Effects of different fish sizes, temperatures and concentration levels of sodium bicarbonate on anaesthesia in Mozambique tilapia (Oreochromis mossambicus)

Abstract

This study was conducted to determine the effects of different fish sizes, temperatures, and concentration levels of sodium bicarbonate (baking soda) in Mozambique tilapia (Oreochromis mossambicus). Three different body size classes of Mozambique tilapia; (i) small (0.92 ± 0.00 g, 3.4.21 ± 0.11 cm), (ii) medium (12.35 ± 2.71 g, 9.87 ± 1.23 cm), (iii) large (47.24 ± 3.12 g, 13.92 ± 2.61 cm) were subjected to three concentrations of sodium bicarbonate (30, 45, 60 g L−1) at 24, 28, or 32 °C, each replicated three times. The anaesthetic induction and recovery times were monitored at each treatment combination in five litres glass aquaria. Sodium bicarbonate proved to possess anaesthetic capacity for Mozambique tilapia, and its anaesthetic induction time was significantly affected by the concentration, water temperature, and fish size (P < .05). The induction time decreased with increase in temperature and sodium bicarbonate concentration, but increased with fish body size. Moreover, fish size and sodium bicarbonate concentration had a significant effect on the recovery time (P < .05). Inversely, anaesthetic recovery time increased with decrease in sodium bicarbonate concentration and temperature for all fish sizes; recovery time increased significantly with increased fish size (P < .05). No mortality was recorded during the anaesthetic induction and recovery time or within three days post recovery. This study indicates that, sodium bicarbonate is effective as anaesthetic in Mozambique tilapia at 45 and 60 g L−1 concentrations at all tested fish sizes and water temperature. Therefore, sodium bicarbonate is recommended as a satisfactory anaesthesia that can be used at all levels of aquaculture to improve fish welfare.