Post‐exercise metabolic rate in Atlantic cod and its dependence upon the method of exhaustion

This study tests whether or not post‐exercise oxygen consumption rates (Mo2) in fish are dependent upon how exhaustion is induced. A group of eight Atlantic cod (Gadus morhua) were each exercised using (1) a critical swimming speed (Ucrit) protocol, (2) an exercise protocol designed to measure anaerobic capacity of fish (Uburst), and (3) a protocol in which the fish were chased to exhaustion manually. Mo2 was measured for a 2‐h period following exhaustion induced by all three exercise regimes (Ucrit, Uburst and chase). Post‐exercise Mo2 following exhaustion from the Uburst and chase protocols were significantly higher than post‐exercise Mo2 following the Ucrit protocol. Each fish during the Ucrit protocol exhibited maximal Mo2 during exercise rather than during recovery, yet 75% of the fish during Ubrust recovery and 100% during chase recovery exhibited Mo2 higher than that measured during Ucrit exercise. These results, as well as the large interindividual variations in Mo2 among the eight fish, show that post‐exhaustion Mo2 is specific to the exercise regime employed, thus, investigators must exercise caution when combining results from different exercise protocols and/or individuals.