Stress Response and Blood Characteristics of Channel Catfish (Ictalurus punctatus) after Anesthesia with Etomidate

Abstract

Continuous anesthesia of channel catfish (Ictalurus punctatus) with 0.6 mg/L etomidate for 96 h caused a small but statistically significant decrease in plasma protein concentration at all sampling periods. Hemoconcentration, indicated by increased total erythrocyte count, hematocrit, and hemoglobin, resulted from anesthesia with 1–4 mg/L etomidate for 30–180 min. Periodic removal of fish from 400-L troughs stressed other unanesthetized fish in the trough causing significantly increased plasma corticosteroid, glucose, and protein concentrations. Anesthetized fish were not stressed by the periodic sampling. Fish anesthetized with 3 mg/L etomidate and then confined in a net for 10 min had reduced plasma Cortisol response and no significant plasma glucose increase compared with unanesthetized controls. Anesthesia did not prevent hyperchloremia that developed 3 h after the 10-min confinement. No histological changes were found in fish anesthetized with etomidate. Anesthesia with etomidate before netting could be useful when handling fish because of the reduced stress response.