In the present study, the inlet and exit waters of two trout farms that were situated on the 4 th and the 20 th km of the Abant Rivulet in Bolu (Turkey) were investigated in a 10-month period between August 2011 and May 2012 in terms of their physicochemical parameters; the results were evaluated in terms of the environmental impact that they generated. Both of these farms, entitled as A and B in the present study, produce rainbow trout. Among the significant parameters that were determined in

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... he inlet and exit waters in farm A throughout the study period, the following values were obtained: temperature 12.7-12.4°C; pH 8.3-8.5, 8.1-8.5; conductivity 171.5-354, 170.8-353 µS/cm; turbidity 0.38-18.30, 0.13-19.15 NTU, COD 16.5-65, 32-72 mg/l; orthophosphate 1.47-19.75, 0.63-12.67 mg/l; nitrite 0.02-0.11,0.03-0.10 mg/l; nitrate 0.83-5.5, 0,1-5.85 mg/l; ammonium 0.02-1.04, 0.13-0.99 mg/L. The values that were recorded in farm B were as follows: temperature 12. 6-12.7°C; pH 7.8-8.4, 7,9-8.3; conductivity 190.3-336.7,122-335.3 µS/cm; turbidity 0.12-47.40, 0.10-47.35 NTU, COD 21.5-78, 24-75 mg/l; orthophosphate 3.73-54.67, 1.53-20 mg/l; nitrite 0.02-0.09,0.01-0.08 mg/l, nitrate 0.70-1.93, 0.60-9.50 mg/l, ammonium 0.09-0.88, 0.10-088 mg/l.