Effects of body size and temperature on metabolism of bream compared to sympatric roach

Standard (SMR) and routine (RMR) metabolic rates (mg O2 h−1) of bream, Abramis brama, were measured over a wide range of fish sizes and water temperatures (1-560 g wet mass, 5-23°C) by automated, computerised intermittent flow respirometry. These data were compared to similar data collected on roach, Rutilus rutilus, a sympatric species within the same subfamily Leuciscinae (Cyprinidae). For bream, both SMR and RMR were described by allometric mass exponents of 0.70 and exponential temperature dependencies over the entire size and temperature range. In bream, the temperature dependency of SMR and RMR was described by a Q10 of 2.8 and 2.2, respectively, while roach displayed Q10 values of 2.4 and 1.9, respectively. There were small but significant differences between bream and roach in the temperature dependency of SMR. Between 5 and 10°C, juvenile roach (Q10 = 5.8) and adult bream (Q10 = 4.9) displayed significantly higher sensitivity of mass-independent RMR to temperature changes than equal-sized juvenile bream and adult roach, respectively. This indicates different strategies during winter and the early spring period. When comparing these results with related literature about energy intake, it appears that roach and bream have evolved different thermal phenotypes, with bream showing a slightly more pronounced increase of metabolic energy loss and a less pronounced increase of energy intake (consumption, digestion) with temperature compared to sympatric roach.