Reports of falling levels of omega-3 fatty acids in farmed salmon have sparked a debate in the United Kingdom over the use of vegetarian fish feeds that are blamed for the phenomenon.
A prime-time news report by the BBC on 6 October cited a study by University of Stirling, which has one of the top-ranked aquaculture research departments in the world, claiming that levels of omega-3s in farmed salmon have been halved over the past five years.
The study, which was led by Professor Douglas Tocher, found that omega-3 levels have fallen in farmed salmon as feed manufacturers have switched from using fish feeds made with oily fish such as anchovy and sardines to feed made from soy and other alternatives in response to concerns from environmentalists.
"About five years ago, a portion of Atlantic salmon of 130 grams was able to deliver 3.5 grams of beneficial omega-3s. This is actually our weekly recommended intake. Now, the level of omega-3s has halved. Therefore, instead of eating one portion of farmed salmon, we would need to eat two portions," Tocher said.
Even with the reduced amount of omega-3 fatty acids in farmed salmon, it remains one of the richest food sources for the consumption of the oil, which is widely considered by nutritionists to be an important part of a healthy diet. In the report, Tocher stressed that farmed salmon was still one of the richest sources of beneficial fish oils and he urged people who buy farmed salmon for its potential health benefits to continue doing so.
Tocher’s colleague, Matthew Sprague, has stated that in light of the new data, the U.K. government should consider changing its advice to consumers. Currently, the government recommends the consumption of two portions of fish a week, one of which should be an oily fish. With the newly revised data, Sprague said he thinks that figure should be upped to two portions of oily fish per week.
Alison Tedstone, chief nutritionist at Public Health England, said that ultimately everyone should eat more oily fish. Currently, the average weekly consumption is only 54 grams of oily fish, though the government’s official recommendation is at least 140 grams.
The University of Stirling study has also launched some soul-searching amongst aqua-feed companies, who have spent years pouring resources into developing alternatives to traditional feeds using small oily fish, which have, as a result, become overfished in many parts of the world. Commercial alternatives either available on the market or under development include feeds made using insect meal, and feather and bone meal, but while these may help to reduce the level of protein used in fishmeal, they do little to nothing to boost omega-3 levels.
With the renewed focus on the retention of omega-3s, Skretting, the first aquaculture feed company to develop commercial salmon feed formulations that were completely fishmeal-free, recently announced a breakthrough using marine algal oil. Skretting is now in trials with a product containing marine algal oil produced by natural algae from the ocean and cultivated in land-based facilities. This reportedly has unprecedented levels of EPA + DHA (key components of omega-3 fatty acids), thanks to a joint development by global science-based company Royal DSM and specialty chemicals company Evonik. The product is currently approved for use in Europe.
In the United States, TerraVia and Bunge Limited have also developed a whole algae specialty feed for aquaculture. The product, called AlgaPrime, is made at a facility in Brazil using sugarcane waste material as a feedstock for the algae.
“[AlgaPrime] could be a real game-changer in keeping our oceans healthy by offering a non-marine based, sustainable source of omega-3s to help address the growing ‘fish in, fish out’ problem today,” TerraVia CEO Jonathan Wolfson said. “It provides a far more sustainable non-fish based source of DHA to help maintain healthy oceans while improving the nutritional value of seafood for our families.”
Following the BBC news report, independent Scottish salmon company Loch Duart was quick to reassure consumers that levels of omega-3s remain high in their salmon. The company feeds its fish a bespoke diet composed of fishmeal created from the by-product of the Icelandic capelin fishery.
“Our results are considerably higher than the stated average for farmed salmon in the BBC report,” said Loch Duart Sales Director Andy Bing.
Another solution to the omega-3 quandary is the use of genetically modified (GM) rapeseed oils plants that have been altered to produce fish oils. Professor Jonathan Napier of Rothamsted Research in Harpenden, U.K., has developed the product and is currently in field trials with it.
“We think GM technology has the potential to help fish farming become more sustainable and continue to grow as an industry,” he said.
However, whilst GM products are widely produced in the U.S. and Asia, they are not currently accepted by consumers in Europe.
The search for new sources must therefore continue, but feed scientists are confident that more breakthroughs lie just around the corner.