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Growth hormone reduces growth in free-living Atlantic salmon fry

Journal article
Authors L. Sundt-Hansen
S. Einum
Lena Neregård
Björn Thrandur Björnsson
Jörgen I Johnsson
I. A. Fleming
R. H. Devlin
K. Hindar
Published in Functional Ecology
Volume 26
Issue 4
Pages 904-911
ISSN 0269-8463
Publication year 2012
Published at Department of Biological and Environmental Sciences
Pages 904-911
Language en
Links dx.doi.org/10.1111/j.1365-2435.2012...
Keywords growth enhancement, juveniles, life history, Salmo salar, trade-offs, conflicting selection pressures, trout oncorhynchus-mykiss, brown trout, rainbow-trout, ontogenic conflict, increases growth, trade-offs, salar, wild, size, rting tl, 1989, ecology, v70, p587, lean e, 1992, aquaculture, v103, p377
Subject categories Ecology

Abstract

1. Although life-history theory predicts that juvenile growth rates should be high, there is substantial evidence that most juveniles grow below their physiological maximum. The endocrine system plays an important role in the determination of fundamental life-history traits, and hormones often serve as a link between an organisms environment and the expression of a trait. Particularly, growth is a life-history trait, which is strongly associated with growth hormone (GH) in fish, as well as most vertebrates. 2. To elucidate trade-offs related to elevated GH in fish in a natural environment, we experimentally administrated GH exogenously to juvenile Atlantic salmon using sustained-release GH implants, at an earlier ontogenetic stage than previously achieved (1.5 months). We assessed the effects on growth, dispersal and survival in contrasting environments. 3. Exogenous GH treatment increased the growth rate when fish were fed ad libitum in captivity. However, in a natural stream, GH treatment had a significant negative effect on growth and no apparent effect on survival or dispersal. This contrasts with previous studies conducted at later developmental stages, which show either a positive growth effect or no effect of elevated GH levels. 4. This study shows that environmental conditions strongly affect the response to GH and that under some natural conditions, it may also reduce growth. We suggest that the endogenous plasma GH levels may be maximizing growth during early, but not later, juvenile stages in nature.

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