This study investigated the effects of oregano (Origanum vulgare) essential oil (OEO) anaesthesia and stress-related physiological parameters in tilapia mossambicus (Oreochromis mossambicus) post-juveniles. Fish were subjected to different concentrations of OEO (25, 50, 100, and 150 μL L−1) to assess the effects of the anaesthesia and recovery time. A second experiment subjected fish to other handling treatments, including a control (no OEO exposure), ethanol solution, 25 μL L−1 (low effective anaesthesia concentration of OEO), and 100 μL L−1 high effective anaesthesia concentration of OEO) for 10 min to assess the haemato-biochemical indices and survival rate at 0 h and after 24 h. Moreover, all the tested OEO concentrations induced anaesthesia in the studied fish, where the anaesthesia induction time decreased with increased OEO concentrations. Meanwhile, the inverse was reported for recovery time. Based on the ideal anaesthetic criteria, 50 μL L−1 and 100 μL L−1 were the suitable concentrations that could be recommended for quick anaesthesia. However, according to the haemato-biochemical parameters and survival results, 25 μL L−1 was safe to anaesthetise tilapia mossambicus for 10 min and could be recommended for time-consuming fish-handling procedures. Future studies should investigate multiple factors that influence anaesthesia in fish for better optimisation of OEO in tilapia mossambicus.

This study aimed to study the effectiveness of different concentrations of sodium bicarbonate (baking soda) combined with acetic acid (vinegar) in three spotted tilapia (Oreochromis andersonii) fingerlings. Fingerlings (body weight 0.82 ± 0.00 g, and body length of 3.91 ± 0.03 cm) were subjected to three concentrations of sodium bicarbonate (30 g/L, 40 g/L and 60 g/L) combined with three concentrations of acetic acid (30 ml/L, 45 ml/L and 60 ml/L), each replicated five times to assess the anaesthesia induction and recovery time. Sodium bicarbonate and acetic acid induced anaesthesia in three spotted tilapia fingerlings regardless of the concentration used. However, high concentrations induced anaesthesia within a short period of time. Meanwhile, the full recovery time increased with concentration combinations. In essence, low concentrations of sodium bicarbonate and acetic could be recommended for anaesthetizing three spotted tilapia fingerlings. However, more studies on sodium bicarbonate and acetic acids as anaesthetics in aquaculture and fisheries is deemed necessary.

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