Epsilon Archive for Student Projects

Abstract

Understanding the movement and migratory patterns of reef fish is essential for effective fisheries management, particularly in regions intrinsically reliant on marine resources, such as Rangiroa Atoll in French Polynesia. The longnose emperor (Lethrinus olivaceus) is a keystone species in the local fishery, yet its spatial ecology and the influence of environmental factors, such as the lunar cycle, remain underexplored. This study aimed to address these knowledge gaps by investigating the migration patterns, spatial utilization and ecological behaviours of longnose emperors within the Rangiroa lagoon, while also integrating local ecological knowledge to support future sustainable resource management efforts. To this aim, acoustic telemetry was employed to track the movements of 75 individuals across a network of 80 receivers deployed throughout the Rangiroa lagoon and its two major passes (i.e. Tiputa pass and Avatoru pass), from September 2023 to May 2024. Complementary interviews with local fishers provided a holistic understanding of the species’ behaviour. The results revealed that longnose emperors undertook distinct movement patterns, with longnose emperors exhibiting site fidelity to specific areas, such as the lagoon sides of Avatoru and Tiputa passes, and in the regulated fishing zone (ZPR). Movements were markedly influenced by lunar cycles, with fish aggregating near the passes during new moon phases, highlighting a predictable pattern that increases their vulnerability to fishing. Additionally, local ecological knowledge aligned with our findings, fishers reported similar spatiotemporal patterns, observing longnose emperors migrating and aggregating near passes and shorelines during darker lunar phases. The study underscores the need for adaptive management strategies that consider these distinct, lunar-driven movements of Rangiroa’s longnose emperor, and integrate both scientific data and local knowledge to ensure the sustainability of this important fishery resource.