PhD defence: Miiro Ilmari Virtanen

Thesis title​​​:

Internal tagging in Atlantic salmon (Salmo salar L.): A study of welfare, wounds, and stress

Trial lecture topic:

Can fish feel pain?

Evaluation Committee:

• Associate Professor Katja Anttila, University of Turku, Finland
• Researcher Henrik Sundh, University of Gothenburg, Sweden
• Associate Professor Torstein Kristensen, Nord University

Supervisory Committee:

• Main supervisor: Associate Professor Martin Haugmo Iversen, Nord University
• Co-supervisor: Professor Monica Fengsrud Brinchmann, Nord University

Thesis summary:

While fish might be in the dark when it comes to expressing their own well-being, with the use of real-time smart tags, they are now ready to spill the beans, creating a path to improve fish welfare in aquaculture. But wait, not so fast! We must pause and ponder whether implanting these smart tags inadvertently introduces stress, altering their behaviour so that measurements no longer reflect the broader population they are meant to represent. This thesis explores the physical, physiological, and transcriptomic responses to surgical tagging in stress-free and stressful environments. The findings suggest that tagging, in general, does not trigger long-term stress responses and that wound healing occurs. However, when a daily stressor is introduced, dysregulation of the stress axis is observed, profoundly affecting stress indicators, wound healing, and skin health. Therefore, it is important to consider when and how to tag fish since aquaculture facilities are not immune to stressful conditions.