The relationship between specific dynamic action and otolith growth in pike

Abstract

The hypothesis was tested that the daily increment width (IW) of the otolith comprises two components, one that correlates with basal metabolic rate (as has been demonstrated previously) and the other that correlates with apparent specific dynamic action (Rsda)(the post‐prandial elevation in metabolism). Simultaneous measurements of IW and metabolic rate before and after a meal were collected from individual pike Esox lucius. After feeding, IW and metabolic rate increased above basal levels for 5–6 days. There was no correlation between daily IW and Rsda, reflecting within‐individual difference in the shapes of the post‐prandial responses of the two variables. There was a significant relationship between the total changes of IW and metabolic rate integrated following meals. The magnitude of the post‐prandial response as a proportion of the basal level was larger for metabolic rate than IW, mirroring the previously reported responses of these variables to acute temperature change. This study suggests that analysis of IW has the potential to provide a historic record of energy intake but only when integrated over a period equivalent to the digestion time. Consideration of energy budget theory indicates that IW is unlikely to provide a robust record of short‐term somatic growth if activity metabolism is significant and variable.