Changes in water quality during commercial freshwater bathing of Atlantic salmon (Salmo salar) in Tasmania - implications for treatment of Amoebic Gill Disease

Changes in water quality of commercial freshwater baths used to treat Atlantic salmon (Salmo salar) with Amoebic Gill Disease (AGD) were examined at three aquaculture sites. The bathing time ranged from 2.4 to 3.7 hours. Water pH was significantly greater before than after the bathing. Farm site had a statistically significant effect on water pH changes. Ammonia values increased slightly after bathing from 0 to 0.25 mg/l at two of the sites, while nitrate and nitrite levels remained undetectable. Sodium, potassium and chloride levels differed between sites and baths. The magnitude of the changes was minimal indicating the ionic balance of the fish is not adversely affected by the freshwater bathing.