Efficiency of clove oil as an anesthetic in blue swimming crab Portunus segnis

Abstract

Objective: Anesthetics are essential for reducing stress, facilitating handling, and preventing injury in aquatic animals. They are extensively employed in tagging and blood and hemolymph sampling. However, synthetic anesthetics can adversely affect the physiology and safety of living organisms. This study aimed to evaluate the efficacy of clove oil as a natural anesthetic in reducing handling stress in blue swimming crabs Portunus segnis by evaluating the effects of different concentrations on anesthetic induction and recovery times. Methods: We compared three doses of clove oil (150, 300, and 450 μL/L) to assess anesthetic induction and recovery times of the crabs. Samples were collected from the northern Persian Gulf coastline (Hormozgan, Iran). A total of 45 crabs (weight [mean ± SD] = 51.24 ± 3.08 g; carapace width = 8.61 ± 0.17 cm) were exposed to the selected concentrations. After the anesthetic bath, anesthesia times (stages A1, A2, and A3) and recovery times (stages R1, R2, and R3) were individually recorded. Results: Required optimal times for all anesthesia stages were approximately 283 ± 13, 423 ± 22, and 856 ± 61 s, whereas the times for recovery stages were 296 ± 8, 455 ± 16, and 753 ± 27 s for the three doses. Deep anesthesia was observed in all treatments, and no mortality was recorded during the experiment or the 48-h observation period. Data analyses indicated a significant difference between treated crabs’ induction and recovery times at the selected doses. The induction and recovery times were positively correlated with the weight of crabs. Conclusions: The findings of this study demonstrate that clove oil at a concentration of 300 μL/L is an effective anesthetic for blue swimming crabs, providing a practical solution for minimizing handling stress in aquaculture. The natural origin and safety profile of clove oil make it a suitable alternative to synthetic anesthesia. Future research should explore the long-term effects on crab health and meat quality to further refine the use of clove oil in commercial settings.