Has a 4-generation selection programme affected the social behaviour and growth pattern of Arctic charr (Salvelinus alpinus)?

Domestication and selection to enhance growth of animals is likely to affect social behaviour. Aggression may increase or decrease. A 4-generation selection programme on the salmonid species Arctic charr (Salvelinus alpinus L.) based on a well-defined population origin has made it possible to compare the social behaviour of its progeny with progeny from wild parents of the same population, thus excluding the effects of population differences. During 5 months, the within-group growth variation and specific, defined behaviour parameters were observed and analysed under experimental conditions where dominance hierarchies are promoted. In such conditions, which are opposite from farming conditions created to reduce dominance hierarchies, there was no difference in mean growth rate during the observation period and no difference in the social structure (number of dominant, subdominant and subordinate individuals) in the groups. Also, the level of within group aggression did not appear significantly different between level of domestication when observed between or during feeding periods. However, there was a significantly larger growth variation in the progeny of wild parents compared to the selected progeny. Also, the level of aggression increased significantly only in the groups with a selected origin during feeding events compared to periods in-between feeding. Individuals in the wild origin groups showed a significantly higher level of a passive low-profile behaviour compared to the selected origin groups. These differences suggest that selection for fast growth in farming conditions reduces the frequency of subordinate individual behaviour resulting in a smaller intra specific difference in growth in farm strains.