UC San Diego

Coral reefs, and particularly the study of coral reef fishes, have provided fundamental contributions to our understanding of community ecology in part due to their spectacular diversity of life. This dissertation seeks to evaluate facets of the community ecology of fish communities at reefs in the south and central Pacific Ocean via a variety of classical and new approaches, including traditional visual surveys and new techniques in genetics. Collectively, the results of my dissertation address outstanding questions regarding the communities of fishes on coral reefs at islands and atolls in the south and central Pacific, including both well-studied inhabited islands with intimate associations between humans and environments and others from remote environments that have seen only sporadic human visitation and presence. I begin with an investigation of a potential stabilizing mechanism of coexistence through the application of metagenomics to assess dietary niche-partitioning in a guild of hawkfish from remote reefs in the central equatorial Pacific. We observe previously unidentified relationships in this cryptic species complex at its proposed center of distribution and separate clustering of species for both the microbial community of the gut and presumed prey sequences. I next calculate length–weight relationships for abundant coral reef fish species from eight different islands in French Polynesia. These region-specific biological parameters are important for assessing accurate metrics of biomass for coral reef fish communities from underwater visual surveys. I focus on members of the community that are often overlooked and understudied in such contexts, including species of importance for the aquarium trade. I then assess temporal patterns in trophic groups of coral reef fishes via remote video surveys on forereefs of Moorea, French Polynesia. I conclude by investigating the “paradox of planktivores”—that is, the substantial number of co-occurring reef fishes that are presumably relying on similar resources. I use metagenomic sequencing and underwater visual surveys to assess the evidence for niche-partitioning and changes in observed abundance through time that could indicate coexistence in a guild of closely related planktivorous reef fishes.