The whitefish ( Coregonus lavaretus) is a core exploited species in numerous fisheries and the invasion of the European catfish ( Silurus glanis) in peri-Alpine lakes may represent an emergent threat to this salmonid. We aimed to assess the whitefish vulnerability to catfish in a French peri-Alpine lake (Lake Bourget) by combining diet analyses (metabarcoding), trophic link inferences from an allometric niche model (aNM), and the development of a predation risk metric derived from species depth matching and catfish energy demand. Whitefish DNA was found in 7% of catfish intestines, indicating a low but effective consumption. The aNM suggested that catfish (considering the current population size structure) may predate all whitefish life stages; though young-of-the-year (0 + , 5–20 cm) may be the most exposed to predation. 0 + had higher depth matching with catfish than other life stages, especially in summer when the catfish exhibit their highest energy demand, leading to an overall higher predation risk. Our results highlighted the effective consumption of C. lavaretus by S. glanis and its time and age-varying vulnerability, suggesting that S. glanis may represent a new growing threat to this salmonid in a global change context.