Fish Physiology and Biochemistry

, Volume 10, Issue 2, pp 111–122

Circadian pattern of hepatosomatic index, liver glycogen and lipid content, plasma non-esterified fatty acid, glucose, T3, T4, growth hormone and cortisol concentrations in Oncorhynchus mykiss held under different photoperiod regimes and fed using demand-feeders

  • T. Boujard
  • J. F. Leatherland

DOI: 10.1007/BF00004522

Cite this article as:
Boujard, T. & Leatherland, J.F. Fish Physiol Biochem (1992) 10: 111. doi:10.1007/BF00004522


The circadian patterns of several tissue and plasma metabolites, and several plasma hormone concentrations are described in rainbow trout (Oncorhynchus mykiss) that were held in groups under three different photoperiod regimes, and given free access to a demand-feeder. Regardless of photoperiod regime, all the measured parameters showed significant diel rhythms that appeared to be synchronized by dawn; dawn was represented by the concomitant onset of both light and feeding. The diel increases in hepatic glycogen content, and plasma T4 and cortisol concentrations were in phase with the main period of feeding activity, whereas the peaks in plasma T3 and glucose concentrations that may also be triggered by feeding activity, were delayed by several hours. The peaks in hepatosomatic index, plasma non-esterified fatty acids and plasma growth hormone concentrations were 180° out of phase with the main period of feeding activity, and associated with periods of hypophagia and low activity.


circadian rhythmsdiel cyclesfeeding timedemand feederfishglycogenlipidliver weightfatty acidsglucoseT3T4growth hormonecortisol

Copyright information

© Kugler Publications 1992

Authors and Affiliations

  • T. Boujard
    • 1
  • J. F. Leatherland
    • 1
  1. 1.Institute of Ichthyology, Department of ZoologyUniversity of GuelphOntarioCanada
  2. 2.INRA HydrobiologieAscainFrance