European sea bass in cage aquaculture are aggressive, hierarchical fish whose welfare is significantly affected by stocking density, feeding regime and group composition.
Sea bass establish dominance hierarchies in which subordinate individuals receive less feed, experience higher cortisol levels and show suppressed growth. In high-density systems, subordinates cannot escape dominant conspecifics, leading to chronic stress. Size grading to create uniform groups reduces aggression frequency. Ensuring adequate feed distribution throughout the cage, rather than at single points, reduces competition-related welfare impacts.