Restocking initiatives have the potential to help conserve populations of threatened species, and there is a growing interest in applying this approach to marine fish. Sciaena umbra and Dentex dentex are two coastal fish species that inhabit the Mediterranean Sea and are categorized as ‘Vulnerable’ according to the IUCN Red List. This study investigated the performance of S. umbra and D. dentex hatchery-reared juveniles feeding on live prey. We evaluated whether 6 days of training and body size had an impact on feeding performance and behaviour. In both species, we found that training had a positive effect on fish feeding performance by (1) significantly increasing mean number of prey eaten, (2) decreasing the latencies before first attack and first ingestion and (3) increasing attack efficiency. In addition, there was a significant increase in the number of S. umbra individuals that ingested at least one prey item over the 6 training days. The percentage of fish that ingested at least one prey item did not, however, increase significantly for D. dentex individuals over this period; instead juveniles either (1) attempted to eat novel prey, succeeded and displayed an improvement of their feeding efficiency through training, or (2) did not forage or eat over the 6 training days. The high number of individuals exhibiting the second response could be linked to several factors, including fear, personality or the type of prey used in this study. In S. umbra, individuals from the [50–60[ mm total length size class outperformed other size classes. Our findings highlight differences in feeding behaviour between the two species and the positive impacts of training on feeding performance. Our results should be taken into account when developing release protocols for potential restocking programmes.