The effect of temperature and body size on metabolic scope of activity in juvenile Atlantic cod Gadus morhua L.

Changes in ambient temperature affect the physiology and metabolism and thus the distribution of fish. In this study we used intermittent flow respirometry to determine the effect of temperature (2, 5, 10, 15 and 20 degrees C) and wet body mass (BM) (similar to 30-460 g) on standard metabolic rate (SMR, mg O-2 h(-1)), maximum metabolic rate (MMR, mg O-2 h(-1)) and metabolic scope (MS, mg O-2 h(-1)) of juvenile Atlantic cod. SMR increased with BM irrespectively of temperature, resulting in an average scaling exponent of 0.87 (0.82-0.92). Q(10) values were 1.8-2.1 at temperatures between 5 and 15 degrees C but higher (2.6-4.3) between 2 and 5 degrees C and lower (1.6-1.4) between 15 and 20 degrees C in 200 and 450 g cod. MMR increased with temperature in the smallest cod (50 g) but in the larger cod MMR plateaued between 10, 15 and 20 degrees C. This resulted in a negative correlation between the optimal temperature for MS (T-opt) and BM, T-opt being respectively 14.5, 11.8 and 10.9 degrees C in a 50, 200 and 450 g cod. Irrespective of BM cold water temperatures resulted in a reduction (30-35%) of MS whereas the reduction of MS at warm temperatures was only evident for larger fish (200 and 450 g), caused by plateauing of MMR at 10 degrees C and above. Warm temperatures thus seem favourable for smaller (50 g) juvenile cod, but not for larger conspecifics (200 and 450 g). (C) 2014 Elsevier Inc. All rights reserved.