Rearing of Beluga (Huso huso) in Brackish Water of the Southern Costals of Caspian Sea

The present study was conducted with the objective to make use of low yielding coastal lands as well as the largest brackish water resource in the north of Iran. 600 Huso huso fingerlings with an average weight of 48.29 g were reared through a period of 18 months in a completely randomized statistical design. Brackish water transferred from the Caspian Sea was used in 4 tanks (Group 1) and freshwater from the Sepidrud River was used in the remaining 2 tanks (Group 2). Water flow in both groups was maintained at 0.2 to 0.5 L sec-1. During the first year of culture H. huso fingerlings were reared up to 314 g on diets containing 49 % crude protein and 9.7 % crude fat. During the second year fishes in Group 1 reached an average weight of 1983 g and those in Group 2 reached an average weight of 1911 g on diets containing 39.5 % crude protein and 12.8 % crude fat. The mean water temperatures during the first and second year of culture were 16.2 ± 5.9 and 17.4 ± 4.7 ؛C, respectively. Results of Anova obtained from biometric measurements during the first year indicate significant differences in FCR values obtained for the two groups at 95 % confidence level (F=32.6, P=0.0046). After 87 days of rearing FCR in Group 1 (1.19) was more suitable as compared to that in Group 2 (1.39). Anova conducted on FCR values obtained during a second year after 382 years of rearing conform with the results obtained for the first year and indicate significant differences in the two groups at a confidence level of 95 % (F=16.5, P=0.015). Results of Anova conducted on body weights of fishes during the second year after 517 days of rearing indicate significant differences between the 2 groups studied at confidence level of 95 % (F=9.54, P=0.036). Duncanandrsquos test conducted on results obtained also indicate significant differences between culture of H. huso in brackish water and freshwater. Statistical analysis of biometric measurements conducted during the first year of rearing indicate no significant difference in the final body weight of fishes in the two groups studied, however after 517 days of rearing significant differences were observed in the body weight of fishes in the second year. Body weight recorded for H. huso specimens are evident of better growth rates in fishes reared in brackish water fed diets containing 45 % protein and 12.8 % fat. During the first year of rearing significant differences were observed in FCR values obtained for the two groups studied that can be attributed to several factors including range in water temperature (16.2 ± 5.9 ؛C) that was lower than the required water temperature for optimum growth (18-22 ؛C) and shorter rearing periods (5 months). However in the second year better conditions in water temperature (17.4 ± 4.7 ؛C in Group 1 and 17.2 ± 5.1 ؛C in Group 2) and longer rearing periods (10 months) resulted in significant differences in body weights and FCR values in the two groups studied. These results not only conform with results of the first year but also reveal clear differences in growth rates observed in H. huso specimens reared in brackish water as compared to those reared in freshwater.