Is the adipose fin and the lower jaw (kype) related to social dominance in male Arctic charr Salvelinus alpinus?

This study reports on the importance of the size of the kype (lower jaw) and the adipose fin for establishing and maintaining social dominance in pair‐wise interactions among size‐matched, reproductively active male Arctic charr Salvelinus alpinus. The size of these traits seems not to have a large influence on establishing dominance, but after 4 days of social interactions, and after dominance rank is established, subordinate males show reduced size of their adipose fins and kypes relative to that of dominant males. Consequently, these traits seem to be costly labile characters that could be of importance in inter and intra‐sexual evaluations of individual quality.