Acipenser Ruthenus Linnaeus Research Articles

Ефективність вирощування молоді осетрових (Acipenseridae) видів риб за різної твердості води

Ефективність вирощування молоді осетрових (Acipenseridae) видів риб за різної твердості води

Влияние иммобилизованной формы пробиотического препарата «Экофлор» на показатели неспецифического гуморального иммунитета осетровых рыб

Currently, due to the intensive development of aquaculture, interest in the study of the immune system and im-mune response in fish has increased. When growing fish in aquaculture, the conditions of their maintenance should contribute to maintaining the optimal activity of innate immunity. It has been established that the immunity of fish is more dependent on external influences, and environmental conditions are active regulators of fish immunoreactivity. Currently, various probiotic preparations with the ability to correct microbiological and immune parameters due to the action of symbiotic microorgasms have been widely used in aquaculture to increase and regulate the immune homeostasis of fish. Information is presented on the conduct of experimental studies to assess the effect of the probiotic drug “Ecoflor”, immobilized on enterosorbent, on the level of bactericidal activity of blood serum, the number of immunodeficient individuals, the content of nonspecific immune complexes in blood serum and immunocompetent organs, as well as on the level of C-reactive protein of sterlet yearlings (Acipenser ruthenus Linnaeus, 1758). It is noted that the use of a probiotic drug in an experi-mental dosage of 6 g/kg of compound feed has an effect on the indicators of nonspecific humoral immunity. Thus, sterlet grown on compound feeds with the specified rate of drug administration is characterized by an increased level of bactericidal activity of blood serum – 98% and the absence of immunodeficiency – 0%. In addition, this dosage helps to reduce the concentration of nonspecific immune complexes in the blood serum to 2.25 ± 1.65 and immunocompetent organs of sterlet yearlings: in the liver and spleen to 0.06 ± 0.02 and 0.30 ± 0.30, respectively. The results of the analysis of the level of C-reactive protein indicate that this drug does not cause inflammatory reactions in the body of fish.

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).

Low-temperature preservation of sterlet reproductive cells (Acipenser ruthenus Linnaeus, 1758) by the acoustic-mechanical influence method

To preserve reproductive cells of rare and endangered species of sturgeon fish using low-temperature cryopreservation methods, acoustic-mechanical impact with the use of piezoactuators was used. As a result of the research, the optimum parameters of signal frequency and time of impact on sturgeon cells were established, at which a high survival rate of sperm after defrosting was observed.Using mathematical modelling, the mechanism of acoustic-mechanical influence was studied, which consists in the wave and mechanical action created by the piezoactuator, which leads to acceleration of the process of diffusion of the cryoprotector inside the cells.For the first time a new methodological approach to low-temperature preservation of fish reproductive cells with the use of acoustic-mechanical impact has been proposed, which makes it possible to preserve genetic material with high survival rate and quality indicators.

Genetic Assessment of Remnant Sub-Populations of Sterlet (Acipenser ruthenus Linnaeus, 1758) in the Upper Danube

While the potamodromous sterlet was common in the past throughout the Upper Danube in Germany and Austria, it nearly vanished in the second half of the 20th century. Until recently, only one small and isolated reproductive sub-population is known from the German–Austrian border. However, isolated remnants in another section downstream of Vienna, near the Austrian–Slovakian border, were discovered in 2014. An assessment of the population size is one of the most important prerequisites for conservation management. This study aims to assess the population sizes at both sites, using genetic pedigrees and comparison to mark–recapture data. A total of 193 samples collected from these populations between 2011 and 2021 have been investigated. In addition, 59 samples from captive stocks, 38 wild fish from downstream, and 247 genetic profiles from previous studies were used for comparison. Results show close relationships and intermittent reproduction on one site. Estimated populations based upon genetic pedigree are very small, and are consistent with mark–recapture results. Small population sizes of remnant populations have only limited, sporadic reproduction, as well as continual losses to outmigration support conservation actions for sturgeons in the Upper Danube, including the restoration of functional migration corridors.

К оценке работ по реакклиматизации стерляди Acipenser ruthenus Linnaeus, 1758 в верховьях Днепра

Based on the results of ichthyological monitoring of VNIRO, a preliminary assessment of the work on the reaclimatization of sterlet in the upper reaches of the Dnieper River within the borders of the Smolensk region is given. Data on its occurrence in catches of smooth nets, size and age indicators, stages of maturity of gonads are given. A comparison of the nutrition composition of the Dnieper sterlet with the sterlet of the upper reaches of the Oka and Klyazma rivers is given. The dynamics of the output of juveniles, the average biomass of sterlet in the riverbed within the borders of the Smolensk region are shown. Accounting of early juvenile fish in the Dnieper for a number of years showed the absence of sterlet larvae in ichthyoplankton traps. To confirm the naturalization of this species of sturgeon, it is necessary to increase the number of ichthyological monitoring sites on the territory of the Republic of Belarus.

Процесс развития воспроизводительной системы у самцов осетровых рыб в индустриальных условиях на примере стерляди волжской популяции

The article describes special aspects of reproduction system development in male sturgeons using Volga sterlet population as an example (Acipenser ruthenus Linnaeus, 1758) within industrial enterprise of the Konakovskiy coarse fishery branch of the FSBSI Russian Federation Research Institute Of Fishery and Oceanography (VNIRO). The study results showed that gonad maturation stage I–II is completed at the age of 2 years if the total thermal constant is at least 11 thousand degree-days. Cytological sex differentiation occurs in the formed gland and begins at the age of three years if the thermal constant is more than 15 thousand degree-days. The onset of cytological differentiation can be determined by spermatogenesis waves characterised by intensive development of the male gonad III–VI maturity stages. Semelparity is typical for sturgeons, thus, the wave of spermatogenesis is seasonal, which indicates their limited participation in the spawning season at fish farms with natural water temperature. The knowledge of reproductive system development aspects in male sturgeons as illustrated by Volga sterlet population in the setting of industrial enterprise allows improving the practice of spermatogenesis process management at industrial farms ensuring the production of reproductive products of high fish-breeding quality at the time required for the enterprise. Considering the thermal constants made up by sterlet (males) spawners, it is possible to synchronise fish breeding processes (cycles) when receiving reproductive products from female sterlet and ensure repeated production of reproductive products from the same males in the settings of farms with controlled water temperature (throughout a calendar year). English version of the article is available at URL: https://panor.ru/articles/process-of-development-of-the-reproductive-system-in-male-sturgeon-in-industrial-conditions-on-the-example-of-the-sterlet-of-the-volga-population/68305.html

Formation of broodstocks and commercial productive stocks of sterlet (Acipenser ruthenus Linnaeus, 1758), beluga (Huso huso Linnaeus, 1758) and bester (Huso huso × Acipenser ruthenus) in Azerbaijan

The results of formation of broodstocks and commercial productive stocks of sterlet (Acipenser ruthenus Linnaeus, 1758), beluga (Huso huso Linnaeus, 1758) and bester (Huso huso × Acipenser ruthenus) on the Samukh commercial farm in Republic of Azerbaijan are presented. In 2019, for the first time in the history of fishbreeding in Azerbaijan, a progeny was received from grown “from eggs” sterlet females at age of 4 years at the Samukh fish farm using RAS. The mature eggs were stripped using minimally invasive microsurgery method by S.B. Podushka. After the egg collection sterlet females were transferred into holding basins for rehabilitation, further growing and second maturation. The total number of sterlet larvae from domestic broodstock exceeded 100 thousand. An ovulated beluga eggs were received from grown in aquaculture females at the age of 15 in December 2020. In result of fertilization of beluga eggs by sterlet sperm, hybrid (♀ Huso huso × ♂ Acipenser ruthenus) progeny was obtained and successfully grown on the farm. In future the domestic bester broodstock would be formed. The received data demonstrated that functional development of fingerlings and juveniles of sterlet “from eggs” sterlet farm took place without noticeable deviations from physiological normal physiological indices. The number of red blood cells per unit volume of blood increased in ontogenesis. On the contrary the number of white blood cells had seasonal variability and did not directly depend on the age of young sterlet.

ПОЛИМОРФИЗМ ДНК, ГЕНЕТИЧЕСКАЯ ОРИГИНАЛЬНОСТЬ И ИДЕНТИФИКАЦИЯ ПОПУЛЯЦИЙ И РЕМОНТНО-МАТОЧНЫХ СТАД СТЕРЛЯДИ (ACIPENSER RUTHENUS)

DNA polymorphism has been studied, indicators of genetic diversity and genetic originality have been de-termined for three natural populations and three replacement broodstocks of sterlet (Acipenser ruthenus Linnaeus, Acipenseridae) from the Volga Federal District. In the group of A. ruthenus replacement broodstock, 106 ISSR-PСR markers were identified, and in the group of natural populations, 103 ISSR-PСR markers. The indicators of genetic diversity and the coefficient of genetic originality (CGO) were slightly higher in the group of natural populations. Analysis of genetic structure of natural populations and groups of broodstock herds A. ruthenus showed that the coefficient of genetic differentiation are also slightly higher in the group of natural populations and equal 0,377. As a result of molecular genetic iden-tification, generic and species identification fragments of sterlet DNA were revealed, as well as combina-tions of polymorphic fragments for identification of the studied natural populations and stocks. The data obtained can be used to preserve the gene pool of populations, which is characteristic for a particular re-gion.

Estimation the influence of vitamin-mineral complex on reproductive characteristics of sterlet (Acipenser ruthenus L.)

The article provides data on the use of a complex preparation, which includes sodium selenite and tocopherol (vitamin E) in the form of injections for sterlet breeders (Acipenser ruthenus Linnaeus, 1758). Obtained data confirm the ability of E-selenium to regulate metabolic processes towards the formation of reproductive tissue by optimizing them. Positive dynamics is manifested during the gametogenesis, in particular, the number of individuals with reproductive cells at the IV stage of maturity is increased.

ИССЛЕДОВАНИЕ ВЗАИМОДЕЙСТВИЯ ВОДЫ С ПЕРВИЧНЫМИ ОБОЛОЧКАМИ ЯЙЦЕКЛЕТОК РЫБ КАК СИГНАЛА К ИХ ПЕРЕСТРОЙКЕ

The article outlines studying the interaction of water with the primary membranes of fish eggs as a signal for their restructuring, which is important for developing the cryopreservation techniques. The reproductive cells of sterlet (Acipenser ruthenus Linnaeus, 1758) obtained during the spawning campaign served as the object of research. Water as a main activator of the functions of fish reproductive cells contacting with primary membranes of eggs (two yellows and one surface jelly-like) triggers a mechanism that changes the structure and functional activity of eggs, stimulates the preparation of eggs for fertilization, provoking the rearrangement of organelles and changes in the membranes. The latter are activated contacting with water and, regardless of the fact of fertilization, acquire various properties (stickiness, buoyancy, increased strength) necessary for the further development of embryos, depending on the conditions of incubation. Changes in the properties of the membranes are stipulated by the presence of certain fatty acids, further chemical transformations of which are the main factor of their changes, according to the biology of reproduction.

Comparative characteristics of fishery indicators of various sturgeon species when grown in natural temperature regimes of water bodies of the Republic of Karelia

The paper presents materials on the rearing of Siberian sturgeon of the Lena population (Acipenser baerii Brandt), sterlet (Acipenser ruthenus Linnaeus) and their hybrid sturgeon (Acipenser baerii Brandt × Acipenser ruthenus Linnaeus) in the conditions of natural temperature regimes of natural reservoirs of the Republic of Karelia. It is noted that the climatic conditions of the region allow us to grow sturgeon to marketable sizes in cages in the natural temperature ranges of natural reservoirs. In order to determine the most suitable object for growing, the fish-breeding, biological and morphological indicators of Siberian sturgeon, sterlet and hybrid sturgeon were studied. The results of growing these objects in the cages of the Kedrosero fish hatchery showed their prospects for use in commercial fish farming. The highest indicators were observed when growing Siberian sturgeon, which showed a significantly higher rate of weight growth, good survival and effective use of feed. When grown for three years, the weight of Siberian sturgeon was 2053 g, sterlet — 682 g. The growth rate of the hybrid sturgeon was lower than that of the Siberian sturgeon and higher than that of the sterlet. The assessment of plasticity and exterior indices also showed the advantage of the Siberian sturgeon in comparison with other species. Fish-breeding, biological and morphometric indicators of sterlet and sturgeon hybrid were some lower, however, the high taste and nutritional value of these species make it possible to consider them quite promising objects of cultivation in the Northern regions.

ОПЫТ ИСКУССТВЕННОГО ВОСПРОИЗВОДСТВА СТЕРЛЯДИ (ACIPENSER RUTHENUS LINNAEUS) В УСЛОВИЯХ УСТАНОВКИ ЗАМКНУТОГО ВОДОСНАБЖЕНИЯ (МАНГИСТАУСКАЯ ОБЛАСТЬ)

The paper presents the results of artificial reproduction of sterlet (Acipenser ruthenus Linnaeus) carried out at the Scientific Production Center KazakhOsseter, LLP (the Mangistau region) in conditions of a recirculating aquatic system (RAS). The conditions for carrying out the main reproduction measures are described: wintering, qualifying, hormonal stimulation, obtaining reproductive products and rearing larvae. As a result, the sterlet spawning campaign was carried out in conditions of RAS in the Mangistau region, the native grown viable sterlet larvae being obtained. In the course of the work carried out in conditions of RAS in the Mangistau region there have been developed the scientific foundations and technologies for the formation and using production stocks of sturgeon, which are involved in the process of artificial reproduction. The results of the work performed could help to effectively organize the production at the commercial fish farming enterprises in the Mangistau region. The entrepreneurs of the region will have the opportunity to get acquainted with the technology of fish growing in conditions of RAS and to apply the technology for obtaining and reproducing sturgeon species in the ir local hatcheries in the future.

EVALUATION OF THE POSSIBILITY OF SEX IDENTIFICATION IN A STERLET BY MORPHOMETRIC INDICATORS OF THE STRUCTURE OF THE TAIL STEM

Representatives of the sturgeon family do not have pronounced external sex differences, which are typical of most aquaculture fishes. This causes some difficulties in their cultivation, the effectiveness of which largely depends on the timely division of the herd of fish into males and females, especially in caviar-commercial sturgeon farming. To date, none of the available methods for determining the sex of sturgeon is perfect. Some are traumatic, others are too expensive to use in commercial fisheries. This encourages the search for new methods and the development of effective ways to separate sturgeon by sex, which determines the relevance of research in this area. The aim of the study was to test the hypothesis of the presence of sex differences in the linear size of the tail stem in a member of the sturgeon family - sterlet (Acipenser ruthenus Linnaeus). The object of the study is the morphometric parameters of the tail stalk in the sterlet of adulthood. The subject of the study - differences in the structure of the tail of males and females of sterlet. Research methods - generally accepted in fisheries science ichthyological and statistical. The study was conducted in the training, research and production laboratory of fish farming of the Department of Aquaculture NULES of Ukraine in April and December 2019. The material for the study were the offspring of sterlet from a flock of fish kept in a closed recirculation aquaculture system of the fish farming laboratory. According to the results of the study, the hypothesis of a difference in the size of the tail stalk in male and female sterlet was not confirmed. However, according to the materials of pairwise correlation analysis of the dependence of the values of the indices of the structure of the tail stem on the age of the fish, a moderate inverse relationship was found between the relative thickness of the tail stem and the age of males and females of this fish. Females also showed an increase in the relative length of the tail stem with age. It was determined appropriate to continue similar studies on immature sterlet, aged 2 to 5 years.

Comparative Analysis of Benthophage Fish Nutrition in the Volga Reservoirs

Data on the nutrition of Acipenser ruthenus Linnaeus, Abramis brama (Linnaeus), and Blicca bjoerkna (Linnaeus) in the Volga reservoirs in 2001 and 2005 are given in the paper. The diet of A. ruthenus consisted mainly of Trichoptera and Mollusca, whereas that of B. bjoerkna included mainly Mollusca. In various reservoirs, the structure of A. brama food bolus significantly differed. In the Rybinsk Reservoir, A. brama food bolus included mainly Chironomidae, in the Gorky Reservoir - Polychaeta and Chironomidae, in the Kuybyshev Reservoir - Polychaeta and Crustacea, whereas in the Saratov and Volgograd reservoirs - Mollusca and Crustacea.

Reaction of osmoregulatory system of sterlet Acipenser ruthenus Linnaeus, 1758 (Acipenseridae) on influence of hyperosmotic medium

Some features of response to hyperosmotic environment (artificial sea water with a salinity of 12.5–12.7 ‰ (403–409 mosm/l) were studied in the osmoregulatory system of freshwater sturgeon species from the Volga river, starlet Acipenser ruthenus Linnaeus, 1758. Morphofunctional changes were traced in certain elements of the organ complex responsible for the osmoregulatory process. 72 hours after the immature sterlet individuals (age 2+) were transferred from fresh water to the hyperosmotic medium, blood serum osmolarity becomes iso-osmotic respective to the external environment. The interrenal gland responds to saline exposure by increasing cortisol concentration in the blood serum. A high cortisol level (75.13 ± 12.96 vs. 19.29 ± 6.36 ng/ml in the control group) persists throughout the entire experimental period (7 days), which indicates that fishes are under stress. The cortisol excretion into the bloodstream is not followed by an increased activity of the transport enzyme, Na+/K+ ATPase, in homogenate of the gills and an increased Na+ concentration in chloride cells, was identified by A-gold technique. The ultrastructure of chloride cells, being the main site for the removal and sorption of monovalent ions (Na+, K+, Cl-) in fishes, does not display the characteristic of an active excretion in sterlet. Thus, cortisol does not provide a stimulating effect on increasing Na+/K+ ATPase activity, an enzyme needed to transport excess ions from the body. The thyroid gland responds by increasing the thyroxin (T4) concentration during 3–6 hours of saline exposure. In the next 114 hours, the concentration of this hormone decreases to its initial level (in the control group). The thyroxin dynamics in serum does not correlate with the dynamics of serum osmolarity. So it seems possible to conclude that no functional relationship exists between the effector “organ” (the set of numerous chloride cells of the gills epithelium) and the endocrine glands (interrenal and thyroid) controlled by the hormones of tropic pituitary cells. In sterlet dwelling in hyperosmotic medium the kidney keeps a higher Na+/K+ ATPase activity, as compared with the gills. High Na+ concentration in the urine (163.2 ± 5.3 meq/l), close to its concentration in the hyperosmotic environment, high Na+ proportion (87.1 ± 0.1%) in the total concentration of major urinary cations, low level of water sorption (50.8 ± 4.0%) in the renal tubules, high diuresis (0.58 ± 0.09, ml/hr/100 g body weight) determine high level of Na+ excretion in the urine (100.95 ± 13.21 meq/ml/hr /100 g body weight). The important role of the kidney in removing Na+ excess under hyperosmotic environment underlies the osmoconformity strategy in sterlet.

Aннотированный список рыбообразных и рыб водоемов и водотоков бассейна верхнего Иртыша Восточного Казахстана с комментариями по их таксономии и зоогеографии

Приводится список рыбообразных и рыб, обитающих в водоемах и водотоках бассейна Верхнего Иртыша. Список содержит 43 вида, относящихся к 7 отрядам, 10 семействам и 30 родам. Включены все зарегистрированные на настоящий момент виды, валидность которых была пересмотрена в соответствующих систематических ревизиях. Три вида таймень Hucho taimen Pallas, 1773, нельма Stenodus leucichtys nelma Pallas, 1773, сибирский осетр Acipenser baerii Brandt, 1869 внесены в Красную Книгу Республики Казахстан. В бассейне Верхнего Иртыша к редким ценным видам, нуждающимся в сохранении генофонда из-за возможности его утраты, кроме уже внесенных в Красную Книгу Республики Казахстан можно отнести еще ряд видов: минога тихоокеанская Lethenteron camtschaticum Tilesius, 1811, стерлядь Acipenser ruthenus Linnaeus, 1758 маркакольский ленок Brachymystax savinovi Mitrofanov 1959.

Detection of white sturgeon iridovirus (WSIV) in sturgeons (Actinopterygii: Acipenseriformes: Acipenseridae) from aquaculture facilities located in Poland, Germany, and Italy

Background. White sturgeon iridovirus (WSIV) is one of the most serious threats for sturgeon aquaculture as the mortality in juvenile individuals can reach 95%. At the turn of the century WSIV was reported among hatchery-raised white sturgeon, Acipenser transmontanus Richardson, 1836,  in North America, Russian sturgeon , Acipenser gueldenstaedtii Brandt et Ratzeburg, 1833, in northern Europe but also pallid sturgeon, Scaphirhynchus albus (Forbes et Richardson, 1905) and shovelnose sturgeon, Scaphirhynchus platorynchus (Rafinesque, 1820) in North and South Dakota. The clinical signs of infection include cessation of feeding and edematous and pale gills. Those pathological changes lead to respiratory problems of the juveniles and deterioration of their overall condition. Rapid detection of pathogen particles under aquaculture conditions is crucial, therefore the principal aim of this study was to establish a molecular method for rapid and effective detection of the WSIV. This is the first study thoroughly comparing WSIV detection methods in sturgeons cultured in Poland, Germany, and Italy. Materials and methods. A total of 244 samples were collected from 82 sturgeons representing six species: beluga, Huso huso (Linnaeus, 1758); sterlet, Acipenser ruthenus Linnaeus, 1758; Siberian sturgeon, Acipenser baerii Brandt, 1869; Russian sturgeon, A. gueldenstaedtii; Atlantic sturgeon, Acipenser oxyrinchus Mitchill, 1815; and European sea sturgeon, Acipenser sturio Linnaeus, 1758, as well as five sturgeon hybrids: Siberian × Russian, Adriatic (Acipenser naccarii Bonaparte, 1836) × Siberian, Adriatic × beluga, Siberian × sterlet, and beluga × sterlet. The samples were screened for the WSIV using conventional PCR, real-time PCR, and in situ hybridization (ISH) methods. Results. In total, positive results were obtained in 231 (94.67%) out of 244 analysed samples, except for H. huso where DNA of WSIV was not identified. DNA of WSIV was most frequently detected in the kidney (97.92%), intestine (97.50%), skin (94.97%), and gills (93.29%). The most effective method for detecting DNA of WSIV in sturgeons was real-time PCR (92.62% of), PCR (90.98%), and ISH (49.24%). Conclusion. The host range of the WSIV seems to be wider than expected, however, further studies are necessary since no clinical symptoms were observed in sturgeons and their hybrids.

ВЛИЯНИЕ СКОРОСТИ ЗАМОРАЖИВАНИЯ НА РЫБОВОДНЫЕ КАЧЕСТВА СПЕРМЫ ОСЕТРОВЫХ РЫБ

The article describes the methods of cryopreservation which provides the reliable protection of cell organelles integrity after freezing-defrosting processes, as well as the needed supply of organic substances generating metabolic process in cells and tissues after a double temperature shock, and helps to achieve a significant progress in the cell long-term storage. There are considered the aspects of low temperature preservation of sturgeon sperm. Reproductive cells of Russian sturgeon ( Acipenser gueldenstaedtii Brandt & Ratzeburg, 1833) and sterlet ( Acipenser ruthenus Linnaeus, 1758) obtained at sturgeon hatcheries of the Astrakhan region and the research-expeditionary base “Kagalnik” in the Rostov region during spawning campaign served as the material for research. The purpose of the work was to establish optimal freezing rates during sturgeon sperm cryopreservation process that could ensure saving structural components of reproductive cells. It has been found that the freezing rate is species-specific. The best freezing speed for Russian sturgeon sperm proved to be 3°C/min. When experimenting with sterlet sperm there was registered less damage after freezing and defrosting at 10°C/min. Freezing speed 3°C/min was found less effective for sterlet sperm. Staged freezing process showed worse results in both cases. However, the quality of defrosted sperm didn’t get lower the fish breeding standards in all three studied speeds, which justifies sturgeon sperm freezing at all three rates subject to different conditions of preservation.

Population genetic structure and phylogeography of sterlet (Acipenser ruthenus, Acipenseridae) in the Ob and Yenisei river basins

The sterlet (Acipenser ruthenus Linnaeus, 1758) is a relatively small sturgeon widely distributed in Eurasian rivers from the Danube to the Yenisei. During the twentieth century, all wild sterlet populations have declined due to anthropogenic factors including: overfishing, poaching, construction of dams, and pollution. Despite the necessity of characterization both wild and captive stocks, few studies of population genetics have been performed thus far. Here we studied the genetic diversity and geographic structure of sterlet populations across the eastern range – Ob-Irtysh and Yenisei basins – by sequencing a 628-bp fragment of mitochondrial DNA control region. We identified 98 new haplotypes, delineated 12 haplogroups and estimated the time of basal haplogroup divergence within the species as over 8 million years ago. Our data suggest that Ob-Irtysh and Yenisei populations are isolated from each other and much lower genetic diversity is present in the Yenisei population than in the Ob-Irtysh population. Our data imply that sterlet populations in Siberian rivers underwent bottleneck or fragmentation, followed by subsequent population expansion. The data obtained here are important for sterlet population monitoring and restocking management.