Rapid reduction in biodiversity and abundance of Caribbean coral reef fishes at cleaning stations following removal of coral-dwelling cleaner gobies.

Understanding the dynamics of species distribution and abundance, as well as interactions with the biotic environment, is a fundamental goal of ecology. While factors such as food availability, predation, mating, and habitat use have been extensively studied, symbioses, such as parasitism and mutualism, are also crucial drivers of community structure and ecosystem function. A prominent example of this in coral reef environments is cleaning symbiosis, where small fishes or shrimps remove parasites and tissue from larger fishes (clients). In the tropical Atlantic, where Elacatinus cleaner gobies are the dominant cleaner fish, large-scale empirical data on their effects on the distribution, abundance, and diversity of clients are lacking. Thus, how Elacatinus cleaner gobies affect coral reef community structure remains unresolved. This study investigated the impact of cleaner gobies (Elacatinus evelynae) on the spatiotemporal dynamics of mobile clients. We show that biodiversity at locations where cleaner gobies had been experimentally removed was reduced by 23%. Additionally, cleaning stations with cleaner gobies had 1.85 times the number of visits by client fish than cleaning stations where the goby was removed (n = 3,673), and that this effect was apparent within only 10 days. Following cleaner goby removal, client fish visited goby-present cleaning stations more than removal stations, with visitation rates 4.04, 1.85, and 1.97 times higher in Surveys 1, 2, and 3, respectively. Furthermore, the proportion of cleaning stations visited by clients, including goby-present stations, shifted shortly after goby removals. These findings show that cleaner gobies can be important contributors to coral reef community structure by altering activity and distribution of other fishes.