Selective predation by parrotfishes on the reef coral Porites astreoides

Abstract

Direct predation by parrotfishes (Scaridae) may be an important stressor and mortality agent for reef-building corals, yet the patterns and consequences of such predation have received little attention. In a Belizean back reef habitat, we found that parrotfish predation caused mortality of the common reef-building coral Porites astreoides with >13% of P. astreoides colonies showing partial or total colony mortality. Predation was not uniformly distributed, as completely intact colonies occurred adjacent to heavily grazed colonies exhibiting > 50% tissue lost to parrotfish predation. We examined whether differential predation on P. astreoides colonies might reflect differences in either coral nutritional quality or in coral-associated macroborers. Nutritional quality of coral tissue, measured as C:N ratios, did not differ significantly between grazed and intact P. astreoides colonies. However, significantly higher densities of coral-associated macroborers (which included barnacles, polychaetes, and vermetid molluscs) were found in grazed portions compared to ungrazed portions of the same P. astreoides colony. Thus, one explanation for selective grazing on P. astreoides colonies is that parrotfishes may be targeting coral areas with higher densities of macroboring organisms. Comparison of C:N ratios among possible dietary components suggests that macroborer consumption could potentially provide nutritional benefits to mainly herbivorous parrotfishes. These results corroborate a growing body of evidence to indicate that parrotfish predation is an important source of coral mortality, and provide a novel explanation for selective coral predation by parrotfishes.

Live coral predation by parrotfishes (Perciformes: Scaridae) in the Abrolhos Bank, eastern Brazil, with comments on the classification of species into functional groups

“…gibbus and Sc. rivulatus) also consume live corals (Bellwood & Choat, 1990;Bruggemman et al, 1994a, b;Miller & Hay, 1998;Bellwood et al, 2003;Reyes-Nivia et al, 2004;Rotjan & Lewis, 2005). Given the potential negative effects of parrotfishes' corallivory (Van Veghel & Bak, 1994;Bruckner & Bruckner, 1998;Miller & Hay, 1998;Rotjan & Lewis, 2005) there is a growing concern in understanding its relative contribution to coral fitness and survival (Miller & Hay, 1998;Rotjan & Lewis, 2005.…”

Effects of simulated fish predation on small colonies of massive Porites spp. and Pocillopora meandrina

“…The effects of localized damage on reef corals are relatively well known, usually in response to one type of mechanical damage (Nagelkerken & Bak 1998, Lirman 2000, Rotjan & Lewis 2005, Jayewardene et al 2009, Jayewardene 2010. Fish corallivores and the tissue and skeleton they remove are one of the best-known sources of damage to coral colonies (Reyes-Bonilla & Calderon-Aguilera 1999, Berumen & Rotjan 2010.…”

“…Such studies are important because the effects of fish corallivory have strong ecological implications through the consequences on growth and reproduction of coral tissue and skeleton (reviewed in Rotjan & Lewis 2005, 2008. While corals can recover from many kinds of corallivory (Rotjan & Lewis 2008, Jayewardene et al 2009), their physiological responses to these localized disturbances vary (Hall 1997, Meesters et al 1997, potentially because of differences in the capacity for tissue regeneration (Hall 1997, Meesters et al 1997, colony size, corallum morphology, tissue thickness, and polyp density (Hall 1997).…”

Coral responses to macroalgal reduction and fisheries closure on Caribbean patch reefs

“…An alternative explanation for the unexpected results is that corallivory is higher in the reserve (Rotjan & Lewis 2005 and may have an interactive effect in which the presence of macroalgae deters predation on corals by herbivores (VeneraPonton et al 2011). Rotjan & Lewis (2005) report high corallivory of Porites asteroides and this species had the lowest growth rates in the reserve, which is supported by observed higher numbers of stoplight and redband parrotfishes in the CZ versus GUZ.…”