A swim tunnel is to fish as a treadmill is to humans, and is a device used for indirect measuring of the metabolic rate. This study aims to explore the fish stress (if any) during the critical swimming test routines (fish handling, confinement, and swimming) using heart rate ( f H , heartbeat per minute) bio‐loggers in farmed Atlantic salmon ( Salmo salar L.). In addition, the recovery dynamics of exercised fish using f H were...