In vertebrates, taste provides critical information about the quality and nature of nutrients, leading to specific eating responses (consumption or avoidance), fundamental to their growth and survival. Taste perception is one of the first sensing system involved in oro-sensory detection of nutrients that play a key role in the regulation of feeding behaviour. Previous studies revealed that the concomitant replacement of traditional ingredients of aquafeed, fish meal and fish oil by plant ingredients from first feeding of rainbow trout (RT, Oncorhynchus mykiss) led to a reduction of growth and survival rates (Lazzarotto et al., 2018), mainly related to altered feeding behavior. In fishes, the genetic basis underlying the formation of food habits by the oro-sensing system and its involvement in the regulation of feeding behaviour is largely unknown. Therefore, this study aimed to decipher the involvement of gustatory component in the regulation of food intake of RT fed from the first feeding with plant-based diet. A feeding trial was conducted for 8 months from the first feeding, with a control diet or a plant-based diet lacking marine ingredients. Overall, the plant-based diet altered growth performance of RT early, which could be related to an early and sustained decrease of feed intake as compared to control diet. Mechanistically, taste receptors were mainly expressed (gene expression) in taste organs (mainly in tongue) and regulated by diet, which indicated the function of the taste receptors. Some taste receptors for fatty acids (such as the ffar receptor) were differentially modulated in tongue and brain of RT by the control diet vs plant-based diet as well as the regulation of pathways involved in nutrients detection (such as calcium or monoaminergic pathways). Overall findings show that RT displayed the fundamental mechanisms for oro-gustatory perception of nutrients related to different diet composition. The data obtained also indicated taste receptors and actors of pathways could plays an important role in the regulation of food intake, linked to the alteration of growth performance in RT fed plant-based diet.