In Europe, natural and man-engineered aquatic ecosystems undergo multiple anthropogenic pressures that challenge their good functioning and/or productivity. Most of ecotoxicological studies have been focusing on single stressor whereas the combined effects of multiple stressors may not simply be additive, but antagonistic or synergistic. Therefore, the FishStress project addresses the question of multiple stressors in fish with a focus on nutrient/nutritional stress, chemical stress induced by metals and thermal stress since these are the drivers of ecosystem health and aquaculture productivity. The main objectives are to determine the effect of nutritional quality, tissue lipid status and selected lipids on the response of fish cells, tissues and individuals to metal (Cd and MeHg) and thermal stress across different levels of biological organisation and to verify to what extent multiple stress effects occurring at higher levels of organisation can be predicted/explained based on observations of effects occurring at lower levels. During the 2 years of the project, different experiments on fish (zebra fish and rainbow trout) will be conducted. On one hand the influence of different FA profiles of fish on their further sensitivity to metal exposure and/or thermal stress will be studied. On the other hand, the influence of metal exposure or thermal stress during fish maturation on the assimilation of different FA will be investigated. The investigation will be conducted at different levels of biological organisation (from cells to population) and will involve molecular biological measurements (e.g. genomic studies, antioxidant enzymes activities) as well as fitness' indicators (e.g. growth, reproduction). Thanks to this approach, the FishStress project will provide a solid framework to better understand multiple stressors on fish and to link the biological effects across biological levels of organisation.