Stocking density is one of the most important variables in aquaculture welfare, with overcrowding causing chronic stress, injury, and disease that compromise fish lives.
Fish in overcrowded aquaculture systems experience chronic stress from competition, reduced water quality, limited behavioral space, and elevated disease pressure. Physiological stress markers including cortisol remain chronically elevated rather than returning to baseline after acute stressors. This chronic stress state suppresses immune function and increases disease susceptibility, requiring more medication and producing fish with compromised welfare. The economics of density reduction are challenging for producers, but certification systems and consumer demand for better welfare are creating pathways for financially viable density reduction.