Description: Two groups (n = 8, n = 5) of Polar cod (Boreogadus saida) were acclimated to both 0 and 6°C. The smaller groups were used to investigate specific dynamic action (SDA) (treatment "digestion"). Each fish of the larger groups was used for exercise tests in an unfed and fed state (treatment "exercise" and "exercise & digestion", respectively) at their respective acclimation temperatures as well as in a fed state acutely exposed to an intermediate temperature (3°C). SDA measurements lasted for 18 and 9 days at 0 and 6°C, identical to the food-deprivation period of B. saida in the exercise approach. Feeding was conducted in the common tank. Accordingly, daily rations reflect the mean food consumption per treatment. Each fish was allowed to feed for at least 2h before the start of the experiments. The acclimation time refers to the first day of the respective experiment. The SDA response is characterized by the maximum metabolic rate (MMR) evoked by digestion (defined as second record of oxygen consumption ṀO₂) and terminated by the standard metabolic rate (SMR) (20% quantile among ṀO₂ values obtained on the 18th day at 0°C and the 9th day at 6°C, respectively). Subsequently, the individual duration and the magnitude of the postprandial response (integral below the curve generated by aid of a specific script within the program R (R Core Team 2013)) was calculated. Fish used during exercise treatments were weaned to a Brett-type swimming tunnel for exactly two hours, before the onset of the exercise protocol. The exercise protocol involved a settling period of 5 min at a baseline swimming velocity, before the speed was carefully increased by 1.4 cm/s once per minute. Like this, the transition speed to partly anaerobic swimming (Ugait), as well as the critical swimming speed (Ucrit) was determined for every specimen. At each velocity step, burst-type swimming behavior was counted for 50 sec. The maximum burst count (max. BC) was used to estimate anaerobic capacities. As soon as Ucrit was reached, fish were placed in a separate respiration setup for the determination of MMR evoked by exercise and the MMR evoked by concomitant exercise and digestion (first ṀO₂ record after placement in respiration chamber) for 48 h. The respective SMR of unfed fish were calculated as 20% quantiles among all ṀO₂ records after 24 h. The difference between MMR and SMR values of exercised and postprandial fish represent the individual aerobic scopes (AS). The ṀO₂ at Ucrit (MMR) was used to calculate the energetic efficiency of maximum swimming performance (Emax).