The effectiveness of tricaine, benzocaine, clove oil, and menthol as anesthetics for lambari-bocarra Oligosarcus argenteus

The efficacy of four anesthetic agents was evaluated in the lambari-bocarra Oligosarcus argenteus. Adults (weight, 11.3 +/- 3.3 g; length, 10.2 +/- 1.1 cm) were exposed to tricaine (25, 50, 75, 100, 125, 150, and 175 mg L-1), benzocaine (25, 50, 75, 100, and 125 mg L-1), clove oil (25, 50, 75, 100, and 125 mg L-1), and menthol (25, 50, 75, 100, and 125 mg L-1) for inducing deep and surgical anesthesia. The anesthetic effect was evaluated by measuring time to induction stages, recovery time, appetite return, and 96-h mortality rate. For all anesthetics, the induction time decreased as their concentration increased. The anesthetics had no effects on fish mortality, and appetite return occurred before 24 h. The tricaine induced deep and surgical anesthesia in 3 min at concentrations ranging from 100 to 175 mg L-1 and from 150 to 175 mg L-1, respectively. The highest concentrations of tricaine, 150 and 175 mg L-1, provided shorter induction times and recovery times were not different when using concentrations ranging from 100 to 175 mg L-1. The benzocaine concentrations between 75 and 125 mg L-1 and 100 and 125 mg L-1, respectively, provided deep and surgical anesthesia induction times below 3 min. Recovery time was superior at benzocaine concentrations of 50 to 100 mg L-1. Clove oil effectively induced anesthesia at lower concentrations, with 50 and 75 mg L-1 inducing deep and surgical anesthesia. The recovery times were not different when using concentrations ranging from 25 to 125 mg L-1. All menthol concentrations tested effectively induced deep anesthesia. The menthol concentration of 75 mg L-1 effectively induced surgical anesthesia in 3.62 min, longer recovery times at 25 and 50 mg L-1. In conclusion, the tested anesthetics effectively induced anesthesia in lambari-bocarra, with deep anesthesia being induced at concentrations of 100 and 75 mg L-1 for tricaine and benzocaine, respectively, and 50 mg L-1 for clove oil and menthol. For surgical anesthesia, the recommended concentrations are 150, 100, 75, and 100 mg L-1 for tricaine, benzocaine, clove oil, and menthol, respectively.