FISHERIES SCIENCE 2005; 71: 263–270 Blackwell Science, LtdOxford, UKFISFisheries Science0919-92682005 Blackwell Science Asia Pty LtdApril 2005712263270Original ArticleCulture of coral by sexual reproductionM Okamoto et al. *Corresponding author: Tel: 81-3-5463-0485. Fax: 81-3-5463-0518. Email: okamotom@s.kaiyodai.ac.jp Received 19 May 2004. Accepted 29 September 2004. A basic experiment of coral culture using sexual reproduction in the open sea Mineo OKAMOTO, 1 * Satoshi NOJIMA, 2 Yasuo FURUSHIMA 3 and William C. PHOEL 4 1 Tokyo University of Marine Science and Technology, Tokyo 108-8477, 2 AMBL, Kyushu University, Kumamoto 863-2507, 3 JAMSTEC, Yokosuka 237-0061, Japan and 4 Underwater Research Foundation International Inc., New Jersey 08753, USA ABSTRACT: Coral larvae, produced from a mass spawning event, were successfully settled on special stone settlement sticks and raised in situ for eventual transport to other reefs. The test area, Sekisei lagoon, Okinawa Prefecture, Japan, is located close to the warm Kuroshio current and is sur- mised to be the source from which major Japanese corals are derived. A total of 131 settlement sticks, with small holes in their sides to increase protection from grazing (4 mm in diameter and approxi- mately 5 mm deep), were deployed in the lagoon the day before the coral’s mass spawning. After 3 months, 61 sticks were recovered containing 71 corals, mostly in the holes. After 1 year, three corals were confirmed to be growing well and extending outside the holes of the three sticks out of 70 sticks left in the water at the lagoon site. They survived two potentially lethal conditions, that is, high water temperatures with associated extensive coral bleaching and continuous grazing pressure from pred- ators. This procedure is applicable for large-scale coral transplantation, not only in Japan but also in other tropical countries. KEY WORDS: coral, mass spawning, settlement, sexual reproduction, transplantation. INTRODUCTION Coral reefs in the world have suffered drastic declines in the past several decades due to many stresses but especially climate change, pollution and overfishing. 1–4 Mass coral bleaching involving many of the world’s coral reefs in 1997–1998 high- lighted a serious potential impact on coral reef ecosystems. 5 The major coral reefs of Japan are distributed along the warm Kuroshio current. The largest coral reef in Japan is Sekisei lagoon, which is located near the origin of the Kuroshio. 6,7 This highly diverse area has recorded 363 species of her- matypic corals. 8,9 Japanese coral reefs suffered severe bleaching in the summer of 1998 and again in the summer of 2001. In 1998, 90% of the corals around Okinawa Island (450 km north-west of Sekisei lagoon) died due to the effect of the bleach- ing event, 10,11 and the remaining corals were dam- aged again in 2001. The damage to the corals in Sekisei lagoon was not as severe as the damage to the corals of Okinawa Island where those corals are facing extinction due to the effect of repetitive bleaching. Sekisei lagoon is surmised to be the main source of coral larvae for the Japanese Islands along Kuroshio and there is concern that the dis- appearance of the corals in Sekisei lagoon may lead to the extinction of the major Japanese coral reefs. The recovery of corals by the transplantation of coral fragments has been examined, 2,12 however, this method has become difficult to apply for Japanese coral reefs. Coral community as fragment donors is decreasing drastically in Japan except Sekisei lagoon. Thus, the recruitment of corals by mass spawning is thought to be very important for the prevention of local extinction. 13–18 Our experiment was to obtain coral larvae through natural mass spawning and raise them in situ for future transplantation to coral reefs that have been decimated by bleaching. LOCATION, MATERIALS AND METHODS Sekisei Lagoon is located between Ishigaki-jima and Iriomote-jima of the Yaeyama Islands in Okinawa Prefecture, Japan (Fig. 1). The dimensions of the lagoon are approximately 25 km east and