The smolt probe - novel tools for assessment of smolt quality and marine performance in Atlantic salmon

Smolt quality is critical for successful salmon aquaculture, and poor smolt quality may generate a wide range of problems; increased mortality in seawater, increased vulnerability to diseases and poor growth, which in total represents a considerable loss. Therefore, the salmon industry continuously seeks practical, cost and time efficient methods to predict the ability of smolts to survive and grow in seawater. Due to its key role in the development of hypo-osmoregulatory ability, gill Na+,K+-ATPase (NKA) activity has become a widely used measure of smolt quality. The proposed project seeks to enhance our understanding of the underlying genetic mechanisms controlling the development of NKA, with emphasis on the critical changes in alpha (a) subunit a1a an d a1b isoforms and seawater tolerance in Atlantic salmon during smoltification and seawater adaptation. The proposed project will seek to develop new molecular methods for precise determination of smolt quality, which will secure a higher degree of accura cy in defining the optimal time for seawater transfer, further decreasing losses due to mortality and poor growth, and also act as an early warning on signs of desmoltification. Our scientific approach includes the development and refinement of tools and establishment of protocols for large-scale absolute quantification of NKA a1a and a1b, and to characterise normal developmental trajectories for the expression of these key genes during parr-smolt transformation in Atlantic salmon. Parallel to, and integr ated with, the development of novel tools is the evaluation of these methods under a range of scenarios which are highly relevant to the aquaculture industry, with focus on the impact of water quality (acid/Al), desmoltification and handling/transport. Th ese scenarios are designed to provide groups of smolt known to differ in quality, providing excellent experimental models for the assessment of predictive value of post-smolt performance.