Frisk, Michael1; Steffensen, John Fleng3; Skov, Peter Vilhelm1
1 National Institute of Aquatic Resources, Technical University of Denmark2 Section for Aquaculture, National Institute of Aquatic Resources, Technical University of Denmark3 University of Copenhagen
The magnitude and kinetics of the postprandial metabolic response are strongly affected by temperature. From an aquaculture perspective, it is of interest to determine the temperature at which the lowest digestive energy expenses occur. We have previously demonstrated that the optimal aerobic scope for pikeperch ranges between 11°C and 27°C. The aim of the present study was to investigate the thermal biology of pikeperch, by examining how specific dynamic action (SDA) and total ammonia nitrogen excretion (TAN) are affected by temperature, within this optimal temperature range.From oxygen consumption rate and TAN excretion measurements, we established nitrogen quotients at 13°C, 19°C, and 25°C. Nitrogen quotients were used to calculate instantaneous protein catabolism at the different temperatures. We found, that protein usage (17%–29%) was unaffected by temperature during fasting, but increased significantly in the course of digestion, where it became the main energy source at all experimental temperatures. Energy spent on digestion and the relationship between excreted and ingested nitrogen were unchanged with temperature. However, SDA was of shorter duration at 19°C than at 13°C, and a smaller fraction of metabolic scope was utilized for digestion at 19°C, compared to at 25°C. We therefore conclude that 19°C is a more favorable metabolic temperature for this species.