2. Materials and methods
2.1. Fish
Four hundred and eighty Caspian white fish (R. frisii kutum) fry of average weight 1.12 ± 0.14 g were obtained from Shahid Rajaee Propagation and Rearing Center (Mazandaran province, Iran). Fish were acclimatized for 2 weeks in seawater aquaria (200 L) provided with Spongy filters (600 L h1 of flow) at Caspian Sea Ecology Research Center. The water was maintained at 21.2 ± 1.3 C, dis- solved oxygen at 6.7 ± 0.6 mg l1, pH 7.82 ± 0.4, electrical con- ductivity of 5736.4 ± 127.2 MM cm1 and salinity 10.3 ± 0.22 g l1.The photoperiod was of 14 h light and 10 h dark cycle. Fish were distributed randomly into 4 groups, each with 120 fish (40 fish per tank) before fed the experimental diets for 4 weeks. Fish were fed twice daily at 3% of body weight.