Eugenol as anesthetic for Piaractus mesopotamicus

Abstract

The different practices used in fish breeding require intense handling, leading to fish stress. The use of anesthetics is important to overcome this problem. This study aimed at evaluating the impact of eugenol on the induction and anesthetic recovery of Piaractus mesopotamicus from different weight classes. An experiment was carried out in a 5x5 factorial scheme, consisting of five weight classes (50 ± 5.61 g, 100 ± 9.36 g, 150 ± 12.29 g, 200 ± 12.73 g and 250 ± 18.77 g) and five eugenol concentrations (40 mg L^-1, 80 mg L^-1, 120 mg L^-1, 160 mg L^-1 and 200 mg L^-1). The anesthesia induction was divided into four stages, according to the behavior of the anesthetized fish, being the duration of each stage recorded, and the desensitization moment and recovery time evaluated. A quadratic effect was observed at the anesthetic induction time, i.e., when the dose increased, the induction time decreased, tending to stabilize for increasing doses. The best results for anesthetic induction were observed at the 175 mg L^-1, 208 mg L^-1, 203 mg L^-1, 240 mg L^-1 and 225 mg L^-1 concentrations, respectively for the 50 g, 100 g, 150 g, 200 g and 250 g weight classes. No interaction between the shortest induction time and the shortest recovery time was observed. Thus, the doses which provided a lower induction time for the weight classes range between 175 mg L^-1 and 240 mg L^-1.