To what extent do acute exposure and acclimation to cold temperatures impact the cardiorespiratory capacity, stress response and swimming performance of Atlantic salmon (Salmo salar)

Limited research has been conducted on the physiology of Atlantic salmon (Salmo salar) at cold temperatures despite significant winter mortalities at sea-cage sites in Atlantic Canada. Thus, I performed two experiments to investigate how acclimation to 8, 4 and 1°C, and acute cooling from 8-1°C, affected the Atlantic salmon’s cardiac function, metabolic capacity, stress physiology and swimming performance. While this research shows that exposure to 1oC causes stress, and significantly reduces their metabolism and swimming performance, it also reveals that there is significant flexibility/plasticity in how salmon modulate heart function when acutely vs. chronically exposed to cold temperatures. For example, the experiments were performed on salmon from two different aquaculture companies, and changes in resting heart rate and size were only seen in 1oC acclimated fish in Chapter 3. This data suggests that responses to cold temperatures differ between cultured salmon populations. Further, how salmon meet the energetic demands of exhaustive exercise depends on the duration of cold exposure [e.g., fish acutely cooled to 1℃ predominantly enhance tissue oxygen extraction, whereas those acclimated to this temperature increase stroke volume]. These studies add greatly to our understanding of how temperatures close to a salmon’s (fish’s) lower thermal limit impact its physiological capacity and the mechanisms involved