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The oxidation of fat in fish diets due to oxygen penetration, high temperature and metal catalysts is common. The effects of feeding diets containing oxidized fish oil on the growth indices and lipid metabolism in young hybrid sturgeons (Huso huso ♂× Acipenser ruthenus♀) was investigated. Three different diets were implemented to three different groups: a control group, Group OFO_50 (50% oil fish oxidized) and Group OFO_100 (100% oil fish oxidized). 90 young sturgeon hybrids with an average initial weight of 212/6 ± 0/7 g, , were randomly divided into 9 fiberglass tanks with a volume of 700 liters after a 2 week adaptation period. Feeding was performed three times a day (8:00, 14:00 and 20:00) according to the specimens’ appetite during the period of the study. After 6 weeks, sampling was done to assay the growth parameters and biochemical indices. In both oxidized oil-fed groups, adverse impact on growth was seen. Also, a significant reduction in cholesterol and triglycerides was observed in the OFO_100 groups. The results showed that feeding hybrid sturgeons with diets containing oxidized fish oil, cause a negative impact on growth and lipid metabolism. Although a slight increase in the percentage of body weight gain and specific growth rate was recorded, it was undesirable and relevant to an increase in visceral fat.

The sub-lethal effects of water-born Cadmium (Cd) on histopathological changes of gill tissues were investigated on Sterlet, Acipenser ruthenus. In this research, 60 fish (41.69 ± 0.95 g and 23.98 ± 0.14 cm) were randomly distributed in 4 experimental groups, each with 3 replicates. The fish were exposed to different concentrations of Cd for 21 days under semistatic experimental condition as: 0, 16, 32 and 64 µg/L Cd. At the end of the experiment, the gill tissues were fixed in Bouin's solution for histopathological studies. Qualitative and quantitative changes of the gill tissues were analyzed. Several qualitative changes including hyperplasia, hypertrophy of epithelial cells and epithelial edema as well as necrosis, rings and fusion of gill filaments and secondary lamellae were observed in all treated fish including control group. Quantitative analysis based on organ index (Iorg) showed significant increase in histopathological changes in the gill tissues coincided by elevation of Cd concentration in the water. However, there was no significant differences in the organ index between control and 16Cd group.The results of this study demonstrate severe histopathological changes in the gill tissues after exposing to sub-lethal concentration of water-born Cd under experimental condition. The results of this study might be used as a guildline for evaluation of histopahological changes being induced by heavy metals in natural or cultivated environment for sturgeon fish.

This study was conducted to assay the effects of different levels of dietary vitamins C and E on growth indices in Acipenser ruthenus in International Sturgeon Research Institute. Nine diets were supplemented with a combination of 0, 100 and 400mg/kg food vitamin C and 0, 100 and 400mg/kg food vitamin E and were fed to sterlets in 2 replicates during 15 weeks. Two hundreds and seventy sterlets with the average weight of 350.92±14.28g were introduced to 18 tanks (each tank 15 fish). The fish were fed with 3% of body weight per day. The results showed that the highest and the lowest weight gain were in fish fed with diet containing 400mg/kg vitamin C and 0mg/kg vitamin E, respectively. The highest and the lowest Feed Conversion Ratio (FCR) were measured in control and diet 100mg/kg vitamin C and 400mg/kg vitamin E. A significant difference was found in FCR between treatments. The lowest and the highest amounts of Growth Rate (GR), Specific Growth Rate (SGR), Body Weight Index (BWI), Food Efficiency (FE) and Protein Efficiency Ratio (PER) were found in control and treatment 100mg/kg vitamin C and 400mg/kg vitamin E, respectively. This difference was significant between the treatments. In conclusion vitamins C and E have an important role in enhancement of growth performance and feed efficiency of sterlet.

Aquaculture for human consuming species is being considered as the first substitution of catching aquatic species due to increase of human population and decrease of wild aquatic stocks. In this study, the hybrid sturgeon Bester (female beluga x male sterlet) was produced for the first time in Iran. Sperm of 1.35 kg male Acipenser ruthenus was used to fertilize the eggs of 125 kg female Huso huso in Shahid Marjani Sturgeon propagation center (Agh Ghala, Golestan province). The fries of bester and control treatment of beluga were transported to International Sturgeon Research Institute (Rasht) after about one month by reaching to 490 mg and 377 mg of weight respectively. All fishes fed by artificial concentrated food (48-50% protein and 15-17% fat) after a period of feeding with Artemia and Daphnia. Sorting was carried out according to increase of fish weight for both fishes. Results showed that the imported sterlet spawners were not at the high maturation stages and especially the males had not suitable sperm quality. It showed that up to 2 months of age , these was no significant difference between bester and beluga weight but from this age up to 2 months of age the weight of beluga was greater. Meanwhile from 2 months old up to the end of the study (21 months) the weight of bester sample was significantly greater than beluga. The comparison of FCR for the whole rearing period showed no difference between bester and beluga (2.4 and 2.3 respectively). In general, the increase and decrease pattern of GR and SGR were coincided to each other, but showed monthly differences. Growth rate (GR) and specific growth rate (SGR) of bester were greater than beluga from 4th and 3rd month of rearing period respectively.