What is a successful fish? Determinants of competitive success in Arctic char (Salvelinus alpinus) in different social contexts

In tests between pairs of 0+ Arctic char (Salvelinus alpinus) there was a clear relationship between aggressiveness and ability to monopolise a localised and limited food resource. However, indices of competitive ability in pairwise tests in observation arenas where food was highly limited did not predict performance (growth, age of maturation, or reproductive investment) when the same fish were housed under routine husbandry conditions (i.e., at high densities and fed to excess). This is in direct contrast with the results of similar studies conducted on Atlantic salmon (Salmo salar), where social suppression of food acquisition occurs despite high food availability. It is suggested that different behavioural traits promote success in different competitive environments and that these do not co-vary at the individual lever in char.