Fewer obligate coral-dependent fishes associated with corals covered by coral-killing sponge Terpios hoshinota

Abstract

While outbreaks of the coral-killing sponge Terpios hoshinota are now being increasingly reported across the Western Pacific and Indian Oceans, no studies have yet investigated the effects of T. hoshinota on coral reef fishes. We compared the abundance, species richness, and community composition of fishes across three habitat types (live corals, Terpios-covered corals, and dead corals) at Lanyu and Lyudao, Taiwan. The abundance and composition of different fish species groups (cryptic, resident, or transient) were also examined between habitat types to assess potential variation depending on fish–coral interactions. Obligate coral-dependent fishes (corallivores and coral-dwellers) were lastly examined between habitat types due to their susceptibility to reductions in live coral cover. The presence of T. hoshinota had limited effects on the overall fish community, as well as within fish species groups, with many species displaying limited or no preference between habitat types. On the contrary, obligate coral-dependent fishes were almost twice as likely to occur, and up to five times more abundant on live corals compared to Terpios-covered corals. These findings suggest that although T. hoshinota appears to have limited effects on the majority of fishes at the individual colony scale, mass outbreaks could potentially cause affected fish communities to become dominated by habitat generalists, at the expense of obligate coral-dependent species. Further research should therefore investigate community-level responses to large outbreaks of T. hoshinota.