World Aquaculture 2023

May 29 - June 1, 2023

Darwin, Northern Territory, Australia



 Eleanor L. Spencer, Quinn P. Fitzgibbon, Ryan D. Day, Andrew J. Trotter, Gregory G. Smith.

 Institute for Marine and Antarctic Studies (IMAS),

 University of Tasmania, Private Bag 49,

Hobart, TAS, 7001, Australia.

The tropical rock lobster, Panulirus ornatus, is emerging as an important species for onshore aquaculture development. Commercial grow out of lobsters from the juvenile to harvest phase are likely to be conducted in outdoor raceways or pond culture systems in tropical regions of Australia. In these areas, climate has a large impact on the prevailing environmental conditions, this includes torrential rain and high ambient air temperatures impacting pond salinity for hours to weeks. The salinity tolerance of P. ornatus with respect to specific moult stage survival, physiology and blood biochemistry were previously unknown.

This study investigated Lethal Concentration of salinity which caused 50% mortality (LC50) and haemolymph biochemistry of P. ornatus juveniles when acutely exposed for 48 h to different salinities (10, 15, 20, 25, 30, 34, 40, 45, 50, 55, and 60 ppt) at three stages of the moult cycle (post-, inter- and pre-moult). Moult stage significantly impacted the survival of lobsters at low salinity (<34 ppt), which ranged from LC5048=12.5 ppt for post-moult lobster to LC5048=20.0 for pre-moult (Figure 1). There was no significant effect of moult stage on high salinity (>34 ppt) tolerance of lobsters which ranged from LC5048=50.5 - 54.5 ppt. Haemolymph osmolarity showed inter-moult lobsters to be weak hyper-regulators, with post- and pre-moult being hyper-osmoconfromers. Moult-stage significantly affected haemolymph oxyhaemocyanin and protein concentration, with pre-moults having the highest values and post-moult the lowest, with no impact of salinity treatments. At 50, and 55 ppt, oxyhaemocyanin was significantly elevated compared to 34 ppt with no effect of the moult stage. While at 55 ppt, superoxide dismutase (SOD) activity was significantly lower compared to 25, 40, 45, and 50 ppt with no effect of moult stage. Our results suggest a salinity tolerance range between 20 - 40 ppt; beyond this, lobsters experience oxidative stress due to the breakdown of osmoregulation. This study provides an improved understanding of the survival and physiological impacts of salinity change on P. ornatus that is essential for optimising productivity protocols for the onshore aquaculture of the species.