Aluminium in acidic river water causes mortality of farmed Atlantic Salmon (Salmo salar L.) in Norwegian fjords

Acute mortality of Atlantic salmon has been described from fjord-based fish farms in Western Norway. Mortality is often related to snowmelt and heavy rainfall in the catchment areas during the winter. Increased freshwater runoff reduces the surface water salinity from >20 to 200 g g-1 dry weight). The increases in gill Al were related to increased discharge episodes where acidic, Al-rich freshwater elevated the surface water concentrations of Al from 70 g Al l-1. Increased mobility of reactive Al (Ala) and increased Al accumulation on gills during flood episodes was the probable cause of the massive salmon mortality