Analysis of primary and secondary stress responses in bighead carp ( Hypophthalmichthys nobilis ) by anesthetization with 2-phenoxyethanol

The main objective of the present study was to shed light on the effects of 2-phenoxyethanol on possible primary (cortisol level) and secondary (hematological indices and glucose level) stress responses and changes in the activity of metabolic enzymes (AST, ALT and ALP) in bighead carp (Hypophthalmichthys nobilis). The fish were exposed to 0.1, 0.3, 0.5, 0.7 and 0.9 ml L-1 of 2-phenoxyethanol. 2-Phenoxyethanol induction and recovery times were 115-595 and 29.66-179.3 s, respectively. At a concentration of 0.1 ml L-1, the anesthetic failed to induce deep anesthesia. The lowest effective concentration of 2-phenoxyethanol was determined to be 0.7 ml L-1, whereas 0.9 ml L-1 was found to be the most effective one. Data showed that RBC, WBC, hemoglobin and hematocrit values were significantly high in some treatments compared to the control. MCV and MCH contents decreased significantly. MCHC, ALP, AST and ALT did not vary significantly. Plasma glucose and cortisol levels were significantly high compared to the control (in some doses). Moreover, Na+, K+, Ca2+, Mg2+ and Cl- did not vary significantly. Findings suggest that blood parameters were affected by anesthetizing bighead with 2-phenoxyethanol at 0.9 ml L-1 to the lowest extent.