Efficacy of Hesperozygis ringens essential oil as an anesthetic and for sedation of juvenile tambaqui (Colossoma macropomum) during simulated transport

Abstract

This study evaluated the anesthetic and sedative effects of the essential oil of Hesperozygis ringens (EOHR) on juveniles Colossoma macropomum. Experiment 1 exposed juveniles (3.35 ± 0.73 g) to 0 (control), 75, 150, 300 and 450 µL L^− 1 of EOHR, with 10 replications each. Induction time showed a quadratic effect (R² = 0.8628), while recovery time showed a direct linear effect (R² = 0.7527). Concentrations between 150 and 450 µL L^− 1 EOHR are therefore recommended for use as anesthetic for C. macropomum. Experiment 2 evaluated 0, 5, 15 and 30 µL L^− 1 of EOHR for two periods of transport (4 and 24 h) of juveniles (1.46 ± 0.58 g) in 32 plastic bags (30 × 40 cm) containing 1 L of water, 2/3 of pure oxygen with 10 fish per bag. All EOHR treatments had lower dissolved oxygen (DO) after 24 h, while 15 and 30 µL L^− 1 EOHR had lower non-ionized ammonia after 4 and 24 h. Experiment 3 used the same procedures as Experiment 2 for 24 h of transport with juveniles (1.77 ± 0.58 g) in 16 plastic bags at the same density (10 fish L^− 1). Concentrations of 15 and 30 µL L^− 1 EOHR had lower pH after 24 h and all EOHR treatments had lower DO. No mortality was observed. Experiment 4 tested the same concentrations of EOHR evaluated in Experiment 2 but using 16 plastic bags without fish. The concentrations of 15 and 30 µL L^− 1 EOHR had lower DO and pH after 24 h.