Salmon farming in Scotland

Salmon farming has been big business in Scotland since the 1980s. Photo: Adrian Warren and Dae Sasitorn,

Lisa Duchene writes in Global Aquaculture Advocate about a recent study by Stirling University (Scotland) researchers (on the Impact of sustainable feeds on omega-3 long chain fatty acid levels in farmed Atlantic salmon, 2006-2015, Scientific Reports) that revealed that the amount of omega-3 fatty acid in farmed salmon in the UK has decreased by 50% in the past 10 years.

As the salmon aquaculture industry expanded to four continents in recent decades, a reality about the product’s primary input – feed, largely derived from wild fisheries in the industry’s earlier days – became clear to producers: Feed required supplementation, via terrestrial agriculture, to reduce dependency on finite marine resources, i.e. fishmeal and fish oil.

But with the inclusion of more terrestrial plant ingredients (soy, rapeseed oil and other ingredients that do not contain similarly high levels of healthful fatty acids) came another reality: The nutritional profile of the farmed fish would inevitably change as well. Research from the University of Stirling, originally published in February, confirmed this, and even put a number on the decline: Farmed salmon from Scotland, on average, have about half the levels of omega-3s that they once did.

“So, as the aquaculture industry continues to grow, the finite amount of fish oil is being spread thinner and thinner and combined with vegetable oils in the feeds of fish, resulting in a decrease in the levels of omega-3s in farmed salmon,” said Matthew Sprague one of the researchers.

“The EPA+DHA of salmon farmed in the UK is largely dictated by the retailers themselves, and so it is a very bespoke product. So there are some salmon producers who use higher levels of fish oil in the diets,” he said.

One such producer, Loch Duart Ltd., which farms in northwest Scotland, responded shortly after the BBC News report was published that the omega-3 levels in its fish remain high, at 2.7 g EPA+DHA per 130-gram portion, or 90 percent of the weekly recommended requirement of 3 grams EPA+DHA. “Our feed policy – low-density rearing, fallowing, and other environmentally friendly practices – make Loch Duart salmon a little more expensive and we think it is worth it,” the company stated in its response.

The researchers also commended the aquaculture industry for helping to investigate alternative future sources of omega-3s.

“The likely contenders [are] microalgae and transgenic plant sources,” Dr. Sprague said. “These have been investigated for some time now, but take time to come to fruition to supply the levels that aquaculture requires.”

AlgaPrime™ DHA, an omega-3-rich whole algae ingredient developed by TerraVia in partnership with Bunge Ltd. has recently entered the feed market as an alternative to ingredients like fish oil and fishmeal. According to the company, “AlgaPrime DHA can ease the industry’s reliance on wild fish capture and help preserve the marine environment while providing a sustainable, scalable and economically viable source of omega-3s.”

The feed product is currently being made at TerraVia and Bunge’s SB Renewable Oils joint venture facility in Brazil. “Using AlgaPrime DHA could help arrest and reverse the decline in omega-3s in farmed salmon,” said Dr. Walter Rakitsky, Senior Vice President, Emerging Business, at TerraVia. “AlgaPrime DHA contains approximately three times the level of DHA compared to fish oil. One ton of AlgaPrime DHA is the equivalent of saving up to 40 tons of wild caught fish from our oceans on a DHA basis.”

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