Abstract
Abstract Standard oxygen consumption was greater in parr than in smolts throughout the freshwater growth period February–July 1987. However, the weight-specific rate, corrected for differences in body size, was markedly higher in smolts than in parr. Routine O 2 consumption showed an endogenous circadian rhythm initially, in both parr and smolts. Metabolic activity was markedly higher in daylight than in darkness. The diurnal increase in O 2 consumption was correlated with sunrise, and its duration with daylength. However, in smolts this circadian rhythm was replaced by a multi-peak pattern after normal smolting time, suggesting that preventing seaward migration induced physiological disturbance. The influence of temperature on both standard and routine O 2 consumption decreased gradually during seasonal warming. However, this thermal acclimation was much less apparent at smolting, when the increase in metabolic activity could be related to endocrine changes.
Published Version
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