A coral spawning calendar for Sesoko Station, Okinawa, Japan

Sesoko Station, Okinawa, has been the site of many significant advances in coral reproductive research and it continues to be a preferred destination for both Japanese and international researchers. Consequently, there are decades of spawning observations, which we present and explore here with the aim of making it easier to predict when species spawn at Sesoko Station. The data include over 700 spawning observations from 87 species of reef-building hermatypic corals. Almost all spawning occurred between dusk and dawn, with most spawning activity concentrated in the 2 to 4 hours after sunset. Some phylogenetic patterns were evident: most Acropora species spawn on or around the 6th full moon after December 21st (the northern hemisphere winter solstice); spawning in common species of merulinids and Porites appears to be concentrated around the 7th full moon and spawning in the fungiids around the 8th and subsequent full moons. The night of peak spawning with respect to the night of the full moon varied considerably among years in common Acropora species, but was dependent on the calendar date of the full moon in May or June. Therefore, despite an extended spawning season of over three months and considerable variation in the calendar date of spawning in many species among years, the month and night of spawning are reasonably predictable for many species enhancing the value of Sesoko Station as a site for coral reproductive research.