Are soft coral habitats unfavourable? A closer look at the association between reef fishes and their habitat

The structural complexity of coral reef environments has a strong influence on the assemblage of reef-associated fishes and invertebrates. These unique ecosystems provide these reef-associated species with a broad range of potential habitats, which offer important resources such as food and shelter. The most studied habitat association on reefs is that of hard coral and fish, where hard coral cover has been found to have a large and positive influence on the assemblage of reef fishes. In contrast, soft coral has been considered poor habitat due to their chemical defences and weak body architecture. However, the empirical basis for this assumption is minimal and the ecological importance of soft corals remains controversial and unresolved. The present study closely examined fish assemblages utilising a mixed mosaic of coral reef habitats at sites ranging from hard to soft coral dominated assemblages. Fishes associated with soft coral in a variety of ways including as shelter, a source of food or a surface on which epiphytic food was sourced. Fish assemblages remained similar between soft and hard coral dominated habitats, and there was no evidence that a high percentage cover of soft coral had deleterious effects. Further, a significant increase in species richness of fishes was found with increasing soft coral cover, suggesting that the importance of soft coral habitat has been underestimated on reefs with a mosaic of different habitats. Here, we discuss the implications of these associations and suggest that soft coral provides distinct habitat for reef fishes, and future research should address their ecological importance.