Dynamics of BK channel expression in gills during smoltification of Atlantic Salmon under farm conditions

Abstract

Smoltification is a crucial step in the aquaculture of Atlantic salmon. Currently, the Na+/K+ ATPase (NKA) test is used to determine whether fish have adapted to seawater when moved from freshwater. The mortality rate of unadapted fish in Chile is ~10% after smoltification. During this period, BK channel expression decreases in gills after two weeks in saline water under laboratory conditions. However, these findings have not yet been tested on an industrial scale. We characterized the changes in mRNA levels of BK channels in gills from Salmo salar during smoltification using salmon farming protocols and compare these results against gill NKA activity and found a significant decrease in expression of BK channel transcripts during the smolt stage. We also characterized the dynamic of the BK channel expression (mRNA) versus NKA activity by using transcriptomic and RT-PCR analyses under an industrial setting. BK channels are involved in a variety of physiological processes, and our results indicate that BK potassium channel expression in gills could form the basis of a new complementary test to determine the level of smoltification more precisely.