Recovery of the western rock lobster, Panulirus cygnus, from emersion and handling stress: the effect of oxygen concentration during re-immersion

The effect of dissolved oxygen concentrations (110-120, 90-100, 70-80, 50-60, 30-40 and 10-20% saturation) on recovery of Panulirus cygnus from a period of activity/emersion was investigated. Biochemical disturbances induced in P. cygnus by emersion and handling included a large decrease in the hemolymph pH (0.7 units) and an increase in the hemolymph lactate concentration (2.44 mmol L-1). Re-immersion resulted in very high rates of oxygen consumption (up to 2.5 times the pre-emersion rate), elevated hemolymph glucose (1.1-4.5 mmol L-1) and further increases in hemolymph lactate (2.7-11.1 mmol L-1), with actual concentrations dependent on the dissolved oxygen concentration. Water oxygen concentrations of 50-60% saturation or less slowed the rate of recovery; all lobsters recovering in water with 10-20% oxygen saturation died within 12 hours. Based on the rate of recovery of physiological parameters, lobsters should be allowed to recover for a minimum of eight hours between stress episodes, whilst maintaining an oxygen concentration of 70-80% saturation or above.