Growth performance of rainbow trout (Oncorhynchus mykiss) with respect to nutritional factors in north Iran (Haraz River)

Monthly samples of six fish farms from January 2010 to December 2010 in the northern Iran, Haraz River, were used to determine relationship between chemical parameters of main water, inlet and outlet and their effects on fish growth and production. Results revealed that concentration of nutrients in outlet was more than that of inlet of farms and statistical analysis showed that there were significant differences between stations (p < 0.05). The amount of phosphate in upstream farms was lower than that of downstream. There was statistically significant difference between nitrite nitrates, concentrations in different months. Total sulphide, phosphate and ammonium in inlets were 0.002±0.009 (mg/l), 0.215±0.113 (mg/l) and 0.022±0.018 (mg/l) respectively. In outlets there was 0.003±0.009 mg/l sulphide, 0.302±0.193 mg/l phosphate and 0.037±0.026 mg/l ammonium. Ammonium concentration, showed no significant difference (p>0.05) in different months Correlation between daily growth, SGR, FCR, production and chemical parameters of water were analyzed by Pearson Correlation. The results revealed negative correlation (α= 0.01) between nitrite and daily growth (P=0.004, Pearson Correlation=-0.24), ammonium and SGR (P=0.0001, Pearson Correlation=-0.272), although there were no correlation for FCR, and nutritional parameters (p>0.05).