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Five hundred and ninety two Siberian sturgeon fingerlings (average weight, 11.1±0.9 g) were randomly distributed in 16 tanks (150 L) at a density of 35 fish per tank and fed different treatments (Control, degrading bacteria, 2% PHB, degrading bacteria + 2%PHB) for 60 days. At the end of the experiment, no significant difference was observed in case of final weight in fingerlings but fish fed PHB and degrading bacteria had lower FCR then the others (P<0.05). Also dietary treatments affected on the lipid percentage in fish muscle and lowest lipid content was observed in supplemented diets (P<0.05). The bacterial metabolic activity of fingerlings hindgut was investigated by biological oxygen demand (BOD₅) method using Oxitop® bottles and the results showed that the highest bacterial metabolic activity was seen in fish fed PHB. Also, at the end of the BOD test, bottles pH was measured and the results indicated that the lowest pH was observed in PHB and degrading bacteria treatments. The results in this experiment show that PHB and degrading bacteria have beneficial effects on growth performances and bacterial metabolic activity of Siberian sturgeon fingerlings. Such effects could be considered for new applications in aquaculture.

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The present study examined the effects of various concentrations (0.1-1.1 ml L^-1) of 2-phenoxyethanol, an anesthetic agent, on the stress responses, the hematological parameters and the hepatic enzymes in Siberian sturgeon (Acipenser baerii; Brandt JF, 1869).  The results showed that placing Siberian fish in low concentrations of the drug causes deep anesthesia over a longer period in compared with higher concentration, but the time required for fish recovery significantly decreases. Furthermore, plasma cortisol levels significantly increased (P< 0.05) and decreased (P< 0.05) at low (0.1- 0.5 ml L^-1) and high (0.9 and 1.1 mg L^-1) concentrations of 2-phenoxyethanol in compared to the control group, respectively. Different concentrations of 2-phenoxyethanol had no effect on the levels of WBC (P> 0.05), but the levels of RBC, hemoglobin and hematocrit significantly increased in the concentrations of 0.1 and 0.3 ml L^-1 of the drug (P <0.05). It was seen no changes in the ions levels of blood plasma as well as MCV, MCH and MCHC in compared with the control group in the different concentrations of 2-phenoxyethanol (P> 0.05). ALP and AST levels in high concentrations (0.9 and 1.1 ml L^-1) of anesthetic agents had not significantly different with the control group, but their values significantly increased at low concentrations of the drug (0.1 and 0.3 ml L^-1; P <0.05). In conclusion, these findings show that 2- phenoxyethanol at doses of 0.9 and 1.1ml L^-1 is suitable for the anesthetization of Siberian sturgeon because these concentrations have the least effects on the physiological system of fish.
 

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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.

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The aim of the present study was to investigate the effects of Nostoc algae on the growth indices of Siberian sturgeon (Acipenser baerii). A total of 72 juvenile Siberian sturgeon with an average weight of 140 ± 4 grams were allocated to four treatment groups, each with three replicates. The treatments included a control diet (without algae extract), treatment one with 0.5% extract, treatment two with 1% extract and treatment three with 2% extract of Nostoc algae. The fish were fed over a period of 42 days. Biometric measurements were taken both at the beginning and at the end of the experimental period to evaluate the growth indices. Data analysis at the end of the experiment revealed that specific growth rate (SGR) and weight gain (WG) were highest in the 2% algae treatment, while the control group had the lowest performance. The highest feed conversion ratio (FCR) was achieved in the control group, while the lowest FCR was observed in the 2% algae group. The best condition factor (CF) was recorded with the 0.5% algae treatment, while the lowest CF was associated with the 1% algae treatment (P < 0.05). Overall, these results indicate that the addition of Nostoc algae at different percentages significantly improved the growth indices of Siberian sturgeon. Based on the research results and the knowledge gained from the different treatments, the use of nostoc algae at a concentration of 2% seems to be the best option to improve the growth indices of Siberian sturgeon (Acipenser baerii). This treatment showed the highest growth and body weight gain compared to the other treatments. In addition, the treatment with 0.5% nostock algae seems to provide the highest condition factor (CF). However, in terms of weight gain and overall growth, the 2% treatment shows clear superiority.