Promoting sustainability of giant clam fishing and mariculture in atoll lagoons exposed to marine heat waves

The capacity of Pacific fisheries and mariculture to persist in the climate change context is uncertain and will depend on the ability of stakeholders to implement adaptation and resilience-building interventions that mitigate the negative impact of increased temperature. In the Tuamotu Archipelago, French Polynesia, an important population of giant clams Tridacna maxima inhabits Reao’s lagoon and provide islanders a significant income through fishing for the food market and mariculture for the aquarium trade. These activities, however, have already shown signs of vulnerability to Marine Heat Waves (MHW), which raises concern about their sustainability in face of climate change. Spatial and non-spatial management strategies have been implemented in this lagoon, but their relevance in the long term is questioned as they generate inequity issues between farmers and fishers. To help managers implementing new regulations that promote resistance and resilience of these activities to climate change, we followed an inter-disciplinary approach to (1) characterize the vulnerability (exposure and sensibility) of giant clams to temperature increase, (2) assess the potential for compliance and adaptation of fishers and farmers to new regulation measures, and (3) model the giant clam food system under various climatic and socially acceptable management scenarios. The scientific knowledge acquired from this work opens new opportunities for developing tools useful to enhance resistance and resilience of Pacific fisheries and mariculture activities to MHW. This includes: a validated remote-sensing-tool to map sea surface temperature inside atoll lagoons and identify refuge areas; the emergence of a new prototype of mariculture device that reduce the risk of giant clam bleaching by reducing light stress during MHW; and a management strategy evaluation identifying the most promising regulations among candidate scenarios that maximise resistance and resilience of the fishery-and-mariculture system to MHW.