A study on growth parameters, blood factors and proximate composition of rainbow trout (Oncorhynchus mykiss) cultured in underground brackish and freshwater

In this research, growth rate, blood parameters and proximate composition of rainbow trout (Oncorhynchus mykiss) cultured in brackish and freshwater were evaluated. Two treatments (brackish and freshwater) in 3 replications were investigated. Six 1.5 m³ fiberglass tanks were used for this experiment, containing 180 rainbow trout specimens with average weight of 47.2±0.1g. Feeding rate in treatments was about 3% of body weight based on water temperature and fish biomass. Total length and weight of fish were measured in 15 days intervals. After 135 days of culture period, some fish samples were transferred to the Lab. Blood were directly collected from the heart. Muscle composition was analyzed for proximate composition. The results showed that the body weight of samples in brackish water was increased significantly after 45 days of culture period. Blood factors including WBC, RBC, Hb, Hct, MCV, MCH, MCHC, lymphocyte, thrombocyte and concentration of K+ ions in fish cultured in brackish water showed a significant increase (P < 0.05). Muscle composition analysis showed a significant increasing (p < 0.05) in fat and dry matter in freshwater treatment, while moisture was significantly higher in brackish water (P < 0.01)