Halftime seminar with PhD student Raneesha de Fonseka, Department of Biological and Environmental Sciences
Focus for Raneesha's PhD-project is osmoregulation in Atlantic salmon and finding reliable indicators for when the fish is ready for transition from freshwater to seawater, see below.
Opponent at the seminar is Pablo Balseiro Vigo, University of Bergen, and examiner is Staffan Andersson, Department of Biological and Environmental Sciences. Raneesha's main supervisor is Henrik Sundh with Kristina Snuttan Sundell and Lisa Jönsson Bergman as co-supervisors.
Short summary
Smoltification, is a transitional stage in which Atlantic salmon parr prepare for a life in seawater while still in freshwater. High-quality smolts- characterized by increased hypo-osmoregulatory ability, optimal growth, efficient feed conversion, and stress resilience are essential for successful aquaculture (Montgomery et al., 2025). However, poor smolt quality remains a challenge, leading to higher mortality rates, increased disease risks, and growth issues, particularly in the first months following seawater transfer. In 2023, Norwegian aquaculture reported a 4.5 % mortality rate in SW phase due to poor smolt quality (Sommerset et al., 2024). Thus, the industry seeks reliable indicators to confirm the full hypo-osmoregulatory capacity of smolts. Currently, gill Na+/K+/ATPase enzyme activity (NKA) is the primary indicator, but it does not reflect osmoregulatory changes in the kidney and intestine. Therefore, we believe that assessing synchronised NKA upregulation across key osmoregulatory organs may provide a more accurate measure of smolt readiness.