Individual differences in metabolism predict coping styles in fish

Studies on metabolism usually rely on measurements of oxygen consumption obtained in respirometry chambers. Despite rigorous standardization there is still considerable inter-individual variation in metabolic rates which is often ignored. Furthermore, housing in respirometry chambers implies handling and exposure to a new environment, conditions known to be a source of stress in animals. The extent of stress response is known to be dependent on an individual's coping style. Therefore, the extent of individual variation in respirometry data may be related to the expression of coping styles. The goal of this study is to determine whether the variation in oxygen consumption after a stressor is the resultant of an individual's coping style. Our approach was to determine oxygen consumption in fish immediately after transfer to respiratory chambers and during the subsequent 22 h. In addition, the same individuals were subjected to 3 respirometry runs (22 h each) to address the question whether habituation occurs when fish are used in multiple runs and whether habituation potential is linked to coping styles. The same individuals were then subjected to an acute stressor and the escape behaviour and plasma cortisol were determined to assess coping style. Taken as a whole, the findings of this study suggest that individual variation in oxygen consumption in respirometry chambers are related to the expression of coping styles: individuals with higher oxygen consumption at the start and throughout the measurement period were shown to react passively (longer latency to escape) in a confinement stress. In addition, successive respirometry runs should not be assumed to result in habituation, as depending on an individual's coping style either habituation (in the case of passive copers) or sensitization (in the case of active copers) can occur. (C) 2010 Elsevier B.V. All rights reserved.