Cut ‘wasteful’ Scottish farmed salmon and eat a more diverse range of fish for a sustainable seafood diet

25th Jun 20 by Jessica Sinclair Taylor

Farmed salmon industry challenged to overhaul feed practices to protect wild fish

Full reports:

Off the Menu: The Scottish salmon industry’s failure to deliver sustainable nutrition

On the Hook: Certification’s failure to protect wild fish populations from the appetite of the Scottish salmon industry

  • Every year the Scottish farmed salmon industry uses around 460,000 tonnes of wild fish to make fish oil to feed to farmed salmon, resulting in around 179,000 tonnes of farmed salmon.
  • Feedback have calculated that if we ate some of these wild fish directly, and cut our consumption of salmon significantly, we could access the same level of omega 3 as is currently delivered by Scottish salmon farming, while leaving 59% of wild fish – around 273k tonnes – currently caught for feed in the sea.
  • Salmon farming in Scotland suffers from high mortality rates – in 2019, the farmed salmon that died before being harvested led to a waste of around 25,000 tonnes of wild fish in the form of feed, enough to feed 2 million people their weekly portion of oily fish for a year.
  • If we added some farmed mussels to our diets, we could leave up to 77% of wild fish – around 354k tonnes – currently caught for salmon feed in the sea.

New research has shown we could eat a healthy diet and leave more wild fish in the sea if we ate a wider range of wild fish, and less farmed salmon. With NHS dietary guidelines encouraging UK citizens to eat at least two portions of fish a week, farmed salmon is often perceived as both a healthy choice, due to its high omega 3 content, and an option that relieves pressure on wild fish populations. But new modelling has shown that to access the same level of omega 3 and other micronutrients currently produced by the Scottish salmon farming industry, we should eat a lot less salmon, and more of a diverse range of wild fish, including sardines, anchovies and sprat[i]. By doing so we could leave 59% of fish currently caught to feed farmed salmon in the sea, helping to protect wild fish populations and ocean ecosystems.

Farmed salmon is popular: it is the most purchased seafood in UK supermarkets[ii], and Scottish farmed salmon is one of the UK’s top food exports by value[iii]. But farmed salmon’s omega 3 content is largely delivered by the inclusion of wild fish in its feed in the form of fish oil: previously, Feedback calculated that the Scottish salmon industry uses around 460,000 tonnes of wild fish a year for this purpose, roughly equivalent to the quantity of seafood purchased by UK adults every year – and roughly 90% of these fish could be eaten by people.

New modelling has shown that if we made more the wild fish currently used to feed farmed salmon, including herring, anchovies and sardines, alongside a smaller quantity of farmed salmon, we could leave 273,000 tonnes of wild fish currently used by the Scottish salmon industry in the sea.  If we added farmed mussels to our diet, which do not need feed and which contain high levels of micronutrients, we could leave 77% of wild fish caught for salmon feed in the sea, or around 354,000 tonnes.

Carina Millstone, Executive Director at Feedback said:

“While the Scottish farmed salmon industry may cultivate a reputation for clean and green nutrition, our evidence shows that producing farmed salmon is actually creating a wasteful and unnecessary burden on our oceans: this industry is more about corporate profit than it is about healthy and sustainable food. Delicious smaller fish such as herring, anchovies and sprat are full of omega 3s and deserve a bigger place on our menu, as do superfoods like farmed mussels, which do not rely on fish from fragile ecosystems for feed, and yet are hugely nutritious.

“Catching and producing ‘super’ seafood could be the basis of a new blue economy for the UK, and government, supermarkets and chefs can do much to promote truly sustainable fishing and aquaculture. Meanwhile, if the Scottish salmon industry is serious about protecting the health of our oceans, it should stop catching wild fish for its feed.”

The modelling shows that eating a small amount of farmed salmon could be environmentally sound as well as nutritionally beneficial, so long as the fish oil it is fed is solely made from by-products, such as heads and bones, of fish caught for human consumption. Currently the industry makes around one third of its fish oil from by-products.

In addition to making poor use of the micronutrients in wild fish, the farmed salmon industry’s production methods are highly wasteful. In 2019, around 5.8 million salmon mortalities were reported by the Scottish industry, roughly 14% of total production. This compares with a 5% maximum mortality rate for chicken farms qualifying for the UK’s Red Tractor scheme. Feedback calculates that feeding salmon that died during production in 2019 would have wasted around 25,000 tonnes of wild fish: enough to feed 2 million people their portion of oily fish per week for a year.

Feedback also argued that certification of wild fish used in salmon feed did not act as a guarantee of sustainability, based on data provided by the Scottish industry. Out of six companies operating at scale in Scotland, three responded to Feedback’s requests for transparency on feed: Grieg Seafood, MOWI and Loch Duart. Three companies, The Scottish Salmon Company, Scottish Sea Farms and Cooke Aquaculture did not respond[iv]. The data provided by the companies demonstrated a heavy reliance on certification to try to ensure sustainably sourced wild fish.

Dr Karen Luyckx, Head of Research at Feedback, said:

“There is strong academic evidence that certification is not a guarantee of sustainability, which is not surprising with such high demand for something that is in limited supply – but beyond this, the important question to ask is whether using wild fish to feed farmed fish, pets and other animals is a good use of the hugely important nutrients available in finite supply from our oceans. Our research concludes that it is not: at least as far as farmed salmon is concerned, it would be far better for our oceans and our health to consume some wild fish directly.”

Diversifying our seafood consumption could have considerable economic benefits. With the UK government promoting the consumption of wild fish from UK waters[v], including herring and similar ‘forage fish’ currently used to make salmon feed, there is an opportunity for fisheries authorities, chefs and retailers to promote the consumption of some of the smaller wild fish such as sprat and herring, which have become less commonly consumed in the UK.

As the UK government looks to provide further funding to the UK fishing and aquaculture industry[vi], and doubts raised about the economic contribution of salmon farming to remote coastal communities[vii], Feedback is calling for the government to support the development of low-impact, high nutrition alternatives to salmon farming, such as mussel and seaweed farming.


Methodology note on biomass, protein and micronutrients:

Farmed salmon producers argue that when looking at fish biomass, the amount of fish that goes into producing farmed salmon is equivalent to or less than the fish that comes out. This is based on the use of wild fish to make fishmeal and fish oil, with more fishmeal produced than fish oil per unit of wild fish processed. The salmon industry’s feed requirements, primarily the need to include a certain level of omega 3 in salmon diets, govern the level of fish oil needed in their salmon feed. This leaves a certain quantity of fishmeal ‘surplus’ to requirements for the salmon industry, and this can be used to feed farmed prawns, other fish such as carp, or livestock such as pigs. However, when we look at protein in salmon feed, rather than overall fish biomass, we see that farmed salmon are fed other protein ingredients, such as soy, which also has environmental impacts. When comparing all the protein in farmed salmon diets with the protein in the final salmon product, salmon are not efficient ‘converters’ of the nutrients in feed; for every 100g of protein that went in as feed, only 28g ends up on our plates  – it would be better to eat the protein in salmon diets ourselves. What salmon does provide, which other forms of protein do not, is micronutrients like omega 3. However, as this research shows, it is again more efficient and less of a burden on finite marine resources to eat a greater diversity of wild fish directly, than to access the nutrients in wild fish via farmed salmon. The only way that farmed salmon is an efficient vehicle to deliver micronutrients into our diets, is if the industry makes use of ‘by-products’ from fish caught for human consumption, which would otherwise go to waste, or be used for non-food purposes (such as chicken feed or pet food). The salmon industry makes around one third of the fish oil it needs from by-products: to operate within these limits it would therefore need to decrease current production of farmed salmon by two thirds. Other sources of by-products may be identified, however, these will need to be carefully monitored to ensure demand for fish oil does not create a perverse market incentive to drive additional fishing.




[iv] Feedback wrote to all six companies in July 2019 requesting transparency on sourcing of wild fish for feed, including locations of fisheries and types of fish used. Only Grieg Seafood and MOWI responded in any depth to these requests for transparency. See the full report for details:




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