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What we did: We modified the dietary fat portion of farmed salmon food by replacing the traditional anchovy oil and poultry fat with canola oil. We reared Chinook salmon on this food for up to 40 weeks, and then investigated how the plant-based lipids impacted the physiology and fatty acid profiles of the fish.
What we found: Canola oil substitution had no effect on the swimming performance, metabolic rate or hypoxia tolerance of the salmon. Though the whole body fatty acid profiles of the fish were altered by diet, the polar lipids that comprise the cellular lipid membranes were not, and this is what likely explains the lack of physiological effects.
What this means: The typical fish-derived oils that comprise the lipid portion of farmed fish food are expensive and unsustainable, requiring roughly three fish to feed each farmed fish. Our results, which compliment those of a companion study that observed no adverse effects of canola oil substitution on fish growth, survival, feed intake and conversion, or ionoregulatory process, point to canola oil as a cheap and sustainable way to supply farmed fish with lipids.