The bioenergetics of density-dependent growth in Arctic char (Salvelinus alpinus)

We explored the mechanisms of density-dependent growth in Arctic char (Salvelinus alpinus) by comparing the energetics of growth, consumption, and activity obtained under three replicated density treatments in a large-scale enclosure (90 m(2) surface area) experiment. The enclosures permitted the entry of zooplankton and allowed char to feed on the bottom and at the surface of the lake. We found a negative (power) relationship between growth and density. Char consumption rate decreased linearly with increasing density. Growth efficiency was affected by fish density in a similar manner as growth rate. Finally, activity increased with fish density and was particularly high at high densities. Our findings illustrate the complexity of the relationships among consumption, activity, growth rates, and fish density and bring further evidence to the possible involvement of behavioural mechanisms in density-dependent processes, notably by modulating activity costs with density.