Behaviour, in particular aggressive interactions between individuals,
can be energetically costly. For Salmonids, this has been demonstrated
by increased energetic expenditure associated with agonistic behaviour
in sockeye salmon Oncorhynchus nerka (Brett, 1964) and rainbow trout
Oncorhynchus mykiss (Lefrancois et al., 2001; Li and Brocksen, 1977).