Growth hormone reduces growth in free-living Atlantic salmon fry
Article first published online: 10 MAY 2012
© 2012 The Authors. Functional Ecology © 2012 British Ecological Society
Volume 26, Issue 4, pages 904–911, August 2012
How to Cite
Sundt-Hansen, L., Einum, S., Neregård, L., Björnsson, B. T., Johnsson, J. I., Fleming, I. A., Devlin, R. H. and Hindar, K. (2012), Growth hormone reduces growth in free-living Atlantic salmon fry. Functional Ecology, 26: 904–911. doi: 10.1111/j.1365-2435.2012.01999.x
- Issue published online: 16 JUL 2012
- Article first published online: 10 MAY 2012
- Received 28 March 2011; accepted 26 March 2012 Handling Editor: Keith Sockman
- growth enhancement;
- life history;
- Salmo salar;
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 organism’s 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.