Changes in reef fish assemblages following multiple bleaching events in the world’s warmest sea (Kish Island, the Persian Gulf)

Abstract

Climate change affects the ecology of reef fish through changing their habitat, community and their feeding and territorial behavior. The corals and their associated reef fish in the Persian Gulf as the world’s warmest sea suffer from the increasing frequency and severity of mass bleaching events. Yet, the effects of climate-induced coral bleaching events on reef fish in this sea are poorly understood. Using a time series fish count data, this study evaluated the response of reef fish to multiple severe coral bleaching events in Kish Island located in the central Persian Gulf. The results showed a decline in species richness and diversity of reef fish after bleaching events which reduced mean coral cover by 85% following the 2007 bleaching event and by 95% following the 2017 bleaching event. Besides a drop in the number of fish species, the total density, and density of trophic groups changed as the results of coral loss. The variation in density of different trophic groups indicated an overall increase in the abundance of benthic invertebrate feeders (21.2–136.3%), omnivores (32.4–163.4%) and plankton feeders (218.5–488%). In contrast, the abundance of coral polyp feeders (−6.9 to −50%) and piscivores (−4.9 to −38.9%) significantly decreased after bleaching events. The density of herbivorous fish significantly increased by 97.1% after the bleaching event in 2007 and decreased by 10.5% after the bleaching event in 2017. In the present study, we demonstrated how the impact of the multiple bleaching events on associated reef fish assemblages sustained for about 6 years after the disturbance. These results have significant implications for our understanding of the response of reef fish to global warming and highlight the growing concern about the future of coral reef ecosystems and their associated reef fish in the region as the warmest sea in the world.