Butterflyfishes exhibit species-specific responses to changes in Pacific coral reef benthic communities

Many butterflyfish species exhibit feeding preferences for scleractinian corals that represent a continuum from facultative to obligate strategies, and which affect their predicted responses to temporal and spatial changes in coral community structure. Less frequently studied are interactions between butterflyfishes and soft corals, even though the latter represent significant habitat and energetic resources on Indo-Pacific coral reefs. Changes to the benthic community structure of three disjunct back-reef communities on the leeward side of Guam were monitored over two decades, from 1994 to 2014. These communities include a reef that has remained stable and relatively pristine through time, a reef that is significantly impaired but has remained stable over time, and a reef that has experienced significant changes in response to anthropogenic and natural disturbances during this period. Density and behavior of six species of butterflyfishes, including an obligate hard corallivore, two soft corallivores, and three generalists of varied dietary breadth, were recorded at each of the sites in 1994, 2004, and 2014. The populations of butterflyfishes varied through time and space, and there were significant changes in foraging behaviors, largely associated with changes in the soft coral community. Moreover, the soft corallivores exhibited differential prey preferences, some of which were directly attributable to their ability to handle soft coral chemical defenses, while others appeared to be more opportunistic. Given this tight coupling between butterflyfishes and soft corals, this resource needs to be a focus of future studies.