Individuelle forskjeller i strategier for håndtering av stress hos salmonider - betydning for akvakultur

We recently examined individual variation in the effect of stress on feed intake in rainbow trout (Oncorhynchus mykiss) after stress, and observed strong correlations between feeding in a novel environment and other behavioral and physiological traits. For instance, fishes that quickly resumed feeding were more aggressive and competitive than slower individuals. Quick individuals also showed a decreased plasma cortisol and brain serotonin response to stress. Serotonin is central for normal emotion and cognition in mammals, through its effect on brain structural processes and neuronal flexibility. Our data therefore suggest that animal welfare under conditions of group rearing carries over to determine individual behavior in isolation. Stress resistance is inheritable in both rainbow trout and Atlantic salmon, but there may be subtle differences between the biology of these species that affect their performance in aquaculture. In Norway Atlantic salmon provide a better animal model for selection studies, since both pedigree information and wild-type reference populations are still available. Thus, the main objective of this project is to create high- and low stressresponsive families of Atlantic salmon and utilize these fish in fundamental studies of fish neurophysiology and individual welfare criteria, as well as evaluating their performance under commercial rearing conditions. We will investigate if the association between low stress responsiveness and high aggression can be avoided by targeted selection, and whether welfare and production parameters are improved in lowresponsive fish. The selection response will be measured in laboratory studies, while performance in aquaculture will be adjudged under conditions of commercial rearing. The project combines behavioral observations, analysis of brain serotonin metabolism, and gene expression related to brain structural processes as indicators of cognitive function and the emotional state. Summary of project goals and deliverables The principle objective is to create high and low stress-responsive families of Atlantic salmon and elucidate whether increased aggression can be avoided, and welfare and production parameters can be improved, in the low-responsive line. The sub-goals are I. To investigate whether the previously observed association between reduced stress responsiveness and increased aggression can be dissociated by targeted selection II. To investigate whether there is a welfare advantage of using low-responsive fish in aquaculture, by employing a combination of behavioral and neurophysiological welfare indicators III. To investigate whether there is a production advantage of using low-responsive fish in aquaculture, by studying robustness and growth patterns at all stages of the rearing cycle