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Fig. 1. The number of aggressive acts performed during each daily observation
session (A) and the total number of aggressive acts (B) performed during four
daily 5 min observation sessions by the socially dominant fish during social
interaction in size-matched pairs of Arctic charr interacting on white or
black backgrounds. Values are means ± S.E.M., N=7 pairs on a
white and N=7 pairs on a black background. Different letters indicate
a significant difference (P<0.05; MannWhitney
U-test).