Amoebic gill disease (AGD), caused by the amoeba Paramoeba perurans is considered a serious disease in the Norwegian salmon farming industry, and there is a great need for development of treatment strategies. Treatment with freshwater or hydrogen peroxide (H2O2) are the methods applied against AGD, and both methods have proven effect against the amoeba. Studies have shown, however, that none of the methods completely eliminate the amoeba, and in many cases the disease progresses post treatment.

Effect of different H2O2 concentrations and exposure times are studied at different water temperatures to find the H2O2 dose with the best reducing effect against AGD, while also being lenient to the fish. Another objective is to evaluate the effect of freshwater treatment against AGD at different exposure times; one-, two-, and three-hour treatment respectively. In addition, the treatment effect of brackish water with different salinities and treatment time is studied.

The effect of treatments is evaluated by following the development of AGD on the gills during a period of 21 days post-exposure, and on how the fish respond to the treatments. Experience from treatment with H2O2 and freshwater shows that AGD often develops in fish post treatment. Survivals from treatments and reproduction in survived amoebas have raised questions about resistance development against H2O2 and fresh water treatments. This project aims to study the sensitivity in a P. perurans population to H2O2- and fresh water treatment after repeated exposures.

Project manager

Sigurd Hytterød

Partners

• The Industrial and Aquatic Laboratory (ILAB)