Sissel Susort believes levels of EPA and DHA are higher in Norwegian salmon than the Stirling research suggests. Photo: Linn Therese Skår Hosteland

Omega-3 research questioned

New research into the declining levels of key omega-3s in salmon has been questioned by a leading feed manufacturer. 

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Recent research from Stirling's Institute of Aquaculture revealed historically low levels of the long chain omega-3 fatty acids EPA and DHA in Norwegian farmed salmon, but the methodology behind this research has been questioned.

“We cannot quite understand how they arrived at these figures,” Sissel Susort, Skretting’s global product manager for grower feeds, told kyst.no

According to the Scottish research, the average level of EPA and DHA in Scottish farmed salmon fell from 3g per 100g in 2006 to 1.37g per 100g in 2016. They also found that the content of farmed salmon Faroese now averages at 1.03 grams per 100g and that Norwegian farmed salmon has only 0.81 grams per 100g.

Susort says that Skretting has almost 20 years of data on levels of EPA and DHA in Norwegian farmed salmon fed on the company’s diets and does not recognize the findings.

“We have kept a close eye on developments over the years, and levels have indeed fallen slightly,” admits Susort, “but we have never seen as low levels as suggested by Stirling. In our experience, the levels are not representative of Norwegian farmed salmon, and the level is considerably higher.”

Skretting is the largest supplier of feeds for Norway’s seawater sites and, according to the company's data, they have never measured levels below 1.2g per 100g salmon.

“On our last quarterly statistics show that large Norwegian farmed salmon fed on Skretting feed contained 1.7g per 100g on average,” she says.

Research methods

She wonders if the Stirling data was built around analysing smaller salmon, or a part of the fish other than the fillet – such as the tail – which contains lower levels of EPA and DHA.

“In a large salmon the fat content is about 17-18%, while it is around 14% in a smaller one. If you do some quick calculations, this can have a major impact on the result,” she explains.

“In addition, the fat content depends on the part of the fish that is tested. The highest fat content is in the abdomen, while it is lower in the back and towards the tail,” she adds.

She points to recent research by NIFES, which found that a portion of 150g of farmed Norwegian salmon contained 1.9g of EPA and DHA (equivalent to 1.3g per 100g) as well as 1.3g of plant omega-3s.

Regional differences

Stirling’s findings that Scottish and Faroese salmon contain more EPA and DHA than Norwegian farmed fish does not, however, surprise Susort.

“Scotland, in particular, and the Faroe Islands, to a lesser extent, have done less to cut down on fish oil content in feeds. The market in Scotland has largely been driven by supermarket standards that have their own requirements for fatty acids contents,” she says.

“However, I do not believe they are so high above Norway and the Faroe Islands as Stirling’s research suggests,” Susort adds.

She also argues that it is very important that the Norwegians use less fish oil in their feeds.

“Because Norway’s salmon production industry is so large, it has had to take responsibility for cutting down on fish oil. Due to raw material supply, this has been absolutely necessary to produce a growing volume of salmon in a sustainable way in the past 10-15 years,” she points out.

Looking ahead, however, she is aware that the industry will have new sources of marine omega-3s to draw on.

“By adopting algal omega-3s as raw materials, farmers will be able to decide how much of these fatty acids they want to have in their salmon but, at the moment, customers need to pay a fair amount extra for high omega-3 content,” she concludes.