The determination of exogenous enzyme contributions in live food is important in larval feeding. This study investigated the potential inhibitory effects and contributions of live foods used from 3 to 32 days after hatching (DAH) on protease activities of meagre (Argyrosomus regius) larvae (ML), using in vitro techniques. Enriched rotifer (R), Artemia nauplii (A0), and Artemia metanauplii (A1) were tested. The highest values of protease activities of ML were determined to occur at 7 DAH for the years 2013 and 2014. The lowest values were observed at 15 DAH in 2013 and at 20 DAH in 2014. Protease activities of R, A0, and A1 were 21.76 ± 0.31, 36.00 ± 1.48–29.33 ± 0.93, and 416.44 ± 19.7–403.53 ± 11.85 U/mg protein, respectively (p < 0.05). The highest inhibitions of live foods were observed at 7 DAH. This situation was related to the inadequacy of protease contributions of live feeds, despite the highest protease value of larvae at 7 DAH (p < 0.05). The positive contributions of A1 live food on the protease activities of ML were significant (p < 0.05). The inhibitory effects and positive contributions of live foods on the survival and growth rates of ML should be taken into account for future studies considering the larvae of ML and other marine fish.