Understanding abundance, behavior, and trophic position of mesopredatory reef fish: case studies from the Western Pacific and Caribbean Oceans

Abstract

Predator – prey dynamics are fundamental drivers of population structure, diversity, and behavior of organisms in all natural ecosystems. With the reduction of apex predators from human activities in almost every ecosystem, including terrestrial and aquatic, lower trophic level predators are becoming increasingly important in the Anthropocene. Understanding the behavioral traits of mesopredators is required for a better understanding of the relationships between predation and vulnerable life history stages for prey. Coral reefs are ideal model systems to examine the relationships mesopredators have with their environment and the communities of organisms they influence. Here, I conducted two experiments investigating the behavior of mesopredator reef fish in the Indo-Pacific and Caribbean Oceans. The arc-eye hawkfish, Paracirrhites arcatus, is a common fish found in the tropical waters of the Pacific Ocean. My findings demonstrate a strong preference for the branching Scleractinian coral, Pocillopora eydouxi, by P. arcatus on the reefs around Moorea, French Polynesia. Abundance of this preferred substrate explained the density and territory size for P. arcatus. ☐ Habitat appears to be an important factor in determining behavioral characteristics of mesopredators worldwide. On the Mesoamerican Barrier Reef System, the common mesopredator Halichoeres bivittatus, the slippery dick wrasse was also influenced by habitat, most notably through diet, determined by stable isotope analysis, and density. These findings indicated that H. bivittatus individuals are site-attached, despite being found in both rubble and seagrass habitats. Findings from this study demonstrated variation in diet, not only based on fish size, but also by habitat. ☐ Understanding the behavior of these organisms in coral reef environments can better inform scientists about the ecological influence mesopredators have on population structures, particularly resulting from predation on the early life history stages of other coral reef fishes.