The influence of non-native salmonids on circulating hormone concentrations in juvenile Atlantic salmon

► Non-native salmonids may be hindering the reintroduction of Atlantic salmon to Lake Ontario. ► We found that non-natives led to higher stress hormone concentrations in Atlantic salmon. ► Conversely, non-native salmonids did not affect androgen concentrations. ► We also found that some Atlantic salmon strains may be better able to cope with competition. ► Of three candidates, the currently stocked strain was the most chronically stressed.