Ecological drivers of parrotfish coral predation vary across spatial scales

Abstract

Parrotfishes (Labridae: Scarini) are widely recognized for their important functional role in reducing coral-algae competition by grazing algae, yet some species are also coral predators (corallivores) and thereby have direct negative impacts on corals they prey upon. To better understand the ecological drivers of parrotfish corallivory intensity, we compared patterns of relative predation scar size and abundance across spatial scales from individual coral colonies (<1 to several meters in size), to reefs within islands (1 to 10s of km), to 4 regions across the Greater Caribbean (100s to 1000s of km) including Panamá, Florida, St. Croix, and Bonaire. Across reef sites, there was a positive correlation of both parrotfish density and biomass with the relative coral area preyed upon, but not predation scar abundance. While there was no apparent site-level effect of coral cover on corallivory intensity, we found that the abundance of colonies preyed upon was positively correlated with both coral diversity and the proportional cover of frequently targeted coral taxa within localized 30 m2 reef areas. At the scale of individual coral colonies, we found that while numerous coral taxa were preyed upon, corallivory was concentrated on a few species across regions, such as Orbicella spp., Porites spp., and Stephanocoenia intersepta. Our findings suggest that while increased parrotfish densities may result in an increased coral area preyed upon across reefs, corallivory intensity within reefs may decrease in response to declines in the cover of frequently targeted coral taxa and overall coral diversity.Spanish and Papiamentu versions of the abstract are provided in the Supplement at www.int-res.com/articles/suppl/m740p145_supp.pdf