How did the research turn out? What were the findings? Researchers themselves report briefly on the research they have undertaken with funding support from the Formas Research Council.
Editor: Margaretha Nordahl
Stress coping strategies in brown trout. Ecological significance and the effects of sea ranching
Svante Winberg (project leader)
Summary of results from Uppsala University.
Email: svante.winberg@ebc.uu.se
In many animal species, individuals exhibit different reactions to the same type of stress. The way individuals react appears to be largely genetically determined, but it is also influenced by the conditions during growth. Proactive stress coping comprises e.g. aggressive behaviour and greatly elevated sympathetic activity, and also a relatively small rise in the plasma levels of cortisol. Animals with reactive stress coping, on the other hand, exhibit little or no aggressive behaviour and only a weak rise in sympathetic activity, but a very strong rise in blood cortisol when they are threatened.
It has recently been demonstrated that sea ranching of brown trout results in behavioural changes and neuroendocrine stress responses. If sea ranching results in a selection for a certain stress response, this may have serious consequences for the diversity of brown trout populations; this gives rise to worries that cultivation may cause a loss of genetic variation and that the cultivated strain will diverge from the wild phenotypical norm. This worry is of special topicality since sea ranched salmon today account for a considerable proportion of the total stock.
All in all, the results from the project corroborate the hypothesis that different stress coping strategies exist in fish and that there are differences in the frequency of stress coping styles between different populations of brown trout.
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