Farmed fish display genetic differences from wild fish in a variety of morphological, behavioural and physiological traits as a result of the domestication process and selective breeding. Farmed salmon typically outgrow wild salmon by large ratios under hatchery conditions, although observed growth differences are much less in the wild. It is possible that farmed salmon have become adapted to regulated domestic environments, while concurrently they are unable to perform as well in more variable wild environments. Escaped farmed salmon interact with wild salmon through resource competition and disease transmission, and can interbreed with wild salmon. The introduction of mal-adapted domestic genotypes into wild populations can lower their productivity. Comparative studies that assess the effects of hybridisation on life-history traits linked to fitness are important in understanding how interbreeding will affect the resilience of wild populations. The present thesis investigated the freshwater growth and survival of multiple families derived from various farmed, wild and F1 hybrid salmon populations when reared at contrasting (1) temperatures, (2) densities and rearing conditions, (3) food availabilities, and (4) diets. In all experiments farmed salmon outgrew wild and hybrid salmon, and their hybrids displayed intermediate growth. Relative growth differences detected at contrasting temperatures were population-specific; indicating that the competitive balance between conspecifics may depend upon genetic background and river temperature. Findings highlight the merits of adopting a more spatially resolved approach to risk management of wild populations. In all other experiments the relative growth differences among groups did not differ across treatments, indicating that farmed fish have retained their plasticity in response to respective experimental treatments. Although experiments were conducted under controlled conditions, findings suggest that the investigated treatments are not individually responsible for elevated growth differences observed in hatchery conditions or the lower growth differences observed between farmed and wild salmon in the wild.