Differences in pathogen resistance within and among cultured, conservation-dependent, and endangered populations of Atlantic salmon, Salmo salar L.

We report genetic differences for resistance to the pathogen Listonella anguillarum within and among one cultured and two wild Canadian populations of Atlantic salmon, Salmo salar, using a common-garden experimental protocol. Following exposure to the causative agent for vibriosis, parr originating from the endangered Stewiacke River population experienced significantly higher mortality than cultured parr, four generations removed from the Saint John River population, and wild parr from Tusket River. Pathogen resistance differed between sexes; males consistently experienced higher survival than females. There was no evidence that maturity influenced pathogen resistance in male parr. The population and sex differences in pathogen resistance documented here have implications for risk assessments of the demographic consequences of interbreeding between wild and farmed Atlantic salmon.