Growth trajectory influences temperature preference in fish through an effect on metabolic rate

Most animals experience temperature variations as they move through the environment. For ectotherms in particular, temperature has a strong influence on habitat choice. While well-studied at the species level, less is known about factors affecting the preferred temperature of individuals. Especially lacking is information on how physiological traits are linked to thermal preference and whether such relationships are affected by factors such feeding history and growth trajectory. This study examined these issues in the common minnow Phoxinus phoxinus, to determine the extent to which feeding history, standard metabolic rate (SMR) and aerobic scope (AS), interact to affect temperature preference. Individuals were either: 1) food-deprived for 21 days, then fed ad libitum for the next 74 days; or 2) fed ad libitum throughout the entire period. All animals were then allowed to select preferred temperatures using a shuttle-box, and then measured for SMR and AS at 10°C, estimated by rates of o...