Design of the behavioural experiments performed on first-feeding Arctic charr (Salvelinus alpinus).

Two experiments were performed. Fish were observed for foraging behaviour and mobility every week for four consecutive weeks (63, 70, 77, 84 days post hatching). Each weekly observation consisted of repeated measures of the individual over two days. Experiment A was conducted on fish raised in groups. Each observation was conducted on one fish (within a group of 6 fish) or one fish isolated 24 h before the observation (brief isolation). Naïve fish were used every week. Experiment B was conducted on fish isolated before hatching (i.e. long-term isolated, repeated measures on the same individuals).