Cultivation of sponge Haliclona simulans juveniles in a floating sea raft

Abstract Large-scale mariculture of a marine sponge requires a sustainable seed stock that can be raised artificially. To find the optimized breeding methods for Haliclona simulans juveniles, a study with three stages, starting from free swimming larvae, was performed in a field laboratory placed on a floating sea raft. In the first step, six different substrates were compared, and polystyrene plastic petri dishes were found to be the optimal substrates for settlement and metamorphosis of H. simulans swimming larvae. Then, in the second stage, 30-days growth experiments with 20 conditions were used for the larvae settled on plastic petri dishes. The optimized devices and conditions suited for the early-stage cultivation of sponge larvae were obtained. In the final stage, a 4-months growth experiment was performed with the guidance of the optimized conditions acquired from the former stages. At the end of the experiment, the group with the highest growth rate achieved an average length of 18.44 ± 10.73 mm, and the largest juvenile length reached 33.4 mm, equivalent to a 45-folds increase in length or over 20,000-folds increase in volume when compared to the larvae that just settled. Thus, we established a feasible and low-cost sponge-larval mariculture pattern, upon which the culturing procedures can be improved and the sustainable seed stock needed for sponge large-scale culture becomes possible.