Foraging behavior and short-term response to mass coral bleaching by the facultative corallivorous pufferfish Arothron nigropunctatus in Okinawa, western Pacific

Arothron pufferfishes (Tetraodontidae) are recognized as major skeletal-feeding corallivores. However, quantitative field observations evaluating the ecological impact of coral feeding remain scarce. Furthermore, how coral feeding by Arothron pufferfishes changes in response to mass coral bleaching remains poorly understood. Here, we investigated the foraging ecology of the blackspotted pufferfish, Arothron nigropunctatus , one of the most common pufferfish species on coral reefs in the western Pacific, including Okinawa, Japan. Our field observations conducted from 2023 to 2025 on a fringing reef at Sesoko Island, Okinawa, showed that A. nigropunctatus fed mainly on Acropora and Porites corals, but also consumed a variety of other food resources, including other scleractinian corals, the epilithic algal matrix (EAM), sand-buried benthic prey, and sponges. After the 2024 mass coral bleaching event, a drastic shift in feeding behavior was observed in the pufferfish, with a sharp decline in the consumption of Acropora and sand-buried benthic prey and a concurrent increase in the consumption of EAM and other corals. The EAM contained substantial sediment loads, and A. nigropunctatus was observed feeding on it while expelling sediment from the mouth. Predation on the coral-killing sponge Chalinula nematifera by the pufferfish was also observed after the coral bleaching. These results suggest that A. nigropunctatus is a facultative corallivore with flexible foraging responses to benthic food resources under disturbed reef conditions. By not only increasing feeding on algae but also removing sediment together with EAM, Arothron nigropunctatus may have a previously overlooked functional role in post-disturbance reef recovery.