For human populations, fish constitute a major source of long chain n-3 polyunsaturated fatty acids (n-3 LC PUFA), commonly named omega 3, necessary to maintain vital functions. Exploited small pelagic fishes (SPF), mostly from Eastern Boundary Upwelling Systems (EBUS), are major contributors to human n-3 LC PUFA direct consumption and use. Ongoing climate change combined with increasing human population currently lead to a clear warning that n-3 LC PUFA supply may become insufficient by 2040. Assessing the impact of environmental changes on n-3 LC PUFA accumulation by SPF and their consequences on SPF populations is becoming urgent to maintain ecosystem functioning and omega 3 supply to humans. This very fundamental scientific question burdened with ecological and socio-economic issues and public health concerns has barely been considered at a worldwide scale yet. To pioneer this challenging question, this project will first focus on the Bay of Biscay (BoB) as a reference study site to develop ground-breaking research methodology, which will then be disseminated to the four EBUS (Humboldt, Benguela, Canary & California). In addition, effect of fish production methods (e.g. fishing gears, season, tidal duration, conservation on board, landing location, processing) on n-3 LC PUFA fish content, as well as fishermen and consumers perceptions on the relationship between global changes and fish n-3 LC PUFA consumption will certainly benefit to sustainable fisheries governance and n-3 LC PUFA supply for humans. The project will benefit from a unique interdisciplinary panel of experts of BoB, and disciplinary experts of the four EBUS, gathered from the different ISblue units for this frontier project, as well as existing national and international collaborations. We will combine in situ observations, experiments, modelling, economics, and sociologic analyses, to evaluate (1) the spatial-temporal variability of n-3 LC PUFA content in SPF, (2) the influence of n-3 LC PUFA trophic availability on SPF physiology and behavior, and (3) its impacts at population scale and the potential future changes in n-3 LC PUFA supplies, (4) the effects of fishing production methods on fish quality in terms of n-3 LC PUFA, and (5) fishermen/consumer representations, and the acceptable alternative sources of n-3 LC PUFA for consumers.