Recruitment patterns of scleractinian corals: A study of three reefs

Racks of settlement plates were placed in forereef and backreef sites at three reefs offshore from Cairns (Green, Michaelmas and Upolo Reefs) during winter 1985, summer 1985/86, and winter 1986. Over 2200 spat were recorded on the summer plates, while 61 and 220 spat were found on the winter plates in the two years. Acroporid spat were generally dominant on summer plates, except for Upolo Reef where pocilloporid spat were the most abun'dant at all times of year. Most spat settling in winter at all reefs were of the family Pocilloporidae. Summer spat settlement showed significant variation in numbers between reefs and between forereef and backreef sites on each reef, with the greatest number on backreef sites. Highest recruitment was at Green Island reef despite the relatively depauperate adult fauna on that reef; this suggests that inter-reef dispersal may be the dominant factor in determining the number of recruits. Hypothesized dispersal paths of coral planulae in the region are derived from data on postspawning oceanographic conditions, and testable predictions are made for future recruitment patterns in this reef set.