Feeding fish diets with fishmeal and fish oil partially replaced by plant and/or animal sources can mean both lower levels of organic pollutants in the fish and lower production costs.
This was the hypothesis Dr. Erin Friesen, Product Manager at Skretting North America, decided to pursue when she started her PhD research in Food Science in 2003 at UBC.
In order to meet consumer demands for fish products, the aquaculture industry is growing at a rate of approximately eight percent per year. This in combination with a worldwide commercial fishery that isn’t seeing growth in the amount of fish it catches, suggests that the worldwide demand for fish oil will soon exceed supply, said Erin.
This is where suitable alternative feed ingredients of plant and/or animal origin become imperative, she added.
Farmed fish have often come under attack for containing higher levels of persistent organic pollutants (POPs) such as polychlorinated biphenyls, dioxins, furans and flame-retardants. The major sources of theses POPs in farmed fish are the fish oil and to a lesser extent, fish meal, in the feed. As a result, in addition to lowering production costs, the use of plant and/or animal ingredients has the potential to lower levels of POPs found in fish flesh.
Erin’s research co-authored with researchers at the Department of Fisheries and Oceans included both tank feeding trials with Atlantic salmon and sablefish and an on-farm field study in 2005 with commercial farmed salmon. She examined the effects of partially replacing marine fish oil in aquaculture feeds with economical and abundant oils from land-based sources such as flax oil and canola oil. In the laboratory feeding trials, decreases in contaminants were found to be directly related to how much marine fish oil was replaced with alternative oil sources.
For the farm site feeding trial, fish were collected from various BC farms in both 2003 and 2005. In 2003 farms were using higher levels of fishmeal and fish oil in their diets and in 2005 the diets were more highly replaced with alternative sources of protein and fat.
“The more knowledge (we) have on replacements, the better”, Erin stated.
The findings from this study showed that with more replaced diets, the contaminant levels in farmed Atlantic salmon were similar or lower than wild Pacific salmon but at the same time had higher flesh levels of Omega-3 fatty acids than wild salmon. Consumption of both farmed Atlantic salmon or wild Pacific salmon can meet recommended weekly Omega-3 nutritional requirements.
Although Omega-3s are needed by the body for optimal memory and performance, our bodies can’t produce them naturally. So that means we must regularly eat foods that contain them. This is where fish comes in, with its significant levels of this necessary healthy fat.
Erin’s research findings have been published in the journal Environmental Science and Technology.