A swimmer's diet: substituting dietary lipids and the resulting effects on swimming performance in Chinook salmon (Oncorhynchus tshawytscha)

Temperate-water marine fish provide the best dietary source for omega-3 (n-3) highly unsaturated fatty acids (HUFAs). Wild marine fish stocks are drastically declining worldwide; aquaculture industries are expanding, but because wild marine fish oil is still the primary lipid component of commercial feed, efforts to find alternate lipid sources (e.g. plant source HUFAs) are becoming increasingly important. Canola oil (n-6 HUFA) was chosen for this investigation. Six experimental diets were developed and tested on juvenile Chinook salmon (Oncorhynchus tshawytscha), wet weight ranging 11 g start to 70 g finish, over a 20-week period. Proximate composition of each diet was maintained, but various ratios (50, 40, 30, 20, 10, and 0%) of anchovy oil were substituted with canola oil. Every four weeks, maximal aerobic swimming velocity (Ucrit) was determined and repeated after a one hour recovery, as an overall indicator of physical status. Ucrits, recovery ratios, and hematalogical parameters were calculated but not found to significantly differ in fish between diet types, across all four months, and between freshwater and seawater swims. These data indicate that supplemental dietary lipid sources may consist of up to 50% canola oil without affecting swimming performance in juvenile Chinook salmon. The lack of difference is interesting in light of recent studies demonstrating effects of supplemental lipids on respiratory and cardiac physiology in other species. Our observations may indicate that altering 50% of the total dietary lipid is not enough to alter physical performance; additionally, our results may be species-specific or coupled to the developmental stage of the organism.