The effects of chronic plasma cortisol elevation on the feeding behaviour, growth, competitive ability, and swimming performance of juvenile rainbow trout

T. Ryan Gregory, Chris M. Wood

Research output: Contribution to journalArticle

172 Citations (Scopus)

Abstract

Plasma cortisol elevation, a common consequence of stress, occurs in salmonids of subordinate rank; these fish acquire a smaller share of available food and grow more slowly. This study examined the role of cortisol itself in these phenomena. Cortisol implants, with parallel sham and control treatments, were used to create a chronic threefold elevation in plasma cortisol levels in juvenile rainbow trout, and the individual feeding patterns of the fish were evaluated using X-ray radiography. The three treatment groups were (1) held alone and fed to satiation, thereby providing a measure of voluntary appetite, or mixed together in equal proportions and fed to either (2) satiation or (3) half-satiation, thereby allowing assessment of the additional effects of competitive interaction and food limitation. Chronic plasma cortisol elevation had significant negative effects on individual appetite, growth rate, condition factor, and food conversion efficiency, independent of whether the fish were held under unmixed or mixed conditions. Under the latter, mean share of meal was reduced and fin damage increased in cortisol-treated fish; negative growth effects were more severe with food limitation, but the response patterns were otherwise unchanged. Even in the absence of other groups, cortisol-treated fish showed more variable feeding patterns. When compared at the same individual ration levels, cortisol-treated fish had lower growth rates, reflecting a higher 'cost of living.' Cortisol treatment had no effect on aerobic swimming performance. These results suggest that the structure of the feeding hierarchy may not be determined solely by competitive ability but may also be greatly influenced by differences in the feeding behaviour of unstressed fish versus stressed fish caused by cortisol elevation in the latter.

Original languageEnglish
Pages (from-to)286-295
Number of pages10
JournalPhysiological and Biochemical Zoology
Volume72
Issue number3
DOIs
StatePublished - Dec 1 1999

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Aptitude
Oncorhynchus mykiss
Feeding Behavior
feeding behavior
cortisol
Hydrocortisone
long term effects
Fish
Plasmas
Fishes
Growth
Satiation
fish
satiety
Appetite
appetite
Food
Swimming
Food-Drug Interactions
X ray radiography

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Physiology
  • Physiology (medical)

Cite this

The effects of chronic plasma cortisol elevation on the feeding behaviour, growth, competitive ability, and swimming performance of juvenile rainbow trout. / Gregory, T. Ryan; Wood, Chris M.

In: Physiological and Biochemical Zoology, Vol. 72, No. 3, 01.12.1999, p. 286-295.

Research output: Contribution to journalArticle

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