Selective feeding by corallivorous fishes neither promotes nor reduces progression rates of black band disease

Black band disease (BBD) is a virulent coral disease, and although its microbiology has been studied extensively, the aetiology of BBD remains poorly understood. Here we used aquaria and field experiments to determine if feeding on BBD lesions by corallivorous fishes influences disease progression rates. Although selective predation on lesions was observed in both controlled laboratory experiments and field-based observations, we found no evidence that fish feeding either reduced or enhanced progression rates of BBD. Variability in disease progression rates in the field was explained by variation among coral colonies (24.46%) and among sample days (37.77%) rather than by predation treatment (< 0.1%). Also, disease progression rate was significantly correlated with the width of the disease band. This suggests that properties of the disease band, potentially the complexity of the microbial community forming the band, influence rates of tissue loss. Results highlight that natural variation in host resistance and dynamics of the disease band play a greater role in BBD progression rate than selective feeding by corallivorous fish.