Åberg, Madelene, Uniza Kahn, John Fleng Steffensen, Øyvind Øverli, Hans Magnus Gjoen and Erik Höglund

Abstract: Proactive and reactive stress coping styles is widespread amongst animal groups. Reactive individuals are generally shy and subordinate whereas proactive individuals show the opposite behavior. In salmonids, differences in larval development have been related to these styles. In this study we investigated larval development and time to emergence in two strains of Rainbow trout selected for low (LR) and high (HR) post stress plasma cortisol levels. These strains have previously been characterized with proactive and reactive stress coping, respectively. A line specific SNP was used to distinguish the emerging larvae and a clear link between stress coping style and emergence time was demonstrated by LR larvae emerging earlier than HR larvae. LR larvae also had more yolk reserves at the time of emergence. Establishing territories and energy reserves are important factors for inducing social dominance, raising the question about the effect of initial social experience in shaping Salmonide behavioral profiles