Bumphead parrotfish

Photo: Mark Rosenstein · CC BY-NC

The world's largest parrotfish, bumpheads move in schools of dozens that headbutt and bite chunks out of coral skeleton, producing prodigious quantities of white sand. Their bioerosion is ecologically essential: it recycles nutrients locked in dead coral and creates sandy substrate for other organisms. Schools are most spectacular at dawn, when the fish emerge from overnight resting sites and begin feeding along the wall crest.