BREEDFLAT project aims to improve flatfish breeder’s performance by enhancing immune system capacity, largely affected during reproductive season, and gamete quality, by providing key-role nutrients for successful reproduction. Innovative approaches on the study of dietary effects will be attained to promote a sustainable competitive production of eggs and larvae. The consortium includes two Portuguese research teams, CCMAR (promoter) and CIIMAR, and the largest turbot producer, ACUINOVA. The Donor parties, Nord University, Akvaplan-niva, experienced in flatfish reproduction, and Sognaqua firm, will contribute with their experience in Atlantic halibut. This collaboration will enhance Portuguese centers (CCMAR, CIIMAR) performance with technology transfer from Nord (microRNAs, epigenetics), and strengthen future bilateral collaborations. The business sector (ACUINOVA) will gain from Norway experienced Aquaculture sector. The project focus in 3 important flatfish species for aquaculture diversification in Europe, Senegalese sole, turbot and Atlantic halibut, along 6 WPs. Specific breeders’ feed will be developed, considering each species’ nutritional requirements and efforts dedicated to gametogenesis. A tool-set of parameters will be developed, allowing characterization of reproductive and immune system performance. These tools will be used to evaluate the efficiency of natural feed products supplementation on the enhancement of reproduction and fish resistance. The final target is to achieve the improvement of offspring through a better nutrition to breeders. More robust juveniles will contribute to a next generation of breeders developed in captivity. These bases will provide a more sustainable Aquaculture diversification with high price commercial species, creating a benefit for fish farms and feed suppliers in Europe, reducing economic and social disparities between donor and beneficiary states.