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The objective of this study was to determine the effects of the prebiotics Immunoster and Immunowall (two commercial prebiotics) on growth performance of juvenile beluga (Huso huso). Prior to the feeding trials, fish were fed the basal diet to apparent satiation four times per day for a 4-week acclimatization period. The basal diet contained 42% crude protein, 14.5% crude lipid, 10.06% ash and 6.1% moisture. Then, 450 beluga juveniles weighing 95.6 ± 9.4 g were randomly distributed into 15 fiberglass tanks (2 · 2 · 0.53 m) in three replicates and kept at a density of 30 fish per tank. Two levels (1 and 3%) of Immunoster and two levels (1 and 3%) of Immunowall were added to the basal diet in place of cellulose.

This study investigated the effect of dietary Zn levels on growth performance, feed utilization, and hematological parameters of juvenile Siberian sturgeon (Acipenser baerii, Brandt 1869). The five semipurified diets were formulated by adding 0, 5, 10, 20, and 40 mg Zn kg -1 diet in the form of zinc sulfate (ZnSO 4 ) to provide the actual dietary value of 14.7, 20.8, 27.3, 37.7, and 46.4 Zn kg -1 diet, respectively. The results showed that dietary Zn elevating level significantly improved the growth and feed utilization of the fish (p \ 0.05), but not the hepatosomatic index (p [ 0.05). Erythrocyte number, hemoglobin concentration, and hematocrit were increased with raising dietary Zn level (p \ 0.05), whereas a regular trend was not observed in blood indices, including MCV, MCH, and MCHC. A significant increase was also found in the leucocyte number followed by their differential counts, except for eosinophil percentage. The broken line regression model indicated optimal dietary Zn level for growth maximization of fish was estimated to be 29.15 mg Zn kg -1 diet. In spite of well correlation with dietary Zn level, no break point was observed to estimate the juvenile Siberian sturgeon requirement based on the erythrocyte numbers.

Artificial hybridization was performed between Rutilus frisii kutum and Abramis brama orientalis of the Caspian Sea. Synchronization of spawning of female broodstock of both species was induced by injection of carp pituitary extract. Reciprocal crossings between R. frisii kutum ♀×A. brama orientalis ♂ (RA) and A. brama orientalis ♀×R. frisii kutum ♂ (AR) produced viable hybrid larvae without any clear particular pre‐ or postzygotic isolation phenomena. RA and AR hybrid larvae were reared to fingerling stage with survival rates of 22.5 and 28% and average weight of 6.8 ± 0.17 g and 9.0 ± 0.79 g, respectively. A heterosis of 45% was calculated for weight at fingerling stage. RA and AR hybrid fingerlings were cultured in polyculture along with Chinese carps for 6–7 mo and reached an average weight of 190–195 g and 235–255 g, respectively. Karyotyping of these hybrids revealed a modal diploid number of 2n = 50 for both groups, which is similar to those of the parental species. Discriminant function analysis on 28 morphometric and meristic characteristics of two parental species as well as their hybrids could separate these groups at highly significant level (P < 0.001). These results indicated an overall intermediate inheritance of the studied characters.

This study conducted to evaluate the effect of dietary zinc (Zn) levels on feed utilization, tissue Zn composition and serum enzyme activities of juvenile Siberian sturgeon, Acipenser baerii. Five isoenergetic and isonitrogenous semi‐purified diets were formulated with increasing Zn sulphate (ZnSO4.5H2O) level to provide the actual Zn values of 14.7 (control), 20.8, 27.3, 37.7 and 46.4 mg/kg diet. Each diet was assigned to three groups of 20 experimental Siberian sturgeons with uniform size (initial weight of 26.52 ± 0.94 g) for a period of 8‐week feeding trial. Results showed that growth performance and muscle protein content were significantly increased with increasing dietary Zn level up to 27.3 mg/kg (p < .05), beyond which they remained significantly unchanged (p > .05). Muscle lipid content significantly declined with increasing dietary Zn level. While muscle and serum Zn contents were not significantly changed among treatments (p > .05), liver Zn content tended to rise with increasing dietary Zn supplementation. Alkaline phosphatase, superoxide dismutase and glutathione peroxidase activities were also raised with increasing dietary Zn level. The adequate amount of dietary Zn requirements for the Siberian sturgeon was estimated to be 28.24 mg/kg based on the relative growth rate and 34.60 mg/kg based on the liver Zn content.