Refining the invertivore: diversity and specialisation in fish predation on coral reef crustaceans

Crustaceans are one of the most influential groups in aquatic trophic networks by providing a major connection between primary production and higher consumers. Although coral reefs support a high diversity and abundance of crustaceans and crustacean predators, their trophic interrelationships remain unclear. Using predator gut content analyses, we investigated trophic relationships between Crustacea and adult fishes of the family Labridae, which are one of the most abundant and diverse families of marine crustacean predators. Crustaceans were present within the guts of 93 % of the 30 wrasse genera investigated. We found a distinct division between micro- and macro-crustacean predators: wrasses <80 mm standard length (SL) were predominantly micro-crustacean feeders, while wrasses >90 mm SL displayed a predominantly macro-Crustacea diet. Notably, micro-crustacean predators tended to specialise on certain crustacean taxa, whereas macro-crustacean predators consumed mostly brachyurans. Our findings highlight complex patterns of feeding diversity within crustacean predators that prompt a more nuanced approach to defining the role of crustacean-feeding fishes in coral reef trophodynamics.