Effects of dietary lipid substitution on swimming performance during the early developmental stages of Chinook salmon (Oncorhynchus tshawytscha)

The marine fish oils present in farm feed not only comprise a substantial proportion of the cost of aquacultural salmon production, they are also responsible for the accumulation of anthropogenic contaminants in the fish, such as PCBs and dioxins. Our study looks to assess the practicality of substituting these marine fish oils with canola oil, a vegetablederivative which has the potential to decrease feed costs in salmon production, as well as reduce levels of harmful contaminants present in the fish. Over seven months, four groups of Chinook salmon (Oncorhynchus tshawytscha) were fed one of four diets differing in their respective canola oil/anchovy oil ratios (0/100, 25/75, 50/50, and 75/25 total lipid content). These ratios, as well as the feeding of the fish earlier in development, was to supplement a previous study investigating the effects of dietary lipids on fish physiology so as to further investigate the effects of canola oil replacement. Swimming performance was measured for the fish of each group through the determination of their critical swimming velocity (Ucrit), and from these values the overall physical condition of the fish could be inferred. Upon fatiguing, other indicators of osmoregulatory stress were measured in the fish, including gill Na+/K+ ATPase activity and morphology, plasma osmolarity, Na+, Cl, and muscle water content. No significant differences between the diets have been found regarding the fishes’ swimming performance or muscle water content, suggesting canola oil as a viable substitute for anchovy oil in Chinook salmon