This thesis explores the behavioural and physiological effects of elevated carbon dixoide (CO2) on freshwater, juvenile samonids. Arctic Charr, Rainbow Trout, and Brook Charr were each exposed to elevated CO2 over a two week period. During this time, metabolic rate, growth, and behaviour were monitored. Feeding and tissues were examined after the exposure period. Generally, few effects of CO2 were observed; however, Arctic Charr had higher standard metabolic rate as a result of the CO2 exposure. Additionally, Arctic Charr gills showed signs of tissue damage that may have been due to the CO2 exposure. Overall, my findings suggest that short-term elevated CO2 may not be harmful for juvenile salmonids in freshwater. Future studies should explore longer and higher CO2 exposures, and the relationship between elevated temperature and CO2.