Acipenser Stellatus Research Articles

Cranial morphology of the Stellate Sturgeon, Acipenser stellatus Pallas 1771 (Acipenseriformes, Acipenseridae), with notes on the skulls of other sturgeons

AbstractExtant members of Acipenseridae are generally classified in four genera: Scaphirhynchus, Pseudoscaphirhynchus, Huso and “Acipenser,” which is widely recognized to be paraphyletic. Advances have been made in understanding the systematic relationships among sturgeons based on both morphological and molecular data. Analysis of mitochondrial DNA data suggested that Pseudoscaphirhynchus should be regarded as nested within “Acipenser,” specifically as sister group to the Stellate Sturgeon, A. stellatus. Recent morphological analyses also recovered this relationship, supported by a number of osteological synapomorphies, although these results were based on few and relatively small individuals. Here we describe the anatomy of the skull of A. stellatus based on newly prepared specimens of adult individuals, as well as examination of a large number of preserved individuals representing a broad range of ontogenetic stages. We present new anatomical data from all regions of the skull (dermatocranium, neurocranium, viscerocranium) and offer interpretations of these and other characters. In particular, we describe the allometry in the snout of A. stellatus, which undergoes substantial elongation relative to other sturgeons. Aspects of the skull of A. stellatus are compared to other members of the family, specifically the course of the occipital sensory canal and the morphology and distribution of cranial spines.

The aquaculture of Acipenseriformes. Part 6. Northern and South America

The history and contemporary state of global aquaculture of sturgeons and paddlefish are reviewed. The paddlefish Polyodon spathula became first object of cultivation of Acipenseriformes in USA. The paddlefish has high rate of growth in ponds using natural feeds, mature females can produce about 15% of their body weight in roe similar to eggs of star sturgeon Acipenser stellatus. Some liabilities include juveniles vulnerable to bird predation, poor tolerance to high densities, low oxygen and handling stress, waiting period of at least 7 years before females produce eggs. The paddlefish farming is carried out mainly in Kentucky, Indiana, Missouri and Alabama in polyculture with canal catfish Ictalurus punctatus or freshwater shrimp Macrobrachium rosenbergii. The most important object of North-American sturgeon breeding is white sturgeon Acipenser transmontanus, the biggest and fast-growing species of Acipenser genera. The largest commercial sturgeon farms are located in California, Idaho and Florida. A research program on biotechnology of white sturgeon farming has been initiated by the University of California at Davis in December 1979. The first successful artificial propagation of white sturgeon from Sacramento River was carried out in 1980, the first hatchery females matured in 1994. The hatchery progeny of Snake River white sturgeon was received in 1988, the first females matured in 2000. The first caviar was processed only after maturation of second generation. In Florida and North Carolina farmers used for cultivation small number of Russian sturgeon A. gueldenstaedti, Siberian sturgeon A. baeri, sterlet A. ruthenus, beluga Huso huso and star sturgeon A. stellatus. The total annual volume of sturgeon farming in USA was equal to 1285 tons (1166 MT). In Canada the only object of sturgeon farming is white sturgeon with annual production near 2 tons of caviar. In South America Uruguay has developed sturgeon culture with one large farm created in 1994 using help of Russian specialists.

The aquaculture of acipenseriformes. Part 5. Dunabe Basin and Middle East

The history and contemporary state of global aquaculture of sturgeons and paddlefish are reviewed. 5th part is devoted to sturgeon breeding in the basin of Black sea (without countries of former USSR reviewed earlier) аnd in the Middle East. Six species of sturgeon once migrated in the Danube River and Turkish rivers Yeşilırmak, Kızılirmak and Sakarya for spawning: anadromous beluga Huso huso, Russian sturgeon Acipenser gueldenstaedtii, stellate sturgeon A.stellatus, European sturgeon A. sturio and the river resident ship sturgeon A. nudiventris and sterlet A. ruthenus. Sturgeons had played an important role in the history Black sea fisheries, but due to overexploitation, followed by extensive river regulations and deterioration of water quality decrease in their populations has led most of them to the verge of extinction. During the 20th Century, world demand for sturgeon meat and caviar has inflated the economic value of sturgeons so Danube basin countries and Turkey develop commercial aquaculture and conservational programs. As result of protective measures the limited natural spawning of beluga, Russian and stellate sturgeons and sterlet is preserved in Danube. In Sakarya River last spawning population of stellate sturgeon exists. These species and Siberian sturgeon are important objects of commercial aquaculture in all countries of Black sea basin. The leaders of commercial sturgeon farming in this region are Bulgaria and Israel. The sturgeon aquaculture of Hungary and Turkey developed rapidly. Saudi Arabia and United Arab Emirates are important importers of caviar. Saudi Arabia is large consumer of caviar and UAE is one of main re-exporter of caviar. Both Arab countries develop own sturgeon aquaculture.

Genetic monitoring of progeny derived from natural spawning of Acipenser ruthenus Linnaeus, 1758 and Acipenser stellatus Pallas, 1771 as well as their hybrids in the Lower Volga river during the period 2017 to 2019

The state of natural spawning of sturgeons in the Lower Volga River was investigated through genetic monitoring of juveniles (larvae, fingerlings, subadults) captured at seven traditionally used monitoring locations. Sampling was performed during the period 2017–2019. In total, 460 individuals were caught and genotyped using a set of six microsatellite loci (Afug41, Afug51, Afug135, An20, AoxD161, AoxD165) and mtDNA control region sequencing. The observed species-specific microsatellite alleles revealed the presence of juvenile sturgeons originating from natural spawning also included some hybrids between Acipenser stellatus and A. ruthenus. Thus, the majority of sterlet breeding takes place in natural spawning grounds but also sterlet hybridizes with a small number of stellate sturgeons. Juveniles of other sturgeon species were not identified, and it is concluded that natural spawning activities of Russian sturgeon, beluga and ship sturgeon were insignificant or even absent in the Lower Volga during the observation period.

Cryoprotective activity of phosphorus-containing phenol

The antioxidant and cryoprotective efficiencies of a 3,5-di-tert-butyl-4-hydroxyphenyl)methylenediphosphonic acid (MDPA) differ significantly for sperm cells of various species of sturgeon fish (Russian sturgeon, beluga and Stellate sturgeon). The ability of phosphorus-containing phenol MDPA to decrease the level of lipid peroxidation of sperm, beneficial effect on the activity indicators of the sperm of native sturgeon and of the defrosted one after deep freezing as well as on the fertility of sperm cells was shown.

History and status of sturgeon stock (Acipenseridae) in the Caspian pool

Analysis of materials from long-term studies characterizing the current state of sturgeon stocks in the Volga-Caspian fisheries basin, and the dynamics of commercial catches of beluga, sturgeon and stellate sturgeon in the XX - XXI centuries indicates that the Northern Caspian occupies the leading value in catch volumes, where more than 70 % of sturgeon fish are annually harvested. In the first half of the twentieth century sturgeon stocks were determined by the scale of natural reproduction in rivers and fishing volumes; in the second half, natural and anthropogenic factors began to intensively influence the formation of sturgeon stocks. The development of hydraulic construction on rivers, an increase in the withdrawal of freshwater runoff, a decrease in sea level to -29.0 mBS, pollution by industrial and agricultural runoff have necessitated the development of a set of measures for the reproduction, conservation and rational use of the Caspian’s aquatic biological resources. As a result of the studies, the response of the sturgeons to the changed conditions of reproduction has been determined in order to restore and increase their commercial stocks; high ecological adaptability of sturgeons to various living conditions within their range, their exceptional plasticity and pronounced intraspecific differentiation have been established. These indicators point to the possibility of creating conditions that meet the requirements for water quality for the life of sturgeons during migration and reproduction. In the course of the analysis of the obtained data, the influence of regulation of the Volga River flow on the efficiency of natural reproduction of sturgeons has been evaluated; the role of industrial sturgeon breeding in sturgeon stock formation has been shown; the abundance of juveniles in the North Caspian and adult individuals on feeding pastures of the sea has been estimated; trends in the number of sturgeon producers migrating in the Volga to spawning sites have been identified; the prospects for the restoration and rational use of sturgeons in the Volga-Caspian basin have been determined.

Complete mitochondrial genome sequence and phylogenetic position of the Amu Darya sturgeon,Pseudoscaphirhynchus kaufmanni(Acipenseriformes: Acipenseridae)

In this study, we successfully assembled the complete mitochondrial genome of the Amu Darya sturgeon Pseudoscaphirhynchus kaufmanni. Based on this mitochondrial genome and previously published mitochondrial genomes of members of the Acipenseridae family, we assessed the phylogenetic position of P. kaufmanni using maximum likelihood and Bayesian inference for phylogeny reconstruction. The resultant phylogenetic trees were well-resolved, with congruence between different phylogenetic methods. This robust phylogenetic analysis elucidated the relationship among the four acipenserid genera and strongly supported the division of the family into three main clades. Evaluation of molecular phylogeny using maximum likelihood and Bayesian analysis led to the following conclusions: (a) the most basal position within the Acipenseridae remains in the clade containing Acipenser oxyrinchus and Acipenser sturio; (b) the genus Scaphirhynchus belongs to the Atlantic clade and is a sister group of the remaining species of the clade; and (c) the close relationship between P. kaufmanni and Acipenser stellatus is well supported.

ЭФФЕКТЫ СОДЕРЖАНИЯ ПРОИЗВОДИТЕЛЕЙ И МОЛОДИ РЫБ В РАСТВОРАХ ПОВАРЕННОЙ СОЛИ РАЗЛИЧНОЙ КОНЦЕНТРАЦИИ

The aim of the research is to develop new efficient method of fish cultivation in a medium with totally controlled conditions. The main task is the morpho-physiological and piscicultural-biological analysis effects of farming fish- breeders and juvenils in salt solutions of different concentrations. Laboratory and industrial fish contents tests for sea water and salt solutions medium of different salinity have been implemented on the most valuable fish species: russian and stellate sturgeon, rainbow trout, bullhead and roach.The results were evaluated by piscicultural-biological and physiological indicators: content state of hemoglobin, total protein, serum osmolarity, abdominal fluid and urine. Cytomorphometrical analysis of the hypothalamic-hypophysial neurosecreto-ry system (HHNS) status was performed by light and electron microscopy. The enhance effects of fish survival, breeders reproductive quality, youngs growth rates were first established for medi-um with "critical" salinity 4-8‰ For breed-ers originally it was shown the possibility to change sea water on the table salt solution of the same concentration. With such a low concentration of salt a new biostimulating effect of this artificial medium on the fish body was installed, due to the absence of its well-known toxicity. The highest degree of survival and delayed sex maturation of roach and stellate sturgeon were specifically in-stalled for the same concentration of indus-trial salt solutions. The best physiological body state was also shown in this solution (5‰) by physiological and biochemical analysis, regarding minimal losses in hemo-globin and serum protein. Histophysiological analysis of the sevruga HHNS state showed the smallest degree of activity in this solu-tion to the end of the experience, proportion-ate to the severity of stress. Such moderately active HHNS in solution of salt 5‰ clearly indicates the status of the eustress and high HHNS activity for control groups indicates the typical status of the stress. By electron microscopy study HHNS state sevruga and sturgeon in hypertonic salt solutions of dif-ferent concentrations it was shown, that at 17 and 22‰ they were under stress and at 32‰ represented irreversible disstress. All 3 in-stalled stress status depends on the intensity and duration of exposure. Their effects are alternative and therefore are managed, trans-forming from bio-stimulation in reversable stress and, after reaching the limits of physi-ological species cause toxic effect and then a state of disstress and death. The possibility of changing the sea water to industrial salt solution 5-7‰, allowed to develop "A meth-od to reserve fish breeders", which ,however, can not be applied for the young fish breed-ing. So the next stage in the development of this method was to test it already on juvenile and young fish, in order to determine its effective cultivation in this artificial biostim-ulating medium. The results of the search experience on trout fingerlings showed the increased survival and growth in salt solu-tions, especially in 12‰ as compared to con-trol. The first experimental verification of this method on the clarias bullhead finger-lings in the recycling aquacultural system (RAS) showed the largest growth rates in 5‰ salt solution, and its total survival in all variants. Received data and analysis of biostimu-lated effects impact on the body's critical salinity gives the opportunity to develop a fundamentally new way of cultivation of valuable fish species in an artificial biostim-ulated habitat. This technique can allow to manage breeding - obtaining offspring and the cultivation of young fish. It is aimed at improving the efficiency of breeding fish in aquaculture due to the availability of the application for any type of fish farms with the effects of increasing survival rate and young growth rate. It is expected that the change of the sea water with the cheap solu-tion of table salt can be widely practiced at fish plants in various fields and at all stages of fish biotechnology works, especially RAS.

Nanoemulsion production techniques upgrade bioactivity potential of nanoemulsified essential oils on Acipenser stellatus filet preserving

ABSTRACT The aim of this study was to prepare physically stable nanoemulsions containing three different essential oils (Rosemary, Cuminum, and Zataria Multiflora Boiss) by using two different nanoemulsification methods. Then microbial growth rate, antioxidant, and oxidant content of fresh fish fillet were assessed at 4°C and 10°C temperatures. Essential oils (EOs) were purified from Rosmarinus officinalis L., Zataria multiflora Boiss, and Cuminum cyminum L. and emulsified by two different methods: Ultrasonic Homogenization (USH) and Emulsion Phase Inversion (EPI). Samples of Acipenser stellatus (weight of 10 ± 1 g) were immersed in Nanoemulsified essential oils. Then antibacterial and antioxidant potential of these essential oils was analyzed by culturing in a tube and measuring PV and TBA, respectively, during 1, 3, 7, and 14 days after treatment. Cuminum cyminum L., at 4°C in the USH method reduced the growth of bacteria in the fish sample on all studied bacteria at 5% concentration compared to 3%. Also the results of Cuminum cyminum L. EO made by both methods used to emulsify the oil were better than the other two extracts. As well these results were observed for PV and TBA contents. This study showed that nanoemulsified Cuminum cyminum L. prepared by the USH method has good antioxidant potential and antibacterial effect among other essential oils and it can be used to produce novel natural antioxidants as well as flavoring agents that can be applied in different food products.

Monitoring of adaptive potential by functional loads and feeding regime of sturgeon juveniles

The article presents the results of research on the physiological and biochemical state of sturgeon juveniles using various functional loads at the early stages of post-embryonic development of sturgeon raised on an experimental diet in the presence of live food. The article analyzes the effectiveness of the application of functional load methods and feeding regimen to establish the physiological status of released juveniles to replenish natural populations. The article provides information about the stability of young sturgeon fish during the period of release from sturgeon hatcheries to replenish the natural population, further entry from fresh to sea water, and placement in places of natural feeding. The temperature and salinity of water for hydrobionts is a factor that has an integral effect on the activity of functionally important systems of the body at all stages of the life cycle. Juveniles obtained from artificial generations and grown in a combined way on various feeds retain high plasticity, adequate nutrition forms an osmoregulatory function and resistance to temperature conditions of the environment. It is proved experimentally that the feeding regime is an important factor affecting the fish-breeding and biological and physiological and biochemical parameters of young Russian sturgeon, stellate sturgeon and bester.

Contribution of the researchers of the Department of Ichthyology and Hydrobiology of Saint-Petersburg State University to the conservation of the Caspian sturgeon population

The paper deals with the main historical moments of the Caspian sturgeon population dynamics and the formation of their stocks. The participation of researchers of the Department of Ichthyology and Hydrobiology of Saint-Petersburg State University in creating the concept of sturgeon conservation in the Caspian Sea and the specialized institute of sturgeon farming in Astrakhan was highly appreciated. The materials on the contribution of the Department’s researchers to the study of the physiological state of sturgeon producers, improving their quality, survival and safety in the conditions of artificial breeding of these species are presented. The data on the reduction of the sturgeon abundance reared and released into the Caspian Sea by the Caspian littoral states are presented. A description of the current state of the sturgeon of the Caspian basin is given. The data on changes in stocks, the structure of the spawning part of the population and reproduction of the beluga, Russian sturgeon and stellate sturgeon in the Volga-Caspian basin under the conditions of the prohibition of their commercial fishing are analyzed. It was shown that during the years of the ban, the abundance and stocks of sturgeon and biological indicators of breeding migrants to spawn in the Volga continued to decrease and the proportion of females among them, which is associated with the illegal catch of sturgeon, comparable in scale to the commercial fishery before the ban was introduced. Reduced natural (up to its complete cessation in the Beluga) and artificial reproduction of sturgeons are stated. Only observing the moratorium on sturgeon fishing in all the Caspian littoral states, strengthening the protection of fish at feeding grounds and spawning migrations can preserve and restore their unique Caspian populations.

Review of data on the role of cortisol at the final stages of spawning migration and the reproductive cycle in sturgeons (Acipenseridae)

This review presents data on the role of cortisol (F) at the final stages of the reproductive cycle in migratory sturgeons (Acipenseridae) of the Volga-Caspian region: Russian sturgeon (Acipenser gueldenstaedtii Brandt et Ratzeburg, 1833), stellate sturgeon (Acipenser stellatus Pallas, 1771) and beluga (Huso huso (Linnaeus, 1758) obtained using a special variant of enzyme-linked immunosorbent assay (ELISA), which allowed us to compare the indicators of different years. The dynamics of F level in blood serum (BS) and the state of the interrenal gland (IG) in sturgeons were studied during feeding in the sea and at the beginning of the anadromous migration, as well as at the reproduction in the conditions of hatcheries. Higher levels of F in BS and high functional activity of IG are characteristic of sturgeon migrants when entering the river compared with data for fish during feeding in the sea. Reservation of sturgeon breeders at the hatchery led to decrease of the F serum level; and hormonal stimulation of maturation caused an increase in this indicator. Data on the F content in oocytes and abdominal (coelomic) fluid during maturation of female sturgeon are also presented. The F “profiles” were evaluated in sturgeon breeders under stress impacts that are unavoidable at the conditions of hatchery enterprises, as well as under experimentally simulated stress impacts. Peculiarities of the interaction of the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-interrenal axes in sturgeons during reservation at hatcheries and during hormonal stimulation of fish maturation are discussed. Particular attention is paid to the compilation of data contained in the works performed in the late 90s – early 2000s under the guidance of Dr. Sc., prof. I.A. Barannikova (1926–2017), to whose memory the review is dedicated.

Экологическая валентность к кислороду северокаспийских мизид и кумовых ракообразных

The paper focuses on the problems of violation of the ecological balance, changes in the nutrient load, undermining the ecosystem’s biopotential, caused by anthropological pressure and resulting in deterioration of the oxygen regime in the bottom layer of water. The purpose of the research was to determine the environmental oxygen tolerance in bottom invertebrates, representatives of the orders Mysidacea and Cumacea, which are forage objects for beluga, sturgeon, stellate sturgeon, bream and pike perch. The research was conducted in 2013-2017 in the western part of the North Caspian. Developing of oxygen deficiency in the studied water area was due to thermohaline stratification of water masses. Hypoxia was formed in local areas. Representatives of Mysidacea predominantly inhabiting the bottom layers have a low frequency of occurrence, because they live in a narrow range of oxygen content (about 5-7 mg/l). A low oxygen concentration (less than 3.95 ml/l (74%)) inhibits the development of Mysidacea. Paramysis ullskyi prevailed in the total number of samples taken from macrozoobenthos, and Paramysis lacustris prevailed in the total biomass. Limnomysis benedeni and Paramysis ullskyi were the most resistant to oxygen deficiency. These species have a maximum ecological valence to oxygen. Representatives of the order Cumacea are characterized by a high frequency of occurrence. The species Schizorhynchus bilamellatus dominated in the surveyed water area, both in abundance and biomass. Cumacea live in a wide variability of oxygen content. Schizorhynchus bilamellatus and Stenocuma graciloides are most resistant to oxygen deficiency. These species have a maximum ecological valence to oxygen. The minimum oxygen recorded over the entire research period (1.29 ml/l; 21%) is not critical for Stenocuma graciloides. The results of the study are of practical value for assessing the condition of the food supply of benthos-eating fish that are commercialized in the western part of the North Caspian

Food worthy of kings and saints: fish consumption in the medieval monastery Studenica (Serbia)

The paper focuses on fish consumption and long-distance fish trade in the medieval monastery Studenica in Serbia, from the perspective of archaeozoology and historical evidence. Medieval written sources on the subject suggest that fish was available primarily to particular social classes – the royalty, nobles and monasteries. Preserved muniments indicate that during the 13th-15th centuries the majority of distinguished monasteries had their own fishing ponds, fishing grounds and their own fishermen. Fish consumption occupied an important role in monastic contexts, both in Christian religious practices (e.g. Lent) and in celebrations commemorating the Virgin Mary and the monastery founder, during which high-quality fish was obtained from greater distances. The ichthyoarchaeological remains discussed in this paper originate from waste deposition areas within and outside of the ramparts of the Studenica Monastery, accumulated during the 14th and the first half of the 15th century. Apart from the remains of the species available more or less locally (Wels catfish [Silurus glanis Linnaeus, 1758], carp [Cyprinus carpio Linnaeus, 1758], pike [Esox lucius Linnaeus, 1758]), the faunal assemblage contained the remains of migratory sturgeons (beluga [Huso huso Linnaeus, 1758], Russian sturgeon [Acipenser gueldenstaedtii Brandt & Ratzeburg, 1833], stellate sturgeon [Acipenser stellatus Pallas, 1771]) most likely transported from the Danube area, about 200 km away as the crow flies. Skeletal element distribution, butchering traces and size estimations (of beluga in particular) indicate that large specimens (c. 2-3.6 m in total length) were brought whole to the monastery, possibly dried or salted. Their occurrence is an additional indicator of long-distance fish trade recorded in muniments, and it offers new insights into economic, social and religious practices in medieval Eastern Orthodox monasteries.

Ontogeny of digestive tract of Stellate sturgeon (Acipenser stellatus) from hatching to juvenile stage: Digestive enzymes activity, stomach and proximal intestine

This study was an attempt to evaluate ontogenic development of digestive enzymes activity, histomorphological changes of stomach and proximal intestine of Stellate sturgeon (Acipenser stellatus) from hatching up to 50 days post hatching (dph). The digestive enzymes activity of pepsin, trypsin, chymotrypsin, alkaline phosphatase, amylase and lipase was considered. Pepsin activity was detected in one-day-old prelarvae followed by a sharp increase at the beginning of larval stage (i.e., 8 dph) onward. However, few fluctuations coincided with changes of food types consumed by the fish. The highest chymotrypsin activity was observed at 1 dph. During larvae period, the enzyme activity showed two surges that occurred at 15 and 31 dph. Although descending trends for trypsin (with the highest activity at 8 dph) and amylase (with the highest activity at 24 dph) were observed, lipase and alkaline phosphatase revealed an incremental trend during early growth stages. At 10 dph, functional stomach was observed with epithelia containing some crypts. Intestinal morphometric indices such as intestinal folds were measurable at 4 dph; epithelium, however, appeared immediately after hatching. Pearson's correlation coefficient revealed positively related activities of trypsin, chymotrypsin and amylase. They all reflected negative relationships with pepsin, alkaline phosphatase and lipase. The findings suggest that gastric digestion of proteins become dominant during the ontogenetic development of Stellate digestive tract. Over this period, the fish relied on energy dense lipid molecules to meet their metabolic demands while they spare protein for further tissue synthesis/maintenance. Moreover, pepsin seems to be more responsive to the type of food consumed by the Stellate and might be a useful indicative of the nutritional status of the fish. The concluding remarks are discussed in light of the significance of various histological changes and their interrelations with ontogeny of digestive enzymes activity.

Long-Term Dynamics of Sturgeon Distribution in the Northern Part of the Caspian Sea (Review)

In the past 50 years, habitat conditions and distribution of sturgeons in the Caspian Sea have significantly changed. The longest term records of sturgeon distribution are obtained for the northern part of the sea, which is extremely important for the feeding of these species. In the present review, we summarize and analyze changes in the distribution of the beluga Huso huso L., 1758; Russian sturgeon Acipenser gueldenstaedtii Brandt, 1833; and stellate sturgeon Acipenser stellatus Pallas, 1771 in the northern part of the sea from 1970 until 2014 and the biotic and abiotic factors of these changes. The effect of the sea-level fluctuations, the biomass of food organisms, and the total abundance of the studied fish species on their distribution is demonstrated.

Detailed analysis of beluga sturgeon (Huso huso) and stellate sturgeon(Acipenser stellatus) migration in the Lower Danube River

The swimming ground speed and swimming depths of beluga sturgeon (Huso huso) and stellate sturgeon (Acipenser stellatus) were investigated using ultrasonic telemetry between 2011 and 2017 in the Lower Danube River (river kilometer (rkm) 0 Sulina-rkm 1075 Bazias). Acoustic telemetry receivers VR2W and V16TP tags (Vemco, Canada) were used to collect data about sturgeon migration behavior in the Lower Danube River between the Black Sea and the Iron Gate II dam. The tags, equipped with depth and temperature sensors, provided data about beluga and stellate sturgeon migration periods, swimming speeds, and depths. Twenty-three beluga sturgeon (184-245 cm TL) and twenty-one stellate sturgeon (92-135 cm TL) were ultrasonically tagged and passively tracked using hydrophone receivers installed in the river between rkm 71 and rkm 860. Three tagged beluga sturgeon returned after 2 and 5 years and two stellate sturgeon returned after 2 years since the time of their initial release in the river. This study provides, for the first time, further details concerning beluga sturgeon and stellate sturgeon migratory behavior patterns, traveled distances, swimming depths, and their swimming ground speeds during spawning migration.

Genetic diversity analysis of aquaculture strains of Acipenser stellatus (Pallas, 1771) using DNA markers

Acipenser stellatus (stellate sturgeon) represents a sturgeon species of great importance for the scientific community and fishermen that has been intensively captured for decades. Besides of overfishing and poaching, their reproduction sites have been destroyed and their natural habitats were affected by pollution. In consequence, wild populations of stellate sturgeon have decreased dramatically, this species being considered critically endangered. In order to conserve this species, efforts have been made to artificially reproduce native sturgeons and restock natural habitats with the broodstock. The genetic diversity analysis of the future breeders is of great importance in order to avoid the inbreeding depression and genetic drift. Six aquaculture strains of A. stellatus reared in fish farms from South of Romania were genetically analyzed. The assessment of the genetic diversity was made by using DNA markers, such as cytochrome b mitochondrial gene and microsatellite nuclear loci. The results showed a moderate genetic variability within the strains and a moderate genetic diversity between the strains. One strain was slightly inbred and is recommended not to be included in the reproduction programs. In conclusion, five out of six aquaculture strains were genetically distinct and can be used in selective breeding programs aimed to conserve stellate sturgeon from the Lower Danube River.

Novel X-ray sequences and crystal structures of Persian and Starry sturgeon methemoglobins: Highlighting the role of heme pocket waters in causing autoxidation

Although there is a high sequence similarity between mammalian and fish hemoglobin (Hb), the oxidation and heme loss rates can vary greatly between them such that fish Hbs oxidise much more rapidly than mammalian Hbs. There is to date no sequence or structural data for any sturgeon Hb to reveal the level of autoxidation in these fish. In this study, novel high resolution X-ray sequences and crystal structures of methemoglobin (Met-Hb) from two sturgeon fish including Persian sturgeon (Acipenser percisus) and Starry sturgeon (Acipenser stellatus) belonging to the Caspian sea has been determined. A comprehensive sequence and structure comparison between these sturgeon Met-Hbs and a number of non-sturgeon and normal and sickle cell anaemia human Hb in varying heme states has been carried out highlighting (i) the structural variability in the heme propionate groups; (ii) the existence of certain residues or their displacement and shift in the heme pocket allowing entry of water molecules into the heme pocket; (iii) the importance of the number of water molecules in the heme pocket; (iv) the hydrogen bonding between oxygens of A and D propionate groups and that of waters in the heme pocket; and (v) the role of heme binding waters causing oxidative stress and heme autoxidation.

Effects of starvation and refeeding on growth performance and stress defense mechanisms of stellate sturgeon Acipenser stellatus juveniles from aquaculture.

Acipenser stellatus represents a species of great economical interest due to its roe used for caviar production. Therefore, it has been intensively captured for decades and nowadays, this species is on the verge of extinction. As a consequence, Acipenser stellatus is intensively raised in fish farms. Aquaculture is focused on optimizing the feeding regime of juveniles. The aim of this study was to investigate if Acipenser stellatus can adapt to a starvation/refeeding regime by assessing the effects of this regime on growth performance, oxidative stress biomarkers and heat shock protein (hsp) gene expression in juveniles raised under aquaculture conditions. The juveniles were subjected to two starvation/refeeding regimes: a 7-day starvation period followed by 21 days of refeeding, and a14-day starvation period followed by 21 days of refeeding. The results had shown that the juveniles subjected to 7/21-day starvation/refeeding regime presented a complete compensatory growth, they were able to counteract the oxidative stress by enhancing activities of the antioxidant enzymes and they presented no significant changes in hsp gene expression. In contrast, 14/21-day starvation/refeeding regime negatively influenced growth performance, it induced a high level of oxidative stress that was impossible to counteract and it determined major changes in the hsp gene expression level in the liver of Acipenser stellatus. Thus, Acipenser stellatus seems to be able to adapt only to the 7/21-day starvation/refeeding regime that does not threaten the growth performance and the welfare of juveniles. Therefore, it could be useful to optimize the feeding practice in aquaculture production.