A novel rearing system to mitigate cannibalism in juvenile ornate spiny lobster, Panulirus ornatus

Development of larval rearing technology for the ornate spiny lobster, Panulirus ornatus , has laid the foundations for sustainable commercial aquaculture. However, low survival during juvenile culture due to cannibalism represents a considerable bottleneck to advancing production, with survival of <25 % typical during early juvenile rearing (instar J2 – J10). Cannibals typically target lobsters during and shortly after moulting when they are highly vulnerable prior to their new carapace hardening. Mitigating cannibalism of moulting lobsters is fundamental to improving survival and advancing commercial farming. This study tested a novel culture system that encourages separation of inter-moult and pre-moult early juvenile (instar J2 – J8) lobsters, referred to as the Daily Migration System (DMS). Using feed cues to trigger one-way migration across a divider in the tank, separating the tank into a feeding side for inter-moults and non-feeding side for pre-moult lobsters to moult safely. Two stocking densities (Low Density 111 m −2 and High Density 222 m −2 ) were assessed in DMS tanks and Control tanks. The DMS tanks effectively promoted migration, with 92–94 % of lobsters crossing the tank divider daily. Migration success was not different between the two density treatments (Wilcoxon signed-rank test, V = 13,406, P = 0.1). A greater number of moults (exuviae) were observed on the non-feeding side (365) compared to the feeding side (105) for both stocking densities (chi-square = 0.94, DF = 1, P = 0.005). Therefore, approximately 61 % of lobsters were successfully isolated from inter-moult lobsters when moulting, therefore protecting them from cannibalism. Highlighting the effectiveness of DMS tanks in separating pre- and inter-moult lobsters. The occurrence of moults on both sides of DMS tanks indicates further system and or operation refinement is required. The DMS significantly improved survival over 63 d of experimental culture, with the highest survival recorded in the Low Density treatments (78 ± 6 %) followed by Low Control (52 ± 7 %), compared to High Density DMS (47 ± 5 %), and High Density Control (29 ± 5 %). Final carapace length and wet weight gain did not differ among treatments, although Low DMS tanks achieved the greatest overall biomass gain (973 ± 250 %). These results highlight the potential of the DMS to mitigate cannibalism and improve survival and biomass yield during early juvenile rearing of P. ornatus . With further refinement, the DMS could be effectively integrated into onshore commercial culture of juvenile P. ornatus and has potential application for culture of other cannibalistic decapods. • Development of a novel system to reduce cannibalism in juvenile Panulirus ornatus. • DMS used feed cues to separate pre- and inter-moult lobsters. • DMS improved survival, with lower density survival higher than high density. • Biomass gain was greatest in high density DMS tanks. • Improved survival and biomass gain proves potential for onshore commercial culture.