Infectious salmon anemia is a viral disease causing mass mortality in farmed Atlantic salmon, with welfare implications for dying fish and biosecurity challenges for the aquaculture industry.
Salmon dying from ISA experience progressive anemia leading to weakness, surface swimming, and eventual death from cardiovascular failure. The hemorrhagic syndrome causes internal bleeding and organ damage. Mass mortalities in affected cages result in large numbers of fish suffering simultaneously without the possibility of individual veterinary care. Depopulation of infected cages via slaughter is a welfare intervention that prevents prolonged suffering of diseased fish but causes acute stress in the process. Prevention through reduced stocking density, site rotation, and biosecurity controls is the primary welfare strategy. Wild salmon infected from farm spillover face additional welfare harm without any of the veterinary oversight available in farmed contexts.