Abstract In the present study, the impacts of phenol, a pollutant of inland water habitats, were investigated on Oncorhynchus mykiss. The fish (weight0300±7.5 g, total length018.58±3.8 cm) were subjected to 0.6, 1.2, and 2.4 mg/l of phenol concentration for 8 weeks. At the end of study, blood samples were taken via cardiac puncture by heparinized syringes, and hematological assays were done by standard methods. Red blood cell counts, hematocrit, hemoglobin concentration, and mean corpuscular hemoglobin concentration value decreased after phenol exposure while white blood cells counts showed an increase. The values of mean corpuscular hemoglobin and mean corpuscular volume were not affected by phenol treatment. Our findings showed that hematological parameters can be used as diagnostic indices to evaluate the health status of O. mykiss after exposure to phenol.
