Crowding in fish farming suppresses immune function and increases disease susceptibility, creating a direct link between welfare and fish health outcomes.
The relationship between crowding, stress, and disease in farmed fish creates one of the clearest cases for welfare-economics alignment in aquaculture. Crowded fish produce more cortisol, which suppresses their immune response, which increases disease outbreaks, which require costly treatment. Reducing crowding below disease-critical thresholds improves fish welfare, reduces disease losses, and reduces antibiotic dependency simultaneously. This triple benefit means that crowding reduction is one of the most compelling welfare arguments available in the aquaculture sector, aligning with both economic and antimicrobial stewardship goals.