About This Project

In French Polynesia, coral reef fisheries are being revitalized using the traditional practice of Rāhui. A Rāhui is a temporary no-take marine reserve to rebuild fish abundance. Decisions about safe return to fishing require reliable monitoring. This project uses drone-based mapping to obtain geospatial data of the Rāhui, which will form the basis of habitat-stratified monitoring. We expect habitat stratification to increase reliability of fish counts and to effectively inform Rāhui management.

Ask the Scientists

What is the context of this research?

Tautira’s Rāhui, located on Tahiti’s large coral reefs in French Polynesia, exemplifies community-based marine management. Established in 2018 by Taiarapu-Est’s municipality, it remains the only actively managed Rāhui for fisheries production. In partnership with the Rāhui Center, local authorities and communities collaborate to co-design Marine Managed Areas and conduct scientific studies.

Since 2021, reef fish monitoring has faced challenges due to limited resources and imprecise spatial data. Tautira’s reef habitats require detailed mapping to ensure effective management. Drone-based mapping offers an innovative, cost-effective solution, integrating with Geographic Information Systems (GIS) to create precise geospatial habitat layers. These insights will improve survey reliability, optimize fish counts, ensure more reliable and cost-efficient monitoring, foster community dialogue and guide rotational Rāhui openings for sustainable fishing.

What is the significance of this project?

This project aims at enhancing decision-making while complementing community-led traditional management practices. The success of the Rāhui depends on precise and unbiased observations of fish populations and their potential recovery. While preliminary surveys of the Rāhui demonstrate the feasibility of underwater visual fish counts, this project will provide crucial geospatial measurements necessary for survey refinement, including spatial stratification, and habitat characterization. In turn, this project aims to achieve better conservation outcomes by ensuring that surveys are statistically robust, efficient in required field sampling effort, and directly relevant to decision-making by Tautira’s Rāhui Management Committee. Broadly speaking, mapping the reserve will leverage several scientific endeavors, such as the robust design of reef fish surveys, control for habitat and substrate type, and feed long-term discussions on improving the design of Rāhui together with stakeholders.

What are the goals of the project?

1. Conduct mapping of reef habitats within the Rāhui marine reserve: use drone-based imagery to create detailed maps of the coral reef habitats within the closed reserve area, identifying key features and habitat types. Generate high-resolution GIS layers serving as a foundation for survey design, and enable a clearer understanding of the relationship between reef fish populations and their habitats.

2. Develop an improved sampling design for underwater visual fish surveys: utilize mapping data to optimize reef fish survey designs, consisting of design-based stratified-random sampling and optimization of strata-level sampling effort allocation.

3. Foster engagement and discussions on the effectiveness of Rāhui: learn lessons on the impact of the reserve’s characteristics, such as its extent, its substrate types, favorable habitats, among others, and bring those learnings to the community leaders to discuss the future of this rāhui and others around French Polynesia.