Development of ceramic settlement devices for coral reef restoration using in situ sexual reproduction of corals

A ceramic coral settlement device (CSD) was developed to raise juvenile corals in situ in preparation for transplantation. The CSD is designed to be deployed in the water before mass spawning of corals, allowing larvae to settle and grow on the CSD before it is fixed to the reef structure. CSDs were aggregated and fixed on 0.2-m2 frames (either 648 or 720 CSDs per frame) and deployed in the Sekisei Lagoon around the full moons of April and May in 2002. Seven frames were collected in August 2002 and settled corals were counted in the laboratory. The maximum number of coral colonies settled on CSDs in one frame was 617, with 94% belonging to the genus Acropora. The aggregated CSDs successfully functioned as a coral settlement substratum, with more appropriate arrangement of CSDs on the frame, enabling greater exposure to sunlight and currents, which is expected to increase the amount of settlement.