MUCOSAL HEALTH AND WELFARE OF ATLANTIC SALMON SMOLT IN LAND-BASED RECIRCULATING AQUACULTURE SYSTEM (RAS)

This Industrial PhD project is focusing on an important topic in Norway's land-based RAS aquaculture, impact of developing RAS technologies on smolt health, and smoltification process. The aim of this project is to characterize Atlantic salmon smolt in terms of stress, pathology, and immunology parameters, before and after the transition phase from freshwater to seawater. This research will aim to establish new potential biomarkers and define parameters that can expand fish health and welfare monitoring in land-based RAS, and at the same time reduce costs from losses of fish in intensive salmon farming. Smoltification is the most vulnerable stage during the life cycle of Atlantic salmon as in this period salmon smolt needs to adapt from the freshwater stage to the seawater stage of life. The status of the smolt mucosal health and welfare is especially important in this period. This transition from freshwater to seawater is quite demanding for smolt, and naturally, osmoregulatory capacity will be increased in order to better adapt to seawater. The timing of the transition is vital for the survival in seawater. Still, there are knowledge gaps about molecular changes that are important for physiological development. A standard monitoring tool for assessment of smolt development is gill enzyme assessment. Also other potential biomarkers could be tested and utilized for monitoring the smoltification. RAS salmon farming has a significant beneficial effect on fish welfare and health, compared to the traditional flow-through farming system. At the same time, RAS has its challenges for fish health which require further research. Three publications and PhD thesis are planned to be published. Overall aims are to achieve a better understanding of the smoltification process in smolt, analyze fish health and welfare in land-based RAS, identify a potential set of monitoring parameters to improve health and welfare, and to reduce fish loss in intensive RAS salmon production.

The overall objective of the project is to identify new biomarkers and characterize biological and physical parameters that can optimize fish health and welfare-monitoring in land-based recirculating aquaculture systems (RAS) and reduce costs from losses of fish in intensive salmon farming. RAS have significant beneficial effects on fish health and welfare in comparison with the traditional flow-through systems for Atlantic salmon farming. However, there are challenges for fish health with RAS and there is little industrial experience beyond the post smolt stage in land-based RAS. Improved monitoring of fish health and optimization of production are closely linked and lead toward more eco-friendly production of adult fish. Research findings suggest that smolt quality is a major determinant of survival in seawater and production performance. Smoltification occurs before the transition from hyper- to the hypo-osmotic environment and involves developmental changes in the physiology, biochemistry, morphology and behavior of juvenile salmon. Gills and intestine are the two most important osmoregulatory tissues in fish. This project aims to characterize Atlantic salmon smolt before and after the transition phase in RAS to establish biomarkers related to stress, pathology and immunology.