Drone Diaries of The Bahamas

Many marine megafauna populations, including sea turtles, ray, and sharks, are sensitive to both local and global impacts and yet, remain relatively difficult to monitor. With funding from Save Our Seas Foundation , my collaborators and I tested the efficacy of a quadcopter drone to collect megafauna abundance data in multiple shallow-water habitats in the realistic background variation of shoreline development. We repeated drone surveys at three paired high and low human population sites. In short,  the drone imagery allowed use to monitor these species. In addition, there were also noted patterns in the occupancy of our focal species, finding higher abundances of all species in our low human population sites compared to high human population sites.

(A) is a snapshot of an eagle ray and (B) is a snapshot of a sea turtle; both are taken from our drone video surveys.

Our results highlight the ability of consumer-grade drones to accurately and efficiently estimate the abundance and distribution of large-bodied elasmobranchs and sea turtles in shallow water habitats. Further, our study supports their capability to evaluate issues related to the conservation and management of nearshore ecosystems.

Nassau Grouper and Reef Complexity Effects on Fish Community Assemblage

Coral reef ecosystems are highly diverse habitats that harbour many ecologically and economically significant species, yet they are currently under threat from multiple stressors including overexploitation of predatory fishes and habitat degradation. While these two human-driven activities occur simultaneously in nature, they are often studied independently or are limited to simplified interaction webs. Using a factorial design, we examined effects of predator presence, habitat complexity, and their interaction on patch reef fish communities in nearshore ecosystem on Great Abaco Island, The Bahamas. We manipulated the presence of Nassau groupers (Epinephelus striatus), a large-bodied reef predator that is endangered largely due to overharvest, and manipulated patch reef complexity using artificial reefs (composed of PVC and cinder blocks) to reflect either high or low complexity. To assess changes in fish community composition measured fish abundance, species richness and evenness, and characterized fish community composition. A major finding from this study was that we found reef complexity and predator presence to have a positive, additive effect on total fish abundance, likely from ample refugia availability and non-consumptive predator effects. In the context of coral reef conservation, our study suggests that to maintain a healthy, productive reef system, we need to manage stressors that affect both the bottom and top of reef food webs.

This photo demonstrates the stark contrast in fish abundance between two reef treatments, no predator presence, low reef complexity (left) and predator presence, high reef complexity (right).