Effects of Cannibalism, Feeding on Artificial Feed, and Mixed Feeding on Growth Performance, Physiological Metabolism, and Immune Gene Expression in Juvenile <em>Lates calcarifer</em>

To optimize juvenile barramundi (Lates calcarifer) feeding strategies, this study compared cannibalism (CB), formulated feed (FF), and mixed feed (MIX: formulated + biological feed) on growth, physiology, and immune-related gene expression. 36-day-old juveniles (initial body weight) were randomized into 3 groups (1 Lates calcarifer was placed in each tank, with 15 replicates in each group.) for a 20-day trial. Growth performance: MIX group showed significantly higher weight gain rate (862.31 ± 346.66) and specific growth rate (93.2 ± 42.48) than FF and CB groups (P &lt; 0.05); CB group outperformed FF (P&lt; 0.05). Physiology: MIX had the highest alkaline phosphatase (AKP) and pyruvate kinase (PK) activities (P &lt; 0.05), and significantly elevated alanine aminotransferase (ALT) activity, lipid peroxide (LPO) content, but the lowest catalase (CAT) activity (P &lt; 0.05). Gene expression: CB group had the highest lysosomal protease (cts1a) and glycolytic gene (eno3) levels (P &lt; 0.05); FF group showed higher heat-shock protein 90(hsp90) and pro-inflammatory cytokine (IL1β) expression (P &lt; 0.05). FF exhibited the highest SOD activity and IL1β levels (P &lt; 0.05), indicating strong antioxidant. Conclusion: MIX promotes growth but risks liver damage/oxidative stress; CB serves as emergency nutrition but requires management to avoid; FF exhibits significant antioxidant advantages despite poor growth performance. "Mixed feeding + immune enhancers" is recommended for industrial seedling production to balance growth and health.