The Giant Triton may affect aggregation and fertilization success of the Crown of Thorns Starfish. 1. General Background Outbreaks of the crown of thorns starfish (Acanthaster planci) have been studied for many years throughout the Indo-West Pacific region (Moran, 1986) and although many explanatory hypotheses have been proposed we do not understand why outbreaks of this starfish occur on some reefs while, on other nearby reefs, this starfish maintains a stable, low population density. On the Great Barrier Reef and elsewhere, most starfish research has centered on establishing the scale of Acanthaster outbreaks and the effect of Acanthaster predation on the coral reef community. The giant triton (Charonia tritonis) and other members of the genus Charonia are known predators of many species of starfish (Chesher, 1969; Endean, 1969; Laxton, 1971; Noguchi et al., 1982; Percharde, 1972) but there are few examples of other species predominantly preying on starfish (Harrold and Pearse, 1987)...