Comparative efficacy of benzocaine, tricaine methanesulfonate and eugenol as anesthetic agents in the guppy Poecilia vivipara

The aim of this study was to evaluate the anesthetic efficacy and determine the lowest effective concentration in the guppy, Poecilia vivipara. Fishes were exposed to benzocaine, tricaine methanesulfonate and eugenol at three different concentrations. After induction, they were transferred to an aquarium free of anesthetic for evaluating their recovery time. At the lowest concentration of the three anesthetics (50 mg L−1), fish did not reach complete induction. Time to accomplish a light sedation stage was significantly negative-related with concentration using tricaine (145 ± 13.4 s with 50 mg L−1 to 4.7 ± 0.7 s with 200 mg L−1) and benzocaine (152.8 ± 13 s with 50 mg L−1 to 4.0 ± 0.9 s with 200 mg L−1). For eugenol, significant differences were found between the lowest concentration, 50 mg L−1 (241 ± 57.6 s) with 100 mg L−1 (13.3 ± 3.9 s) and 200 mg L−1 (9.5 ± 2.6 s). Recovery times were significantly longer (P