Abstract
Growth hormone (GH) has multiple targets and diverse effects in vertebrates. It is a principal promoter of growth, and also influences the metabolism. During the past years, it has become clear that GH alters the behaviour of fish as it increases appetite, swimming activity, aggression, and reduces anti-predator behaviour. To clarify the mechanisms behind these effects, further research is required. However, it seems that GH increases swimming activity by a direct action on the brain and/or by a peripheral mediator, whereas appetite is affected via a secondary, peripheral factor. Similar to mammals, present data indicate that GH affects dopaminergic activity in the hypothalamus in salmonid fish. Whether this is a mechanism whereby GH influences behaviour remains to be elucidated.
