| Summary: | This thesis examines the effects of feeding level, water temperature and diet composition on growth and efficiency of feed utilization by rainbow trout and Atlantic salmon. Trout were fed either to near-satiation (NS) or at 85 (R1) or 70% (R2) of the amount of feed consumed in the previous week by NS fish at 6, 9, 12 and 15$\sp\circ$C. The total feed intakes were on average 76% (R1) and 65% (R2) of that of the NS group. Salmon reared at 15$\sp\circ$C were fed three diets with different protein/energy ratios at either 100% or 85% (feed requirement model). In both species, reducing feed allocated significantly reduced body weight gain. Feed efficiency, carcass composition, nitrogen, phosphorus and energy retention efficiencies (% DE) and waste outputs were not affected by feeding level or water temperature. The apparent digestibility of dry matter, nitrogen and energy of the diet significantly increased with increasing water temperature. Increasing the DE of the diet significantly increased feed efficiency and reduced total solids, total phosphorus and solid nitrogen waste outputs (g/kg gain). Efficiency of metabolizable energy utilization for growth (K$\sb{\rm pf}$) and the ratio of energy deposited as protein vs. lipid, were not affected by feeding level or temperature, but they were affected by diet composition.
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