Sediment processing by the surgeonfish Ctenochaetus striatus at Moorea, French Polynesia

The sediment-feeding surgeonfish Ctenochaetus striatus was found to reduce the sizes of ingested carbonaceous particles. The mean sizes of particles in stomach samples of the surgeonfish were smaller than those from areas where the fish were observed feeding. The particle sizes in the rectal contents of the fish were smaller than those in the stomach samples. The sediment-feeding activities of this and related surgeonfishes are likely to have a local impact on the particle-size distributions of sediments in reef and lagoon habitats. The assimilation efficiencies of the fish were estimated by the ash-ratio method to be 20% for total organic matter and 37% for nitrogen.