Herbivores provide important ecological services across ecosystems where they influence productivity and plant community composition. On coral reefs, herbivorous fishes consume benthic primary producers and regulate competition between fleshy algae and reef-building corals. Many of these species are also important fishery targets yet little is known about their global status. Using a worldwide synthesis of herbivorous reef fishes we show that biomass is more than twice as high at sites not accessible to fishing relative to fished sites, independent of regional effects. Further, fishing alters community structure by disproportionately reducing biomass of larger-bodied functional groups while increasing that of smaller territorial damselfishes. This fishing down the herbivore guild likely alters the effectiveness of these fishes to regulate algal abundance on reefs. Our study reveals that herbivores are systematically affected by fishing and provides insights and baselines for herbivore assemblages which can be used for developing informed management targets globally
