1792), were investigated. It was revealed that six-month-old 3nALT and 5nALP hybrids initially had "undifferentiated" gonads, while in the 40-month-old hybrids, only testes were observed in one case of 3nALT and one case of 5nALP hybrids. The testis of 3nALT hybrids was partially developed with spermatogonia, while the testis of one 5nALP hybrid was in the second developmental stage with low spermatogonia density. We could not determine gonad differentiation in any of the cases when the hybrid individuals had the W sex chromosome. We concluded that the gonad differentiation of these interfamilial hybrids follows a similar pattern to interspecific hybrids of different ploidy parent species of the family Acipenseridae, which is consistent with the classical Haldane's rule. However, it cannot be excluded that the testis of this/these hybrid(s) may produce fertile sperm after sexual maturity, depending on additional genetic, hormonal and environmental factors, and further research is required for its evaluation.

A complete study of neuroendocrine regulation of fish reproduction. 4. Migration impulse as a starting mechanism of spawning

The participation of the hypothalamo-hypophysial neurosecretory system (NS) in the initiation of anadromous fish spawning migration was established on the basis of ecological-histophysiological analysis the results of histomorphological, immunohistochemical and electron microscopic studies for the first time. Activation of the neurosecretory products synthesis in the neurosecretory cells perikaryons and their excretion into the cerebrospinal fluid of the III brain ventricle in anadromous migrants forms at the beginning of the river spawning migration, spring-spawning: Russian sturgeon, stellate sturgeon and autumn-spawning: pink salmon and chum salmon, was shown. Transport and mass accumulation of neurosecretory products in the neurohypophysis were discovered at the same time. It is concluded, that the NS impacts a complex synchronous effect, which consists: firstly, in the neurotropic effect of nonapeptide neurohormones (NPh) on behavioral centers, which causes a dominant state of CNS excitation corresponding to the “Migration impulse”; secondly, in the violation of the long-term adapted marine “Pastured” level of osmoregulation; and thirdly, in the cessation of the well-known antigonadotropic effect of NPh, which contributes the organism transition to the energyconsuming energy type of metabolism. A comparative analysis (cross-analysis) of our own and literature data confirms the commonality and points to the universality of this metabolic mechanism for different forms of migration in fish ontogeny, which allows us to consider it as the most important aromorphosis type of phylogenetic adaptations, aimed at the species biological progress achieving. In the subsequent navigational mechanisms of homing, widely covered in the world literature, the leading role is played by the luliberinergic centers of the hypothalamus. The ecological diversity of these population-level mechanisms and the presence of straing in fish allow us to consider them as specializations of microevolutionary origin. The most promising direction for the further neuroendocrinological research development seems to be the analysis of the mechanisms of imprinting in connection with the enhancement of growth and survival of juveniles in the critical salinity medium, and for the purpose of homing control (development of the commercial fish-return biotechnology management) — the mechanisms of interaction between the NS and the luliberinergic centers in the neuroendocrine complex of CNS.

Anadromous sturgeon fish of the Azov Sea under conditions of natural and anthropogenic transformations of the water ecosystem

The aim: assessment of the state of populations of anadromous sturgeon in the Sea of Azov, the efficiency of their reproduction and the possibility for the existence of populations in the medium term until 2030–2040. Methods: the calculation of the biomass and population size of sturgeon in the Sea of Azov was carried out using the direct counting method and a modified cohort solution of the Baranov equation. 18and 25-meter bottom trawls were used as standard fishing gear. The assessment of the number of juvenile sturgeon in the Don River was carried out with 3and 2-meter beam-trawls. Molecular genetic methods for the analysis of microsatellite loci and sequencing of a fragment of the control region of mitochondrial DNA were used.Novelty: materials are presented on natural reproduction of sturgeon in the Don River after flow regulation, and the rate of decline in the survival rate of generations of Russian sturgeon and stellate sturgeon under the influence of illegal fishing is shown. Based on the results of a study of the genotypes of Russian sturgeon individuals, migrations sturgeon from Azov to the Black Sea, as well as Black Sea populations to the Sea of Azov, were confirmed.Results: an analysis of the dynamics and current state of anadromous sturgeon in the Sea of Azov is presented under the conditions of anthropogenic transformation of their habitat, loss of natural reproduction and climate-related fluctuations in the salinity of the sea waters. A retrospective overview of their commercial use from the mid-19th century to the present is given. The prospects for restoring commercial stocks of sturgeon fish are considered.Practical significance: the possibility of restoring commercial stocks of sturgeon in modern conditions is shown by increasing the number of released juveniles and increasing the effectiveness of fish conservation measures to a level of more than 90 thousand tons and creating an commercial population of sturgeon in the Sea of Azov.