ABSTRACT

At least since the time of Darwin, there has been controversy about the impact of fi shes on corals. Although Darwin (1845) reported that two species of parrotfi shes feed exclusively on coral and that their feeding behaviour produced copious amounts of sediment, Dana (1849) countered that he had never seen grazing by fi shes on corals and that fi sh feeding could not produce the volume of sediment present on coral reefs. Since that time many species have been described to feed on corals, although the type of feeding and potential impacts on the corals themselves vary tremendously among corallivores. Even within the butterfl yfi shes (which have the greatest number of corallivorous species), the mode of feeding (ranging from extensive scraping to nipping of coral tentacles) and the extent of reliance on corals for food varies greatly (Cole and Pratchett, Chapter 5). There is no doubt that coral feeding can have a dramatic impact on coral populations, for example when there is an outbreak of corallivores, as has been seen repeatedly with population explosions of crown-of-thorn seastars (Branham et al., 1971; Endean, 1973; Glynn, 1974) or coral-feeding snails (Moyer et al., 1982). In these cases, total mortality of colonies can occur, and the recovery of the coral community may require decades (Moran, 1986; Endean and Cameron, 1990; Colgan, 1987; Sano, 2000). However, many forms of

University of Hawai’i West O’ahu, Pearl City, and Hawai’i Institute of Marine Biology, Kāne’ohe, Hawai’i. E-mail: fcox@hawaii.edu

corallivory have less visible impacts on coral populations. Harmelin-Vivien and Bouchon-Navaro (1981, 1983) estimated that consumption by the butterfl yfi sh populations at Aqaba was 10 g per 1000 m2 each day and at Moorea 28 g per 1000 m2 each day. They suggested that this low rate of coral feeding and the territorial behaviour of these butterfl yfi sh species prevented signifi cant impacts on the coral food resource. Reese (1991) suggested that although corals are a relatively poor food resource, corals are spatially and temporally stable in abundance and their aggregated distributions and ability to regenerate rapidly allow butterfl yfi shes to sustainably harvest coral resources within a defendable territory.