Recovery periods of cultured spiny lobster, Sagmariasus verreauxi juveniles: Effects of handling, force feeding, exercising to exhaustion and anaesthesia on oxygen consumption and ammonia-N excretion rates

The ability of lobsters to recover from stress is an important factor influencing growth and survival in aquaculture; however, there is limited information on the metabolic responses of spiny lobsters to stress. This study determined oxygen consumption rate (ṀO₂) and ammonia-N excretion of juvenile spiny lobsters Sagmariasus verreauxi in response to handling, anaesthesia, anaesthesia then force feeding, and exercising to exhaustion in order to determine the recovery time and amount of oxygen required to recover from common sources of stress in aquaculture. Lobsters required 0.29 ± 0.24 mg O₂ g DM⁻¹ over a period of 2.5 ± 1.40 h to recover from handling. Anaesthesia with 2-phenoxyethanol immobilised lobsters but they required 0.72 ± 0.36 mg O₂ g DM⁻¹ over a period of 4.5 ± 1.77 h to recover, indicating that 2-phenoxyethanol causes substantial stress. Force feeding lobsters anaesthetised with 2-phenoxyethanol or clove oil did not result in a higher increase of ṀO₂ compared to 2-phenoxyethanol anaesthesia alone. Recovery from exercise to exhaustion required 1.84 mg O₂ g DM⁻¹ over a period of 10.17 ± 0.70 h. Ammonia-N excretion, measured 24 h post-treatment, and atomic O:N ratios were not significantly different between treatments and indicated lobsters in all groups had reached the same level of recovery 24 h post-treatment. Overall, the study demonstrated that lobsters recover rapidly from handling. Conversely, the increase in ṀO₂ induced by 2-phenoxyethanol demonstrated this is not an effective anaesthetic for reducing recovery periods and physiological stress associated with handling. However, 2-phenoxyethanol and clove oil eliminated further stress associated with force feeding, indicative of an invasive research procedure. Exercise to exhaustion resulted in the largest magnitude increase in ṀO₂ and longest recovery period. It is therefore recommended that aquaculture handling procedures take precautions to limit activity and are carried out without anaesthesia to facilitate more rapid recovery of lobsters.