Energy costs and benefits of locomotion and feeding in site-attached damselfish.

Energetic cost-benefit balance provides valuable information on the environmental tolerances and distributions of animals. In aquatic environments, flow is a fundamental factor owing to its effects on locomotion and foraging. Energetic trade-offs have been well studied in river fishes, but remain understudied in coral reef fishes. Here, we assessed energy balance of the coral reef damselfish (Chromis viridis) by measuring its oxygen consumption and feeding rate. To accurately estimate energy costs during feeding maneuvers, oxygen consumption during feeding was estimated by the video-based dynamic body acceleration method. Our results indicate that the energetically favorable range of flow speed was 17-29 cm s-1, comprising approximately 25% of the flow speed in the fish habitat. By simulating lower prey densities, we also found critical combinations of prey density and flow speed at an energy balance. Our findings provide insights into adaptation and habitat use of site-attached fish in coral reefs.