GAIA

The capacity of Pacific fisheries to persist in the climate change context is uncertain, and will depend on their ability to implement management strategies robust to changes on the long run. As in many other semi-closed atolls in the Tuamotu Archipelago, an important population of giant clams Tridacna maxima inhabits the lagoons of Reao and Tatakoto. In these atolls where few job opportunities exist, this resource provides islanders a significant income through fishing for the food market and post larval capture and culture (PCC) for the aquarium trade. These activities, however, have already shown signs of vulnerability to high temperature, which raise concern about their sustainability in face of climate change. Reao’s and Tatakoto’s fisheries have long-term records of their activity and resource status, which provides a unique opportunity to evaluate their potential future trajectories. Spatial and non-spatial management strategies have been implemented in the two lagoons, but their relevance in the long term is questioned as they generate inequity issues between farmers and fishers. The research hypothesis is that management strategies currently implemented will have to be adjusted in the future to stay as efficient and socially sustainable as in the current conditions, because they reorganise fishing pressure on specific areas or on specific life stages that are more or less affected by temperature increase. To implement new regulation supported by scientific knowledge, however, managers lack a quantitative evaluation of the robustness of management strategies to temperature increase. GAIA is an inter-disciplinary project that will investigates the management of giant clam fisheries in semi-closed atoll lagoons, and the future of these managed fisheries exposed to climate change and notably thermal stress. The three objectives of this project are (1) to characterize the vulnerability (exposure and sensibility) of giant clams to temperature increase at Reao and Tatakoto, (2) to assess the socio-economic cost of management measures for islanders and their potential for compliance and adaptation to new regulation measures, and (3) to model the population dynamics of giant clams at the two sites, to assess the effectiveness of management strategies currently implemented, and to screen for new strategies to tackle the effects of climate change and promote sustainability of these socio-ecosystems. GAIA is structured in 7 work packages (WP). WP1 is dedicated to coordination and WP7 to dissemination. WP2 and 3 aim at characterizing the exposure and sensibility of giant clams to temperature at Reao and Tatakoto. WP4 will model lagoon hydrodynamics and T. maxima larvae dispersal at the two sites, and WP5 will identify socially sustainable management strategies. Results from WP2 to WP5 will feed the WP6, which will validate a new thermo-dependent, and spatially-explicit model of T. maxima population dynamics, and use this model to compare the effectiveness of socially sustainable management plans (currently implemented and new), and their robustness to climate change. The novelty of the GAIA project relies on its interdisciplinary nature, on the physical configuration of the study-sites which brings new challenges for hydrodynamical modelling, on new technologies that will be used, and new ideas to map fishing effort using local knowledge. This project will provide useful results for managing giant-clam-dominated atolls in Oceania, and may point out the necessity for French Polynesia to revise its long term strategy regarding the giant clam PCC activity. The project is also expected to federate research on giant clams in the Pacific, and should inflate a move toward sustainable management of fisheries in Oceania. Finally, GAIA will allow the coordinator to further develop its thematic with new approaches, extent his network of collaborations, and will be the first stone to build a more ambitious ERC project.