Production of coral colonies for outplanting using a unique rearing method of donor colonies at Onna Village, Okinawa, Japan

Abstract

About 20,000 coral colonies (＞8 cm in diameter) for outplanting are produced annually at Onna Village Fisheries Cooperative in Okinawa using a novel method for aqua- culture of coral. Corals to be used as donors are produced from small coral fragments (about 5 cm in length) taken from natural colonies and reared on top of the iron poles (19 mm in diameter) 50 cm above a sand and gravel seafloor situated in the back-reef moat at a depth of 2-3 m (Fig. 1A). When they have grown to about 30 cm in dia meter, 60% of the each colony is pruned, producing about 30 small fragments. The small fragments are attached to cy- lindrical substrates made of Mug White (Magnesium con- taining soil hardening agent, Patent PCT/JP01/01259) using thin stainless steel wire (Fig. 1B), and kept in water tanks on land for about 1 week. Subsequently, they are farmed in fixed underwater nurseries (about 40 cm above the seafloor) (Fig. 1C) for more than 3 months until the corals have self-attached to the substrates and attained a suitable size (＞5 cm) for outplanting to denuded reef areas. In the Coral Reef Preservation & Rehabilitation Project of Okinawa Prefecture (public works since 2010), 10440 frag- ments of 13 species were outplanted on the reefs areas off Onna Village in 2014.