This preliminary study assessed genotype x diet interaction in late growth of European sea bass (Dicentrarchus labrax) fed with either a fish meal (FM)- or a fish oil (FO)-based diet (M) or an all-plant-based (PB) diet. A total of 550 fish from 224 families were reared together and tagged. DNA was sampled and microsatellites were used to assign parentage. When fish weight was 192 +/- 54 g, two tanks were fed with M (FM: 100%; FO: 100%) and two others with PB (FM: 0% and FO: 0%). Body weight (BW), fork length (FL) and fillet lipid content (CorrFat) were analysed with a linear model and with REML methodology. We observed no significant differences between groups, but a slightly lower (P=0.03) daily growth coefficient in sea bass fed PB than in those fed M. Heritability estimates of BW differed significantly from zero (PB: 0.37 +/- 0.18; M: 0.47 +/- 0.24). Sire x diet interactions were significant and genetic correlations ranged between 0.51 and 0.87, showing genotype x diet interaction for BW and CorrFat. For the first time, genetic parameters in the context of total replacement of marine fishery by-products were estimated in European sea bass, showing re-ranking of family performances with extremely contrasted diets.