The spatial ecology of Caribbean parrotfishes and its role in structuring benthic coral reef communities

Background/Question/Methods

Parrotfishes are functional herbivores that contribute to coral reef resilience by removing algae and promoting coral colonization. The top-down effects of parrotfishes on benthic reef communities have largely been evaluated at broad spatial scales. However, parrotfish territoriality could generate small scale heterogeneity in the benthic community by imposing spatial constraints on movement and concentrating foraging. We are investigating how territorial behavior in parrotfishes mediates their top-down effects on fringing coral reefs in Bonaire, Caribbean Netherlands. Specifically, we are testing the hypotheses that territorial behavior (1) generates temporally stable patterns of parrotfish space-use and (2) generates spatial heterogeneity in foraging that could affect small scale patterns in benthic community structure. In January and May – July 2019, we conducted GPS-tracked behavioral observations of several terminal and initial phase individuals of five parrotfish species at five reef sites, and computed home ranges for each using movement-based kernel density estimation. We then quantified home range overlap for intra and interspecific pairs and for home ranges estimated from repeated follows of the same individuals to determine the role of territoriality in driving patterns of space-use and the temporal stability of these territories. Finally, we quantified spatial patterns in parrotfish foraging at multiple spatial scales.

Results/Conclusions

Home range sizes differed significantly by species and ontogenetic phase (p < 0.001) and intraspecific home range overlap for terminal phase fishes was extremely low. Additionally, intraspecific interactions, including posturing and aggressive chases, accounted for the majority (> 70%) of interactions between terminal phase individuals in these species. Taken together, these results suggest that estimated home ranges likely correspond to defended territories. We found that the locations of these territories were fixed over short time scales (~1-5 months) as evidenced by a high degree of overlap between home ranges estimated from repeated tracks of the same terminal phase individuals. Within the context of these results, we will discuss spatial patterns of parrotfish foraging and their potential influence on benthic community structure within individual parrotfish territories and at broader reef scales.