The Tropical Rock lobster, Panulirus ornatus, is a promising species for onshore aquaculture development. Grow-out from juvenile to harvest phase will likely occur in outdoor pond-culture systems in Queensland, Australia. A region that experiences extreme climatic events, including torrential rain and high ambient air temperatures impacting pond salinity.
Following exposure to four different salinities (25, 30, 34, and 40 ppt) for 75 days, the growth, metabolism, and haemolymph physiology of juvenile lobsters were unaffected in salinities between 25 and 34 ppt. Juvenile P. ornatus had a reduced ability to tolerate salinities above 34 ppt, leading to 80% mortality at 40 ppt. At 40 ppt, all physiological parameters examined showed significant signs of physiological stress. Haemolymph osmolarity indicated P. ornatus to be a weak hyper-regulator, remaining isosmotic with the ambient salinity at low salinities, but at 40 ppt, becoming hyper-osmotic to the line of the ambient. This suggests that P. ornatus's inability to regulate the ion influx into their cellular membrane at high salinity was the cause of mass mortalities.
This study provides an improved understanding of salinity change's survival and physiological impacts on P. ornatus, which is essential for optimising productivity protocols for the onshore aquaculture species.