Can metabolic rate explain context-dependent performance of farmed salmon?

Escaped farmed Atlantic salmon interbreed with wild Atlantic salmon in nature. The performance of the resulting offspring often differs from that of pure wild juveniles. In addition, their presence can affect the performance of wild salmon juveniles negatively. We hypothesize that these findings may relate to changes in metabolic rate (the energetic cost of self-maintenance) that have occurred during the domestication process. Furthermore, since environmental conditions determine what MR levels are advantageous, the performance of farmed offspring, as well as their effect on wild juveniles, may be context dependent. To test these hypotheses, we first compare the mean levels of metabolic rate of pure farmed, farmed-wild hybrids and pure wild offspring at the embryo and early juvenile life stages. Next, in controlled, semi-natural environments, we test (1) the performance (in terms of survival and growth) of hybrid juveniles relative to that of their wild half-siblings, (2) whether the presence of hybrids affect the performance of their wild half-siblings, and (3) whether any such effects depend on the environmental context (represented by manipulated food availability). Results from these analyses will be presented.