Siberian sturgeon (Acipenser baerii) grows rapidly in breeding ponds. Gynogenesis is a suitable technique for producing sturgeon female sex. The aim of this study was to establish female sex in Siberian sturgeon using induction of gynogenesis. The sperm of Persian sturgeon (Acipenser persicus) was genetically inactivated by UV radiation at a dose of 8514 J/m2. In this case, sperm with 40% motility were combined with Siberian sturgeon oocytes and in 2°C cold shock for 30 minutes, 10 minutes after activity, gynogenic progeny were created. Fertilization rate was 44.5% (control hybrid 62%) and hatching rate was 19.8% (control hybrid 40.5%). Purely maternal heritability in gynogeneic progeny was confirmed using microsatellite markers. By achieving the biotechnique of sperm production with inactivated DNA of Persian sturgeon, it is possible to prevent the risk of extinction and protect other sturgeon by inducing gynogenesis.

Siberian sturgeon (Acipenser baerii) was introduced to Iranian aquacultural system as a proper and valuable candidate. Since rearing density is considered as an important stressor in aquaculture, this study was conducted to investigate the impacts of rearing densities on chronic stress using blood cortisol-glucoses levels and growth indices (Total length: TL and Body weight: BW). In total 90 specimens (TL: 45.3±1 cm and BW= 342±30 g) were stocked in three densities (24, 48 and 72 specimen/m3) during a five-month rearing period. There was no significant interaction between density-time parameters and cortisol-glucose levels (P> 0.05), whereas time solely displayed a significant correlation with cortisol-glucose levels (P<0.05). In contrast to the cortisol-glucose levels, the growth indices showed a significant interaction with density-time parameters (P<0.05). Our study suggests that Siberian sturgeon can tolerate stresses as result of high rearing density (72 specimen/m3), which are used for Iranian sturgeons.Keywords: Stress, Rearing density, Cortisol-glucoses levels, Siberian sturgeon1M.Sc. Graduate, Dept. of Fisheries, Tehran University, 2Assistant Prof., Dept. of Fisheries, Tehran University, 3Assistant Prof., Laboratory of Fish Diseases, International Sturgeon Research Institute, RashtReceived: 12/26/2011; Accepted: 05/06/2012Abstract Siberian sturgeon (Acipenser baerii) was introduced to Iranian aquacultural system as a proper and valuable candidate. Since rearing density is considered as an important stressor in aquaculture, this study was conducted to investigate the impacts of rearing densities on chronic stress using blood cortisol-glucoses levels and growth indices (Total length: TL and Body weight: BW). In total 90 specimens (TL: 45.3±1 cm and BW= 342±30 g) were stocked in three densities (24, 48 and 72 specimen/m3) during a five-month rearing period. There was no significant interaction between density-time parameters and cortisol-glucose levels (P> 0.05), whereas time solely displayed a significant correlation with cortisol-glucose levels (P<0.05). In contrast to the cortisol-glucose levels, the growth indices showed a significant interaction with density-time parameters (P<0.05). Our study suggests that Siberian sturgeon can tolerate stresses as result of high rearing density (72 specimen/m3), which are used for Iranian sturgeons.

The present study was conducted to compare the growth indices and blood factors of sterlet (Acipenser ruthenus), Siberian sturgeon (Acipenser baerii) and their hybrid (Acipenser ruthenus ♀ × Acipenser baerii ♂) to produce a fish with larger size, larger eggs and more tolerant to environmental conditions than the parents. The hybrid was produced by mixing of the oocytes of one sterlet female with the sperm of a Siberian sturgeon. For this study, 75 juvenile Siberian sturgeon with a mean weight of 32.38 ± 0.36 g, 75 sterlet with an average weight of 32.38 ± 0.41 g and 75 hybrid with an average weight of 32.37 ± 0.41 g each with 3 replicates were distributed in 9 concrete ponds with a volume of 800 liters and reared for 10 weeks. Thirty days after the start of rearing, the growth of juveniles hybrid was significantly higher than that of sterlet (P < 0.05). By continuing to feed the fish until the end of the 72-day study period, hybrid growth was still significantly higher than that of sterlet, but not significantly different from Siberian sturgeon (P > 0.05). The amount of feed intake, weight gain, specific growth rate, and percentage of body weight gain in hybrid were significantly higher than the sterlet (P < 0.05). These indices were lower in hybrid than the Siberian sturgeon but were not significantly different (P > 0.05). The feed conversion ratio of hybrid was significantly lower than that of sterlet (P < 0.05), while no significant difference was found with Siberian sturgeon (P > 0.05). Except for total protein and mean corpuscular hemoglobin, the other hematological indices showed no significant differences among the fish (P < 0.05). The mean corpuscular hemoglobin in hybrid was higher than compared with Siberian sturgeon and sterlet and (P < 0.05). The sterlet × Siberian hybrid showed similarity to the Siberian sturgeon in terms of growth indices, which indicates that it has the characteristics of Siberian sturgeon that has a better growth rate than the sterlet. In terms of blood parameters, the hybrid showed the characteristics of both parents.

This study was carried out to evaluate the effects of rearing density on total and differential leukocyte count and serum cortisol level in Siberian sturgeons (Acipenser baerii). Three years old Siberian sturgeons (460±90g) were reared at five densities (6, 9, 12, 15 and 18 fish per one third of 500-liter tank) for an 8 weeks period. To examine the total and differential leukocytes level changes, blood sample of one third tanks population were analyzed at the first and end of study with taking 3 blood smears of each sample. In high stocking densities (15 and 18 fishes) a significant decrease in total leukocyte count took place caused by a considerable drop in lymphocyte count but percentage of neutrophils increased significantly (P<0.05). No significantdifference was found in monocyte and eosinophil percentage among the experimental treatments. There were no statistically significant differences in serum cortisol concentrations in different treatments (P>0.05). In overall, the results showed that: 1) chronic stress caused due to crowding condition reduced the immune potential of Siberian sturgeons. 2) Changes in blood cellular composition were better stress indicator than plasma cortisol levels in Siberian sturgeon.

The Siberian sturgeon (Acipenser baerii) is an economically important species. Sturgeon stock assessment during fingerling production is considered to be one of the most difficult phases of hatchery rearing. The present study investigated the expression of growth hormone (GH) mRNA in unfertilized eggs, fertilized eggs, eyed eggs (2 day before hatching), non-viable eggs and newly-hatched Siberian sturgeon. Knowledge about the expression of GH during egg and embryo development can help determine the quality of the eggs. This can help predict larval viability and, to some extent, directly determine the growth and survival of young fish. Little is known about the effect of this hormone on egg quality in sturgeon. The present study analyzed relative GH mRNA expression using the 2-ΔΔCT method. Ribosomal protein L6 (RPL6) transcripts were used as the housekeeping gene for normalization of GH mRNA transcription. The highest levels of GH mRNA were found in eyed eggs and the lowest levels were detected in non-viable eggs (P< 0.05). These findings suggest GH mRNA as a potential marker for egg quality in Siberian sturgeon.

Determination of sex and gonadal development of Siberian sturgeon (Acipenser baerii) by using endoscopy as a new and less aggressive method for sturgeon conservation is the aim of this study. the gonadal development status of 23 Siberian sturgeons (7 years) by using endoscopy and histology for confirmation investigated in Shahid Dr. Beheshti Sturgeon Fish Propagation and Rearing Complex, located in Guilan, Iran. The system consists of a 7.5 mm, 30°, 22 cm long cytoscope sheath, fiber-optic light, halogen cold light source (150 W, #30801, Gima, Gessate, MI, Italy) and video camera installed on laptop. The results showed 52% female and 48% male identified by endoscopy which histology studies confirmed it, so the accuracy of sex identification was 100%. Our results suggest that endoscopy is an efficient technique for sex identification as well as the determination of gonadal development stages in Siberian sturgeon. Correct performing of this method in sex identification and gonadal development stages can help conserving of this valuable fish and economy of our country.

During the summer of 2022, an infection appeared in siberian sturgeon (Acipenser baerii) reared in raceway system of Fars province. 30 pieces of fish with clinical symptoms were collected from the ponds. Bacterial samples were cultured from kidney tissue of fish using brain heart infusion (BHI) agar according to standard method. Gram staining, biological and biochemical tests were performed on the bacteria isolated from the samples; In addition, polymerase chain reaction (PCR) was performed on SrDNA16 gene. Initial isolation of bacterial culture colonies and biological and biochemical tests on the isolated bacteria showed that the isolates corresponded to the genus Staphylococcus. The results of the PCR test on the SrDNA16 gene with specific primers with accession number MK348063 in the gene bank created a band of 1500 base pairs (bp). The results of the analysis showed that the sequences belonged to Staphylococcus epidermidis with 100.00% similarity. This is the first report of the isolation of Staphylococcus epidermidis species from Siberian sturgeon (Acipenser baerii) farmed in southwest Iran. It was concluded from this study that further studies are necessary to investigate the pathogenicity of these organisms and their effects on Siberian sturgeon and other strains of sturgeon.

Based on IUCN criteria, sterlet sturgeon (Acipenser ruthenus) has been shown as vulnerable species. Its male sex is inadequate or absent in the most of propagation and rehabilitation centers of Iran. The aim of this study is the induction of gynogenesis to produce male sterlet sturgeon using heterologous sperm. DNA of heterologous sperm from Siberian sturgeon (Acipenser baerii) was damaged successfully by UV irradiation with 473 µw/cm2 intensity and 90 seconds duration. The irradiated sperm mixed with sterlet sturgeon eggs to induce gynogenetic progenies of sterlet sturgeon. For this purpose, 15 minutes after activation, the fertilized eggs exposed to 34ºC heat shock for 2 minutes. Gynogenetic progenies were verified by microsatellite markers (AFU68 and AFUG195) as only maternal heritability. Histological observations of preliminary gonads of gynogenetic progenies were carried out by biopsy method at 17 months-age. Results showed that gynogenetic progenies consisted of 76.6% female and 23.3% male. Regarding to female heterogametic sex determination system in sterlet sturgeon, this study showed that both female and male as pure could be induced by inactivated heterologous sperm and gynogenesis.

This study aimed to determine the effects of replacement fish meal by different levels of gammarus meal on growth performance and body composition of juvenile Siberian sturgeon (Acipenser baerii). We distributed 245 Siberian sturgeon juveniles (initial body weight: 14.24±0.15 g) in five treatments and three replications. The experimental diets were replaced by 10%, 20%, 30%, and 40% gammarus meal. During the 9-week feeding period, the fish were fed with the experimental diets to apparent satiation four times daily. According to the results, there were no significant differences in the protein and fat efficiency ratios, visceral index and survival rate (P>0.05). The fish that received 10% and 20% treatments had a significantly greater mean final weight, weight gain, feed conversion ratio, body weight increase, final length, condition factor, specific growth rate, food intake and hepatosomatic index compared with the other treatments (P0.05). The results of this study indicated that a diet with 20% gammarus meal could be used in Siberian sturgeon feed.

The aim of this study was to evaluate the effects of lactobacillus plantarum probiotic in diet on some nutritional indices as well as survival rate in Siberian sturgeon (Acipenser baerii). This research were randomly designed in three treatment and one control groups in three replications with probiotic-contained diet, e.g. 107, 108 and 109 probiotic bacterial cells per gram food and the control group with no probiotic, which were treated for 60 days and then evaluated. 240 numbers of 37.666 ±1.094g of Siberian sturgeon were randomly distributed on 12 fiberglass ponds. Results showed that the used probiotic bacteria was able to strengthen the growth parameters (weight, FCR and PER) and significant increase in PER indicators and significant reduction in PER in treated with probiotics groups compared with the control group. In this study, the treatment with log8 L. plantarum indicated significant differences between all treatments and control. The survival rate in all treated and control groups were 100 percent. The results showed that the L. plantarum probiotic work as a growth promoter in Siberian sturgeon.