Evaluation of lipid sources in diets fed to bull trout,Salvelinus confluentus

To aid in development of nutritionally complete diets, a 12‐week experiment was conducted to identify appropriate sources of dietary lipid for bull trout. The basal diet was top‐coated with marine fish oil (MFO) (pollock liver oil), canola oil (CO), linseed oil (LO) or a mixture of canola and linseed oils (CLO) to produce four treatments. Each diet was fed to triplicate groups of fish initially averaging 1.6 g per fish. Weight gain, feed efficiency, survival and carcass proximate composition were not significantly different among fish fed the dietary treatments. However, whole‐body fatty acid percentages varied significantly among fish fed the four diets. Whole bodies of fish fed diets with vegetable oil (VO) contained significantly higher 18:2n‐6, 18:3n‐3 and total n‐6 polyunsaturated fatty acid percentages and significantly lower 20:5n‐3, 22:6n‐3 and total saturated fatty acid percentages compared with fish fed the MFO diet. Whole‐body fatty acid percentages also varied among fish fed VO diets. Despite similar 18:2n‐6 and 20:4n‐6 percentages in the VO diets, fish fed diet CO contained significantly lower 18:2n‐6 proportions and significantly higher 20:4n‐6 proportions compared with fish fed other VO diets. Results of this study suggest dietary fish oil is not required for short‐term rearing of bull trout.