Salmon, like humans, require omega-3 fatty acids in their diet to function healthily. But as the fish farming industry expands, feeding salmon and other aquatic species with pellets containing fishmeal and oil derived from processing wild-caught marine fish is unsustainable in the long term. This is due to rising demands for these commodities for aquafeeds and other purposes in the face of finite or declining annual global fish catches.
To provide a solution with respect to fish oil, a team of scientists from the University of British Columbia and the Department of Fisheries and Oceans, Canada, have been studying the effects of replacing anchovy oil with canola oil (also known as rapeseed oil) in the diets of salmon.
The research group, led by Professors Colin Brauner and Patricia Schulte in collaboration with Dr. Dave Higgs in the Department of Fisheries and Oceans Canada, has been monitoring changes in fish growth, exercise capacity and hypoxia tolerance to investigate whether there are any negative consequences on the fish's growth performance and health from a change in diet. Their results, to be presented at the Society for Experimental Biology Annual Meeting on Tuesday 4th April [session A4], find that the fish suffer no ill effects from replacing up to 75% of the dietary lipid (mainly from fish oil) with canola oil.
"We are finding that as long as we meet the basic essential omega-3 fatty acid needs of the salmon with some dietary fish oil, such as those for EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), the fish can be reared successfully on these alternate diets", says Professor Brauner, "As aquaculture continues to expand, fish oil will become increasingly more expensive because it is a limited resource, and canola oil will not only be more sustainable as a lipid source, but also will be consistently more cost effective too".
Using canola oil instead of marine fish oil (e.g. anchovy oil) in fish feed will also reduce the accumulation of contaminants in salmon such as PCBs and dioxins that are present in wild marine fish. This new "vegetarian" dietary approach is increasingly being adopted and will likely be applied to many other cultured fish species in the future.
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