Biosecurity — preventing and controlling disease — is central to aquaculture welfare. Disease outbreaks cause mass suffering among farmed fish and shellfish, and the methods used to control disease have their own welfare implications.
Disease in aquaculture is simultaneously a welfare emergency and an economic one. Fish suffering from viral hemorrhagic septicemia, bacterial infections, or parasitic infestations experience significant distress before death. The welfare-protective response requires integrated approaches: prevention through biosecurity, rapid diagnosis and humane treatment when disease occurs, and slaughter-before-suffering protocols when mass mortality is inevitable. Antibiotic resistance is a growing concern — overuse of antibiotics in aquaculture creates resistant bacteria that threaten both animal and human health. Investment in vaccines, probiotics, selective breeding for disease resistance, and closed containment systems serves both welfare and long-term sustainability.