Comparative Evaluation of Propofol, Eugenol and MS-222 in Yellowtail Tetra Astyanax lacustris: Anesthetic Efficacy, Physiological Responses and Recovery Dynamics

In both aquaculture and scientific experimentation, fish handling often requires anesthesia to facilitate immobilization and minimize handling-associated disturbances. This study aimed to compare the anesthetic performance of different anesthetic agents in Astyanax lacustris, assessing induction, recovery, and safety to support protocol selection for tropical freshwater fish. A total of 114 yellowtail tetra Astyanax lacustris were used, including 54 fish in a preliminary experiment and 60 fish in the main experiment, with 10 fish per concentration in each anesthetic treatment during the main experiment. Fish were exposed to different concentrations of propofol (5.0 and 6.5 mg L−1), eugenol (40 and 50 mg L−1), and MS-222 (120 and 130 mg L−1). Anesthetic efficacy and complementary physiological responses were assessed through induction and recovery times, responsiveness during recovery, opercular beat rate (OBR), hematological parameters, and plasma concentrations of glucose, lactate, and cortisol. Data were analyzed using analysis of covariance (ANCOVA) followed by appropriate post hoc tests (p < 0.05). All anesthetics successfully induced stage IV anesthesia at the evaluated concentrations, although distinct induction and recovery profiles were observed. MS-222 promoted significantly faster progression to deep anesthesia and shorter recovery times, whereas propofol induced prolonged recovery and marked reduction in OBR, with residual ventilatory depression after recovery. Eugenol showed an intermediate anesthetic profile associated with pronounced excitation during induction and an altered recovery pattern. Hematological parameters and plasma lactate concentrations did not differ significantly among anesthetic types or concentrations. Plasma glucose concentrations increased at higher anesthetic concentrations, whereas plasma cortisol concentrations differed significantly between propofol and eugenol groups (p < 0.05). Overall, the findings demonstrate that propofol, eugenol, and MS-222 produce distinct anesthetic and ventilatory responses in A. lacustris, highlighting the importance of selecting anesthetic protocols according to the intended experimental or handling procedure.