摘要：Abstract Surgeonfishes (Acanthuridae) are an important group of herbivores that are abundant on reefs globally. Acanthurids consume macroalgae that can compete with corals for space, turf algae that can proliferate on degraded reefs, and detritus that may smother adult corals or inhibit settlement. For these reasons, they are of particular interest at present to resource managers seeking to restore and conserve reefs that are facing a myriad of stressors. To contribute to our understanding of the diet breadth and potential vulnerability of these important fishes, we employed metabarcoding to identify and compare the algal diets of two common Hawaiian surgeonfishes, the convict tang or manini (Acanthurus triostegus) and the brown surgeonfish or maʻiʻiʻi (A. nigrofuscus). These species serve important biological and cultural roles in Hawaiian coral reef ecosystems, and manini, in particular, constitute an essential component of traditional Hawaiian diets. Although diet richness was not significantly different between the species, with 64 unique taxa identified from the gut contents of 89 A. triostegus and 57 taxa from 73 A. nigrofuscus, A. nigrofuscus exhibited greater diet diversity as measured by the Simpson's Diversity Index. A. nigrofuscus had a greater relative read abundance of brown algae, cyanobacteria, and material from the epilithic algal matrix. A. triostegus had a taxonomically more specialized diet, consuming primarily red algae. A. triostegus showed greater variability between sites in diet composition than A. nigrofuscus, and when grouped at the site, shore, or species level, A. triostegus tended to have greater diet overlap among individuals. Conversely, A. nigrofuscus exhibited greater variation in diet among individuals, with less diet variability between sites. Grazing surgeonfishes such as these are critical components of existing and future herbivore management plans, making their diet breadth and consequent vulnerability to habitat loss or disturbance of great interest to resource managers.
