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Trial Lecture – time and place
See Trial Lecture.
Adjudication committee
- First opponent: Professor Holly Shiels, University of Manchester
- Second opponent: Professor Bengt Finstad, NTNU: Norwegian University of Science and Technology
- Third member and chair of the evaluation committee: Professor Shuo-Wang Qiao, University of Oslo
Chair of the Defence
Professor II Ida Gjervold Lunde, University of Oslo
Principal Supervisor
Michael Frisk, Postdoctoral fellow, University of Oslo
Summary
Temperature is routinely manipulated to control salmon growth in Norwegian aquaculture.
Lowering temperatures during freshwater rearing has been shown to improve cardiovascular morphology and increase growth following seawater transfer, offering a potential strategy to reduce pre-slaughter mortality, a persistent welfare and economic issue. However, few studies have examined even earlier temperature reductions or investigated their effects across the full production cycle.
This thesis investigated how early-life temperature regimes (embryonic and freshwater stages) influence cardiovascular health and lifetime performance in Atlantic salmon. Data from commercial facilities were analysed alongside echocardiography and ex vivo cardiac morphology assessments.
Lower egg incubation temperatures were associated with reduced hatchery mortality and fewer cardiac abnormalities at early life stages. At sea, fish from colder egg profiles showed less pronounced heart and skeletal muscle inflammation (HSMI) phenotypes, altered post-disease remodelling, and higher growth before slaughter. Fish reared at low freshwater temperatures with a winter signal and transferred during spring showed reduced mortality and fewer cardiac deviations, as well as greater resilience to stressful events such as delousing. However, larger studies are needed to account for variation across location and seasons.
Overall, adopting lower, more natural temperature profiles with seasonal fluctuations during egg incubation and freshwater rearing can reduce mortality, improve growth, and enhance cardiovascular health in farmed Atlantic salmon.
Additional information
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