Disease outbreaks in aquaculture cause massive welfare harm to affected fish and require treatments that themselves have welfare costs, making disease prevention the primary welfare strategy in intensive fish farming.
Disease in aquaculture causes fish to experience the pain of physical lesions, systemic infection, and deteriorating vital functions often without timely intervention. Because monitoring individual fish health is practically impossible at scale, disease is often detected only when mortality rates rise. Preventive approaches including vaccination, genetic selection for disease resistance, and robust biosecurity significantly reduce disease-related welfare harm. The trend toward reduced antibiotic use is positive from a public health perspective but requires disease control to be achieved through other means, including improved welfare standards that reduce stress-induced susceptibility.