Advancing the Contemporary Understanding of Ecological Roles of Sharks on Coral Reefs

Abstract

Coral reefs are one of the most biologically diverse and productive ecosystems globally and among the most vulnerable to environmental change. As common predators on reefs, sharks have often been perceived to play a critical role in the dynamics of coral reef ecosystems. Yet, there is relatively little evidence to support this idea across all but a limited set of species and contexts. Research on the ecological roles of reef sharks has been complicated by logistical challenges in collecting shark-related data compounded by widespread declines in shark populations and reef state due to anthropogenic stressors. The rapid decline of reef environments has necessitated management strategies that prioritize ecosystem function to protect key processes and services that reefs provide. However, an improved understanding of ecological roles is essential for uncovering when, where, and how sharks contribute to the function of coral reef ecosystems. This thesis aims to advance the contemporary understanding of the ecological roles of sharks on coral reefs to support effective management of coral reef ecosystem function. First, I present a standardized framework for determining the ecological roles of reef sharks to provide researchers with a detailed and directed approach to explore the mechanisms and patterns that comprise roles and address persistent gaps in knowledge. Next, I explore the complex biological and socio-economic relationships that dictate the current abundance of sharks on coral reefs and quantify the potential of management interventions for mitigating population declines. I then illustrate the importance of ecological context through an examination of intraspecific variation in the movement ecology of reef shark populations across various locations. Lastly, I introduce an emerging causal inference framework tailored to aquatic animal telemetry data to advance methodological approaches for drawing causal conclusions from complex observational data. Overall, this thesis demonstrates how various challenges associated with research on the ecological roles of reef sharks have shaped our current understanding and provides a path forward for optimizing future research to build on existing knowledge. Ultimately, an improved understanding of the ecological roles of sharks on coral reefs is fundamental to modern management strategies that target ecosystem function.