Long-term separate and combined effects of environmental hypercapnia and hyperoxia in Atlantic salmon (Salmo salar L.) smolts

By termination of the FW period, the HO2 group had significantly higher body weight than all other groups (p < 0.05), with specific growth rate significantly higher than the CO2 groups (p < 0.05). Further, the condition factor was significantly lower in all the CO2 groups at the end of the FW period compared to the control and normcapnia groups (p < 0.05). Although variable among replicates, occurrence of nephrocalcinosis was 10 times higher in the hypercapnia groups than in the control and normcapnia groups. Mortality was negligible (< 2.0%) during the trial, and most of the mortality occurred following SW transfer.