A ‘Field of Mouths’: Damselfishes in the Intertidal of Heron Island Cay, Great Barrier Reef

The study was undertaken in the intertidal zone on the lee side of Heron Island cay (southern Great Barrier Reef) where there is a high density of branching corals. We investigated the influence of coral colony size on the diversity of damselfish species (Pomacentridae) associated with the branching corals. Forty coral colonies were marked and the associated pomacentrids photographed and identified. Eleven or twelve species were identified and there were up to eight species associated with a coral colony. The relationships between diversity of fi sh species and coral colony area, and coral colony perimeter were very significant. Plankton samples in the vicinity of the fringing reef are sparse during the day when the fish are feeding compared to the rich samples at night when they aren't feeding, suggesting a substantial impact on the zooplankton content of the water fl owing over the fi shes' habitats. In contrast to the ‘wall of mouths' on the windward crest of a patch reef, it is suggested that these pomacentrid inhabitants of the shallow waters fringing Heron Island cay constitute a ‘field of mouths'. During the day, they trap and retain the allochthinous organic material that flows across the shallow coral reef and act as a source of nutrients for this coral reef ecosystem.