The effect of carbon monoxide (CO) as stunning method in Atlantic salmon ( Salmo salar L.) on stress indicators (adrenaline, A; noradrenaline, NAD) and on fillets quality during the shelf life has been investigated. The CO was dissolved into tanks with salmon for 8 and 20 min to obtain fish groups CO8 and CO20, respectively. These groups were compared to a non-stressed control group (C). All the fish were hauled out from the tank and killed by percussion. Adrenaline content of CO20 group was 1.8 and 1.7-fold higher than CO8 and C groups respectively (P < 0.001), which exhibited similar values. Noradrenaline content was higher in CO20 than in C group (8.1 vs . 5.4 ng/ml plasma; P < 0.0001). The CO treatment resulted in a small significant increase in lightness and yellowness, not altering the overall “natural” colour of the fillet. CO treatment caused a rapid onset of rigor mortis and a small but significant increase in drip loss (P < 0.05). [ABSTRACT FROM AUTHOR]