Metabolic rate, social status and life-history strategies in Atlantic salmon

An animal's relative social status has major short- and long-term consequences, yet its determinants are rarely known. Here a strong relationship between status and standard metabolic rate (SMR) in juvenile Atlantic salmon,Salmo salar, is demonstrated; the higher the SMR, the more dominant the fish. After controlling for SMR, the relative size, weight or date of first feeding of two opponents had no effect on the outcome of encounters. Moreover, these differences in SMR are not a consequence of experience in encounters, since it has previously been shown that the onset of aggressive behaviour occurs later. Since relative social status has a significant influence on subsequent developmental pathways in this species, these results indicate an indirect link between intraspecific variation in metabolic rates and life-history strategies.