The effect of coral reef degradation on the trophic structure of reef fishes from Bahia Culebra, North Pacific coast of Costa Rica

Fishes play numerous key ecological roles that are critical for maintaining the structure and function of coral reefs. Natural and anthropogenic disturbances can produce structural changes in coral reef habitats, which consequently may affect the trophic structure and dynamics of reef fish assemblages. Therefore, changes in the coral cover of coral reefs, caused by disturbance events can impact the abundance of reef fishes. This study determined the effect of habitat degradation on the trophic structure of coral reef fishes from Bahia Culebra, a bay located in the north Pacific of Costa Rica. We examined whether spatial and temporal changes in live coral cover (LCC) and substrate type between two periods (1995-1996 and 2014-2016) influenced the trophic structure of coral reef fishes. While planktivorous fishes maintained similar abundances between periods, omnivorous fishes (mainly facultative corallivores) were less abundant in sites with low LCC. There was a decline in abundance of mesopredators (e.g. sharks, groupers, snappers), probably because of both shelter loss and overfishing. Macroalgae feeders, herbivores-detritivores and invertivores showed high abundance in disturbed coral reefs, which could be related to predator decline or to increased algal resource abundance. Despite high abundance of herbivorous fishes, high macroalgae coverage persisted during the 2014-2016 period. The results from this study suggest that degradation of coral reef habitats from Bahia Culebra have affected the trophic structure of reef fish assemblages, and potentially the functioning of this coastal ecosystem.