Clocks and immunity in Salmon

Atlantic salmon (Salmo salar) perform a profound developmental transition as they prepare to migrate from river to sea. This process, known as smoltification, is carefully timed to occur at the opportune time of year through sensitivity to changing photoperiod (day-length), and delivers a marine-adapted phenotype. In aquaculture settings, smoltification suppresses the immune system, and in particular, suppresses the gill immune transcriptome. This phenomenon is puzzling, the sea is awash with parasites and pathogens from which the salmon must protect itself, so suppressing its defenses makes little sense.


There are two likely interpretations of these data:

1.      Smoltification-associated immune-reprogramming is a natural, adaptive response, possibly to avoid overstimulation of the immune system upon seaward migration

2.      Aquaculture methods stimulate an abnormal immunosuppressive response to photoperiod-driven smoltification

As a part of ASTI theme 2 (‘comparative seasonal chronobiology’), we seek to test this second interpretation. Aquaculture lighting regimes use several weeks of constant light exposure. A choice which increases growth rate, but which in mammals, disrupts the circadian clock – bringing serious negative consequences for health and the immune system. Using complementary in vitro and in vivo techniques, we will test the role of the circadian clock in the salmon immune response and contrast ‘chronodisruptive’ standard aquaculture lighting profiles with our own ‘chronosympathetic’ designs.

This project also operates within ASTI theme 3 (‘one health’). More than 50 million farmed salmonids died upon transfer to sea cages last year in Norway alone. Better understanding of the interaction between aquaculture lighting regimes, the salmonid circadian clock, and their immune system could dramatically improve this statistic, with clear benefits for both animal welfare and food production efficiency.


Alex West (Principal investigator)
David Hazlerigg

Financial/grant information:

This work is funded through ASTI