Abstract In this study, the blood parameters of catfish (Silurus glanis Linnaeus, 1758) inhabiting Çelik Lake (Adıyaman, Turkey) were investigated. The study was conducted between April 2013 and October 2013. After obtaining a blood sample from each catfish has been hematologically analyzed. Then, the water temperature, dissolved oxygen, pH, calcium, magnesium and nitrate values were determined at before breeding (April), breeding period (June - July) and after breeding of fish (October) and the impacts of these data on hematological values were investigated. According to this study, it was observed that the hematological values obtained at before breeding period, breeding and after the breeding period were affected by the water quality parameters.