Sturgeon Species Research Articles

Effects of Different Carbon Sources on Growth and Some Innate Immune Responses of Russian Sturgeon (Acipenser gueldenstaedtii) in Biofloc Systems

The Russian sturgeon (Acipenser gueldenstaedtii) species is in high demand owing to its valuable caviar. Therefore, it is in danger of extinction. Since the Russian sturgeon reaches sexual maturity late in its life cycle, this species has a high economic cost for farmers. However, this high cost can be reduced with an environmentally friendly system called biofloc technology. This study compared the growth performance and health indicators of biofloc groups using different carbon sources such as starch (BS), molasses (BM) and dextrose (BD). In the 60-day study, fish with an average initial weight of 106.44±5.79 g were stocked in tanks at a density of 21 fish/tank (0.4 m3/tank). The water temperature was set at 19 ℃ degrees throughout the study. On the 30th and 60th days of the experiment, fish were weighted to measure the growth parameters and sampled for immune indices. No mortality was observed in any group throughout the study. A between group comparison of weight gain revealed that BS and BM (105.51±2.26; 100.50±2.18) performed better than the control (BC, without external carbon sources) and BD groups (95.90±2.09; 87.36±2.18) (P<0.05). Furthermore, FCR and SGR were calculated from the data obtained at the end of the experiment, and the data shows that the BS and BM groups were statistically more effective than the other groups. Moreover, a comparison of NBT, lysozyme and myeloperoxidase enzyme activities indicated that all BFT groups had a stronger immune system than the control group (P<0.05). According to the results, the immune-enhancing effect of BFT for sturgeon was determined, and it was reported that BS and BM are more suitable for use in this species in terms of FCR and SGR, as they result an economic and environmentally friendly production.

Species Identification of Caviar Based on Multiple DNA Barcoding.

This study aimed to explore the applicability of DNA barcoding for assessing the authenticity of caviar on the Chinese market. A set of universal COI primers and two sets of designed primers based on COI and D-loop genes were used to identify maternal species of samples from 21 batches of caviar. The results showed that the PCR products from three sets of primers had more than 98% similarity to the sequences in database. The COI gene could not distinguish sturgeons with closed genetic relationships, while D-loop gene could effectively improve the accuracy of DNA barcoding and was more suitable to the identification of interspecific sturgeon than the COI gene. The neighbor-joining dendrogram further confirmed the applicability and accuracy of COI and D-loop genes in identifying maternal relatives of caviar (Acipenser baerii/Acipenser gueldenstaedtii/Acipenser schrenckii/Huso dauricus/Huso huso). Despite the limitations of mitochondrial DNA in identifying hybrid sturgeon species, the presence of counterfeit caviar of non-sturgeon ingredients could be excluded. All the caviar samples were identified successfully as sturgeon species, but the mislabeling rate of species was 33.4%, indicating that there were illegal phenomena such as disorderly labeling, mislabeling, and adulteration on the market.

Studies of fish breeding biological and genetic parameters of stellate sturgeon (Acipenser stellatus Pallas, 1771) offspring obtained using native and cryopreserved sperm

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.

Исследование физико-механических и химических свойств комбикормов с погонами дезодорации для осетровых рыб

Breeding sturgeons in aquaculture is the only way to preserve them as a raw material for fish food products today. In this regard, not only the need for the development of commercial sturgeon breeding is obvious, but also the importance of research aimed at studying and developing optimal modes of industrial cultivation of different species of sturgeon. The aim of the work is to expand the range of compound feed for sturgeons, at the expense of unused reserves for expanding the food base, which are by-products of the oil and fat industry, in particular, deodorization cuts. Based on the study of the classical technology for obtaining feed for valuable fish species and eliminating its shortcomings, a technology has been developed for the production of pseudo-encapsulated feed with a content of more than 20% fat in it and vitamins adapted for various types of sturgeons grown in the Central Federal District of the Russian Federation. In the proposed technology for the production of feed for valuable fish species, pseudocapsulation of granules with fat absorbers with oil and fat waste, for example, deodorization cuts, is carried out in a plate granulator. On the basis of the studies performed, it was found that in order to introduce an increased fat content of deodorization cuts (more than 20%) into the composition of pseudoencapsulated compound feed, it is necessary to use fat absorbers, which can be recommended as silicon dioxide aerosil. When using silicon dioxide aerosil, it is possible to ensure the inclusion of up to 20-30% fat of deodorization cuts in the feed composition in a ratio of 1:4, without worsening the technological properties of the finished product.

InDel DNA Markers Potentially Unique to Kaluga Sturgeon Huso dauricus Based on Whole-Genome Resequencing Data

Sturgeons are ancient and endangered species whose populations have been greatly reduced over the past few centuries due to habitat destruction and overfishing for the production of expensive caviar. All sturgeon species are listed in CITES Appendix II to limit their trade; therefore, accurate species identification is crucial. In this study, we performed whole-genome resequencing of five sturgeon species, including Kaluga sturgeon (H. dauricus), Siberian sturgeon (A. baerii), Sterlet sturgeon (A. ruthenus), Russian sturgeon (A. gueldenstaedtii), and Amur sturgeon (A. schrenckii), to obtain species-specific InDel-based nucleotide sequences for Kaluga sturgeon. Through whole-genome screening within these five sturgeon species, we developed methods for the rapid identification of Kaluga sturgeon germplasm. Using dominant/co-dominant molecular markers designed for Huso dauricus, purebred or hybrid samples can be identified through a PCR reaction. These markers allow for the precise identification of Kaluga sturgeon lineages from at least seven sturgeon species (H. dauricus, A. schrenckii, A. ruthenus, A. baerii, A. gueldenstaedtii, A. stellatus, and H. huso) and their hybrids. This development is expected to have a positive effect on both the sturgeon trade and the conservation of sturgeon germplasm resources.

Siberian and Russian sturgeon natal origin in South America: Fish farm or established population?

AbstractSturgeon (Acipenser baerii and A. gueldenstaedtii) specimens, native to the northern hemisphere, were reported in different environments of the La Plata Basin (South America). The objectives of this study were to provide the first insights into the natal origin and habitat use of these sturgeon species in the La Plata Basin through geochemical analysis (87Sr/86Sr) of fin spines and to review historical catch reports. Spine core‐to‐edge 87Sr/86Sr ratios were measured by LA‐MC‐ICPMS. A Quadratic Discriminant Analysis model based on water 87Sr/86Sr baseline of the La Plata Basin was run to infer the natal origin. The isotopic profiles indicate a common origin, compatible with the location of the fish farms in the Uruguay Basin. The A. baerii isotopic time series suggested that the fish moved towards the Paraná Basin months before capture, while A. gueldenstaedtii would have survived a longer time (perhaps years). Seventeen reports of sturgeons were recorded and preserved in museum collections between 1998 and 2020. Sturgeons were collected from Río de la Plata Estuary, Paraná and Uruguay basins and Atlantic coastal lagoons. It is recommended to closely monitor sturgeon catches, paying special attention to the appearance of specimens of reproductive age, in order to generate management and management plans if necessary.

Genetic monitoring of sterlet juveniles (Acipenser ruthenus) in the Volga river

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).

Factors affecting the tolerance of sturgeon species to hypoxia (review)

Factors affecting the tolerance of sturgeon species to hypoxia (review)

Conservation Status and Effectiveness of the National and International Policies for the Protection and Conservation of Sturgeons in the Danube River and Black Sea Basin

Rivers and their watersheds have been subject to various changes, including biodiversity, caused by anthropogenic activities. The Danube River and Black Sea basin overlap the geographic range of six species of anadromous fish belonging to the family Acipenseridae. Nowadays, they are endangered or at risk of extinction in the wild due to fragmentation and destruction of natural habitats, blocking their migration to spawning grounds, water pollution, and poaching. This paper presents a review of the historical and current distribution and evolution of the sturgeon populations of sturgeon species in the Danube River basin. Conservation status and measures for species protection, conservation, and restoration at the national, regional, and global levels are presented.

Regulation of antioxidant defense in response to heat stress in Siberian sturgeon (Acipenser baerii)

Siberian sturgeon (Acipenser baerii) is one of the most important breeding species of sturgeon in the world. The objective of the present study was to assess the effect of short-term gradual heating up (1 °C/8 h) and recovery changes on antioxidant defense systems in the liver, kidneys, gills, and serum of the Siberian sturgeon, and to examine related gene expression levels and histological changes in the liver and gills. When the water temperature reached to 33 °C (about 88 h), LOE (loss of equilibrium) appeared in individuals. Heat stress affected the metabolic mode and oxidative stress parameters in a tissue-dependent manner. Expression of HSP family genes such as heat shock cognate 70 (hsc70), heat shock protein 70 (hsp70), and heat shock protein 90 (hsp90) were elevated in the liver and gills of two heating groups, and these returned to normal levels after 24 h of recovery. Hsf1 expression was not significantly different between the control and heating groups, but was lower in the liver and higher in the gills after 24 h recovery. Heat stress resulted in clear histological changes in the liver, including the hepatic lobules, showing vacuolization and loss of cell boundaries and asymmetric shapes; the gills showing increasing numbers of vacuoles, thinning of basal cells, epithelial cell denaturation, degeneration, and necrosis. After 24 h of recovery, the liver and gills in the active group recovered better than those in the LOE group. Of four antioxidant enzymes (superoxidase dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH), glutathione peroxidase (GPX)), only LDH activity varied significantly, decreasing in the liver, increasing in the kidneys of heating groups, and recovering to control levels after 24 h. Total antioxidant capacity (T-AOC) also did not change significantly in the three tissues. Both plasma cortisol and lactate were significantly influenced by thermal stress, and returned to control levels within 24 h. MDA (malondialdehyde) remained at a relatively stable level after heat stress and recovery. Rapid cooling after enduring heat stress allowed the Siberian sturgeon to recover quickly. After 24 h of recovery, nine LOE and eleven active recovery individuals were alive and able to feed, accounting for 32.7% and 36.5% of the experimental groups, respectively. These results indicate that Siberian sturgeon not only has a strong antioxidant system and adaptive capacity to short-term gradual heating, but also has the capacity to quickly recover from heat stress, with physiological parameters returning to pre-stress levels after 24 h.

Physicochemical and Biochemical Properties of Trypsin-like Enzyme from Two Sturgeon Species.

This work aimed to determine the physicochemical and biochemical properties of trypsin from beluga Huso huso and sevruga Acipenser stellatus, two highly valuable sturgeon species. According to the results obtained from the methods of casein-zymogram and inhibitory activity staining, the molecular weight of trypsin for sevruga and beluga was 27.5 and 29.5 kDa, respectively. Optimum pH and temperature values for both trypsins were recorded at 8.5 and 55 °C by BAPNA (a specific substrate), respectively. The stability of both trypsins was well-preserved at pH values from 6.0 to 11.0 and temperatures up to 50 °C. TLCK and SBTI, two specific trypsin inhibitors, showed a significant inhibitory effect on the enzymatic activity of both trypsins (p < 0.05). The enzyme activity was significantly increased in the presence of Ca+2 and surfactants and decreased by oxidizing agents, Cu+2, Zn+2, and Co+2 (p < 0.05). However, univalent ions Na+ and K+ did not show any significant effect on the activity of both trypsins (p > 0.05). The results of our study show that the properties of trypsin from beluga and sevruga are in agreement with data reported in bony fish and can contribute to the clear understanding of trypsin activity in these primitive species.

Effects of Kisspeptin on the reproductive function in the Dabry’s sturgeon (Acipenser dabrynus)

Kisspeptin, a kind of neuropeptide, is involved in various physiological processes such as tumor metastasis inhibition and reproductive regulation due to its ability to interact with Kisspeptin receptor-Kissr. In teleost, Kisspeptin/Kissr system stimulates the hypothalamus-pituitary–gonadal axis (HPG axis), which is crucial for the reproductive regulation. Compared to one Kisspeptin protein Kiss1 was existed in mammals, two Kisspeptin were identified in sturgeon species, including Kiss1 and Kiss2, with specific receptors of Kissr1 and Kissr2, respectively. However, few reports described the effects of the two isoforms of Kisspeptin on the reproductive regulation in sturgeon. The core peptides of Kiss1 and Kiss2 (Kiss1-10 and Kiss2-10) of Dabry’s sturgeon were successfully synthesized to explore the functional influence of Kisspeptin on the sturgeon HPG axis in the present study. The present findings suggested that intraperitoneal injection of Kiss1-10 and Kiss2-10 could significantly up-regulate the mRNA expression of Gnrh、Fsh and Lh in the hypothalamus and pituitary and the content of Lh protein in the serum. Assays of Kisspeptin-treated cells demonstrated that Kiss1-10 and Kiss2-10 can significantly promote the expression of Gnrh in hypothalamus cells and Lh and Fsh in pituitary cells of Dabry’s sturgeon, indicating their direct-acting effect on pituitary cells and regulatory function on the reproductive development of sturgeon. This study described the reproductive function of the Kisspeptin in the Dabry’s sturgeon for the first time, and provided supportive reference for the development of high-efficiency ripening technologies of artificially breeding sturgeon.

Eating Sturgeon: An Endangered Delicacy

Since ancient times, sturgeon species have been valued for their rich nutritional qualities, which are crucial for human health today. They are linked with gastronomic delicacy and offer economic benefits, especially for the caviar industry. Today aquaculture produces more farmed and hybrid species due to rapidly declining wild sturgeon populations. Sturgeon diversification through processing can yield fingerlings, stocking material, meat or caviar. Because of its variety, sturgeon flesh includes highly digestible proteins, lipids, vitamins and minerals. Consuming sturgeon provides essential fatty acids that play important oxidative and anti-inflammatory roles in human cells. The purpose of this study is to examine the sustainability and economic value of eating sturgeon worldwide, the technology applied in food processing, and the challenges that food quality and authenticity, nutritional content and health effects pose. The issue of counterfeiting high-quality sturgeon products by dishonest means has to be adequately addressed. Digital tools to guarantee authenticity and transparency in the sturgeon value chain should be considered in the future.

Atlantic sturgeon and shortnose sturgeon exhibit highly divergent transcriptomic responses to acute heat stress

In comparison to most modern teleost fishes, sturgeons generally display muted stress responses. While a muted stress response appears to be ubiquitous across sturgeon species, the mechanisms unpinning this muted response have not been fully described. The objective of this study was to determine the patterns of hematological and transcriptomic change in muscle tissue following an acute high temperature stress (critical thermal maxima; CTmax) in two locally co-occurring but evolutionarily distant sturgeon species (Atlantic and shortnose sturgeon). The most striking pattern found was that Atlantic sturgeon launched a vigorous transcriptomic response at CTmax, whereas shortnose sturgeon did not. In contrast, shortnose sturgeon have significantly higher cortisol than Atlantics at CTmax, reconfirming that shortnose have a less muted cortisol stress response. Atlantic sturgeon downregulated a number of processes, included RNA creation/processing, methylation and immune processes. Furthermore, a number of genes related to heat shock proteins were differentially expressed at CTmax in Atlantic sturgeon but none of these genes were significantly changed in shortnose sturgeon. We also note that the majority of differentially expressed genes of both species are undescribed and have no known orthologues. These results suggest that, while sturgeons as a whole may show muted stress responses, individual sturgeon species likely use different inducible strategies to cope with acute high temperature stress.

Methodology for Identification of Areas with Possible Risk for Sturgeon Species Migration Disruption on The Lower Danube

In the context of the continuing decline of the species belonging to the order Acipenseriformes on a global level, the anadromous sturgeon species sturgeon species in the Lower Danube have been affected by a significant reduction in historical migration routes and fragmentation of breeding habitats. This paper presents the stages of the methodology for identifying areas that present a possible risk of interruption of sturgeon migration in correlation with satellite images and daily values for discharge/water level databases. In order to determine the two ranges of values that characterize the extreme phenomena (high/low flows), a hydrological statistical analysis was carried out for the most extensive period of time covered by recorded data (January 2011 – May 2023) in the hydrometric station located in Calarasi, Romania. Based on the 4524 values from the series of average daily discharge values, the discharge hydrograph, the empirical curve of insurance/exceedance probability and the frequency and duration curves using 200 m3/s discharge steps were determined and represented. Correlated with satellite imagery recorded during the determined time intervals with extreme phenomena, there were identified areas with possible risk for sturgeon species migration disruption.

CAVIAR THE GOLD IN YOUR SPOONA

Caviar is the unhatched roe of certain species of sturgeon and is used as an appetiser around the world. Caviar is famous for a number of reasons, most notably its exorbitant cost and its salty, nutty, and luscious flavour.Over the past 30 years, natural sturgeon populations have declined dramatically, and a rising demand for caviar has prompted the development of sturgeon farming for the production of caviar.Caviar passes through a lengthy procedure from fish to plate. Beluga, Sterlet, Kaluga hybrid, Ossetra, Siberian sturgeon, and Sevruga are the most popular forms of caviar produced by sturgeon species indigenous to the Caspian Sea.Premium caviar is extremely perishable.Typically sold in vacuum-sealed containers, premium caviar lasts 2-4 weeks unopened.caviar has always been a "meal of the privileged," and appropriately so. Pearl- sized pearls erupt in the mouth and taste fishy. Yet, caviar was previously a luxury. Historically, Russian fishermen ate caviar. Caviar on top of hot, cooked potatoes was a staple. Russian fishermen call caviar "roe".It has abundant usage in the culinary world. Including health benefits selenium is abundant in caviar and acts in tandem alongside vitamin E to prevent free radical damage to cells.Caviar's omega-3 fatty acids improve mood and cognition, making it a popular treatment for depression and bipolar illness.

The presence of Acipenser sturgeons in the Iberian Peninsula: a review of the existing literature

The conservation status of sturgeon species is highly alarming. Six of the European Acipenser species are critically endangered. Several studies developed in the last decades have analysed the distribution of sturgeons in the Iberian Peninsula, questioning the possibility of the native character of some Acipenser species there, with a special focus on the Adriatic sturgeon, A. naccarii. We review the available knowledge on the distribution on Iberian Acipenser sturgeons, in order to ascertain their nativeness status, as a necessary tool to implement measures for their management and conservation. One vagrant specimen of A. oxyrinchus, and several released or escaped specimens of A. baerii and A. naccarii have been recorded in the Iberian Peninsula. Our results show that the Atlantic sturgeon A. sturio is the only native sturgeon species that has had breeding populations in the past in the Iberian Peninsula. Regarding A. naccarii, further evidence is required to prove its dubious native character in the Iberian Peninsula. Although the reviewed studies have solidly shown that A. naccarii has been present outside the Adriatic basin, the presence of isolated individuals does not constitute sufficient evidence to sustain the existence of past breeding populations.

Validation of a microwave energy meter to non-lethally estimate energetic reserves in adult sturgeon.

Whole-body (WB) energetic reserves influence fish survival, growth, and reproduction but are typically quantified using lethal methods (i.e. proximate analyses) or interpreted through body condition indices. Energetic reserves can impact population dynamics through influences on growth rates, age-at-first-reproductive-maturity, and spawning periodicity at the individual-fish level, especially in long-lived sturgeon species. Therefore, a non-lethal tool to track the energetic reserves of endangered sturgeon populations could inform adaptive management and further our understanding of the sturgeon's biology. The Distell Fatmeter is a microwave energy meter that has been validated to non-lethally estimate energetic reserves in some fish species, but never successfully for sturgeon. Here, stepwise linear regressions were applied to test commonly monitored body metrics and Fatmeter measurements at nine different anatomical sites on captive adult pallid sturgeon (Scaphirhynchus albus; total length of 790-1015mm; WB lipid of 13.9-33.3%) compared with WB lipid and energy content determined by proximate analyses. Fatmeter measurements alone explained approximately 70% of the variation in WB energetic reserves, which outperformed models considering body metrics alone by a margin of approximately 20%. The top-ranked models based on AICc score (second-order Akaike Information Criterion) included a combination of body metrics and Fatmeter measurements and accounted for up to 76% of the variation in WB lipid and energy. We recommend the incorporation of Fatmeter measurements at a single site located dorsally to the lateral scutes at the posterior end of the fish above the pelvic fins (U-P) into conservation monitoring programs for adult pallid sturgeon (total length [TL] ≥ 790mm; fork length [FL] ≥ 715mm) and the cautious application of Fatmeter measurements for sturgeon between 435 and 790mm TL (375-715mm FL). Measurements at this U-P site combined with body mass explained approximately 75% of the variation in WB lipid and energy.

ВЫПУСК МОЛОДИ ОСЕТРОВЫХ В АЗОВО-КУБАНСКОМ РАЙОНЕ С РЫБОВОДНЫХ ЗАВОДОВ ФЕДЕРАЛЬНОГО АГЕНТСТВА ПО РЫБОЛОВСТВУ В ПЕРИОД С 2016 ПО 2022 Г.

Background. By the end of the 20th and the beginning of the 21st century, artificial reproduction had taken up a key role in the sturgeon stock recruitment in the natural water bodies of the Azov–Kuban region. Relevance. The major part of artificial reproduction of sturgeon species is conducted in the fish hatcheries of the Azov–Kuban region under the authority of the Federal Agency for Fishery (Rosrybolovstvo). The aim of this study was to analyze the volumes of rearing and release of juvenile sturgeons into water bodies of fisheries importance in the Azov–Kuban region by fish hatcheries subordinate to the Federal Agency for Fishery. Methods. This article is based on the data recordings of the Azov-Black Sea Branch of the FSBSI “VNIRO” (“AzNIIRKH”) for the time range from 2016 through 2022. The data on 4 sturgeon hatcheries— Adygea, Achuevo, Grivensk, and Temryuk—are presented and analyzed. Results. An increase in the total number of juveniles of sturgeon species released into the natural habitat has been revealed. The highest values were recorded in 2021–2022. There has also been a disproportion in the number of released juveniles belonging to different species. Each year, sterlet Acipenser ruthenus accounted for a large share of released juveniles, for which the percentage ranged from 47.6 % in 2018 to 64.4 % in 2022. In recent years, the volumes of rearing and releasing the juveniles of this species have been increasing both quantitatively and in percentage terms. This fact can be explained by the earlier maturation of sterlet breeders, shorter intervals between repeated spawning, and the resultant larger number of “active” breeders of this species in the hatcheries. From 2019 through 2022, the share of the juveniles of sturgeon species released by the hatcheries of the Federal Agency for Fishery into the Protoka River, as compared to the Kuban River, increased from 55.0±0.10 % in 2016–2018 to 68.9±0.44 % (2019–2022). It resulted from the increase in the number of the sturgeon juveniles released into this water body, and not from a redistribution of release volumes between the Kuban and Protoka Rivers. Conclusion. In general, the artificial reproduction of sturgeon species by the fish hatcheries of the Federal Agency for Fishery in the Azov–Kuban Basin has shown a positive dynamics. However, it has also been found necessary to increase the scale of artificial reproduction of the most commercially valuable anadromous species: Russian sturgeon Acipenser gueldenstaedtii and stellate sturgeon Acipenser stellatus.

РЕЗУЛЬТАТЫ ИССЛЕДОВАНИЙ АЗОВСКИХ ПОПУЛЯЦИЙ ОСЕТРОВЫХ РЫБ ПРИ ОСУЩЕСТВЛЕНИИ МОНИТОРИНГА ПРОМЫСЛА СТАВНЫМИ ОРУДИЯМИ ЛОВА У КУБАНСКОГО ПОБЕРЕЖЬЯ

Introduction. After depletion of the Russian sturgeon Acipenser gueldenstaedtii Brandt &amp; Ratzeburg, 1833 and stellate sturgeon Acipenser stellatus Pallas, 1771 stocks at the end of the 20th century, their abundance in the Azov and Black Sea Basin has been maintained through the release of the juveniles obtained by the means of artificial reproduction. Resulting from the strengthening protection of the aquatic living resources and gradually increasing number of the released juveniles, since 2014, as evidenced by the research studies, an increase in the population abundance of these fish species and their biomass is observed in the Azov Sea (from 42 t in 2015 to 998 t in 2022). Unstable state of the sturgeon populations in the coastal waters of the Azov Sea predicated the relevance of this work. Its aim was to investigate the distribution and age–length composition of the populations of the sturgeon fish species in the coastal waters of the Azov Sea. Methods. This study was based on the data on age–length composition collected over the course of the investigation of sturgeon by-catches in stationary pound nets in the coastal waters of the Azov Sea within an administrative unit Primorsko-Akhtarsky District (Yasensk and Achuevo Spits). According to its results, out of all sturgeon species, in the autumn season, the stellate sturgeon prevailed—53 %; the share of Russian sturgeon was 43 %, and for beluga sturgeon, it was 4 %. In summer, the Russian sturgeon share in the catches was 79 %, and for stellate sturgeon, it was 21 %. There have also been recorded some differences of the Russian sturgeon and stellate sturgeon length composition between the early spring and middle autumn, which can result from the fact that the sturgeon individual of greater length leave their wintering sites in the Azov Sea open waters earlier and sooner enter the coastal waters in spring. Conclusions. This study makes it possible to improve the assessment of the stock status and distribution for the sturgeon fish species in the Azov Sea.