Spatial distributions and foraging substrates of 11 surgeonfish species (family Acanthuridae) in an Okinawan coral reef

Abstract

Surgeonfishes (family Acanthuridae) are a main fish group in coral reefs. This study aimed to examine the species-specific and size-related spatial distribution, and foraging substrates of 11 surgeonfish species in relation to topographical features and substrate diversity. Six species (Ctenochaetus striatus, Acanthurus nigrofuscus, A. lineatus, A. japonicus, Naso lituratus, and Zebrasoma scopas) showed a greater density in the outer reefs with a higher coverage of rock. The former five species showed a significant positive utilization of rock as foraging substrate, whereas Z. scopas positively utilized dead corals and rock. For A. dussumieri and N. unicornis, greater densities of smaller-sized individuals were found in the inner reefs with higher coverage of coral rubble and sand, whereas larger-sized individuals were found in the outer reefs with a higher coverage of rock. Naso unicornis showed a significantly positive utilization of rock as foraging substrate. Ctenochaetus binotatus tended to show greater density in the outer reefs and a significant positive utilization of rock as a foraging substrate. Acanthurus nigricauda tended to show greater density in the inner reefs and a significant positive utilization of sand as foraging substrate. Zebrasoma velifer showed greater density of smaller-sized individuals in the inner reefs with higher coverage of live corals and dead corals, whereas larger-sized individuals tended to be greater in the outer reefs with a higher coverage of rock. Zebrasoma velifer showed a significant positive utilization of dead corals as foraging substrate. These results indicated that non-coralline substrates are the main indicator for maintaining surgeonfish species diversity.