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 Atlan tic salmon (Salmo salar) with Amoebic Gill Disease (AGD) were examined at t hree aquaculture sites. The bathing time ranged from 2.4 to 3.7 hours. Wate r pH was significantly greater before than after the bathing. Farm site had a statistically significant effect on water pH changes. Ammonia values inc reased slightly after bathing from 0 to 0.25 mg/l at two of the sites, whil e nitrate and nitrite levels remained undetectable. Sodium, potassium and c hloride levels differed between sites and baths. The magnitude of the chang es was minimal indicating the ionic balance of the fish is not adversely af fected by the freshwater bathing.