Winter ulcers in salmon during their second autumn and winter/early spring at sea lead to reduced welfare, losses, and downgrading in Norwegian salmon farming. The bacteria causing winter ulcers thrive at low seawater temperatures, and the risk of ulcer development increases when fish are handled at low or decreasing temperatures.
The increased use of non-medicinal treatments for salmon lice (e.g., freshwater, mechanical, or thermal treatment) has led to more frequent handling. In particular, the crowding process prior to treatment has been highlighted as critical for how fish are affected by handling.
In the ReduSår project, we aim to generate knowledge on which measures may be relevant to implement during crowding to reduce the risk of ulcer development after handling, and what decision-making basis should underpin the choice of extraordinary measures. In the project, we have:
- Collected best practice recommendations from the industry.
- Conducted a mesoscale trial to map the effects of sedation and crowding intensity during crowding on stress and immune responses, skin health, and ulcer development.
- Studied potential indicators for ulcer risk and early warning of ulcer outbreaks.
Header image: Mette Remen/SINTEF.