Tropical pelagic biodiversity plays an essential role for the food security and incomes of many coastal developing countries, thus calling for its sustainable use. It is currently subject to major stressors from human activities and climate change. Due to its sparseness, remoteness and vastness, the open ocean is difficult to access and monitor. As a consequence, the diversity trends and status of pelagic species still remain poorly assessed. The project aims at filling this knowledge gap, by developing monitoring platforms to observe the open ocean and its biodiversity in collaboration with fishers. At the core of the project is the fact that thousands of platforms already exist in the open ocean and are regularly maintained by fishers: the so-called Fish Aggregating Devices (FADs). FADs are artificial buoys or rafts deployed offshore by fishers to increase their chances of finding fish. They exploit the behavior of many tropical species, which associate and form multi-specific aggregations around floating objects. The project builds upon this concept and aims at using FADs as scientific platforms to access the open ocean and monitor its pelagic biodiversity. The project focuses on three main study areas located in the Indian ocean: Mayotte (French overseas department), the Maldives and Indonesia. The methodology employed relies on the combination of innovative monitoring techniques conducted at FADs, ranging from molecular ecology (eDNA, metabarcoding), underwater acoustics (echosounders and bioacoustics) as well as underwater videos, supported by the use of artificial intelligence for species identification. The project also employs a citizen-science approach that builds upon the traditional and ecological knowledge of fishers, empowering fishers to promote community-based ocean monitoring and ocean sustainability. Furthermore, more conventional existing data, such as catch data, is considered and harmonized with the new data collected to produce relevant biodiversity indicators. The knowledge on pelagic biodiversity produced by the project’s interdisciplinary scientific team is the platform on which all knowledge-holders exchange, learn and create close connections to promote the long-term and multi-faceted use of such monitoring schemes. Because the pelagic resource is, by nature, distributed over wide ranges going beyond national borders, the project has an intrinsic transnational dimension. It is relevant for policy-making and society, since it aims at providing new knowledge for the sustainable use of pelagic biodiversity. Given the importance of pelagic resources for food security, their sustainable use is a global societal challenge in line with the United Nations Agenda for Sustainable Development (Goal 14). The results of the project can support several end-users, from fishers (by improving the sustainability of their fishing practices) to international policy makers, such as the tuna Regional Fisheries Management Organizations.