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Can we have our farmed salmon and eat it too?

September 19, 2019
Christina O'Sullivan

Christina O’Sullivan is the Campaign & Communications Manager at Feedback, where she manages the ‘Fishy Business’ campaign. Feedback is a campaign group working to regenerate nature by transforming the food system. Christina has an MSc in Food Policy from the Centre for Food Policy, City University. She has worked at the Cornell Food and Brand Lab and the Global Centre for Food Systems Innovation at Michigan State University.

What do farmed salmon eat? If you’re anything like me before I started working on this campaign, you probably find it difficult to answer that question. While feed for terrestrial animals has come under a lot of scrutiny recently, aquaculture (fish farming) has largely swum under the radar. To find out more, Feedback recently published the first report of our Fishy Business campaign, which investigates the natural resources – in particular wild caught fish – which underpin the Scottish farmed salmon industry and the implications for the industry’s sustainability.

While 40 years ago aquaculture provided 5% of the world’s seafood, as the fastest-growing sector of the food system, it now accounts for approximately half the world’s seafood consumption, with further projections for large-scale future growth. Around 60% of the world’s salmon production is farmed, and in Scotland this figure reaches 100%, with the last commercial wild salmon fishery closing in late 2018.

In Scotland, salmon farming has grown from what was once a relatively small industry in the 1970s to being the UK’s largest food export today. Having grown by over 90% between 1997 and 2017, the industry association, the Scottish Salmon Producer’s Organisation, has set out a target to expand by a further 100-165% by 2030 (from a 2018 baseline). This expansion is already underway, with ‘supersized’ (greater than the current limit of 2,500 tonnes of fish per farm) salmon farms located in deep water locations given the go-ahead by the Scottish regulator SEPA in June 2019.

What’s wild fish got to do with it?

What we feed to the animals we eat is a question central to the current and future sustainability of the global food system. I stopped eating meat primarily for environmental reasons – the level of feed required to satisfy the livestock industry is, in my view, inefficient and wasteful. Diverting good food that could feed people to animals does not make sense, especially in the context of the climate crisis. Unfortunately, the farmed salmon industry faces a similar issue.

Farming fish at an industrial scale requires industrial quantities of feed: the key feed inputs for salmon aquaculture are sourced primarily from global wild fisheries and land-based agriculture. As to the former, inputs include fish oil and fishmeal made from wild-caught ‘forage fish’ – small oceanic fish from fisheries all over the world. These fish play a critical role in moving nutrients through the food chain by eating plankton and in turn nourishing marine animals higher up in the ecosystem, such as larger fish and seabirds. Moreover, research shows that 90% of fish used in fishmeal and oil production comes from food-grade or prime food-grade fish – in other words, fish which in theory could be eaten by people. Regarding land-based inputs, salmon feed also contains other edible ingredients such as soya and corn, with recent reports finding that farmers in Norfolk are now growing beans to feed Scottish salmon.

In 2017, the Scottish salmon industry produced 189,707 tonnes of salmon (around 42 million fish). We calculated, based on industry production data, that to double in size by 2030 the Scottish industry would require a massive 310,000 tonnes of extra wild fish a year, assuming the current feed mix. For context, the current quantity of wild fish fed to farmed Scottish salmon, 460,000 tonnes, is roughly equivalent to the amount of seafood (both wild and farmed) purchased by the entire UK population. Where and how this extra wild fish will be sustainably sourced is an unanswered question.

The industry presents two key defences of its reliance on wild fish. The first is that the forage fish used in fishmeal and fish oil are sustainably fished, and are not generally wanted or eaten by people, so there is no danger of exacerbating feed-food competition. The second is that the fishmeal and oil used in aquaculture are largely ‘by-products’ of resources used in other industries, such as pig and chicken feed. We have concerns about these arguments, which I have set out below.

“Unmarketable” fish?

The industry uses the terms “unmarketable fish” or “low consumer preference fish” to describe certain marine ingredients in feed. What does “unmarketable” mean in relation to fish suitable for human consumption? Fundamentally this question comes down to how we believe consumer demand is shaped. We know that new or revived markets for human consumption are being found for many former reduction species, such as capelin, Atlantic and Pacific herring. Salmon itself has benefited massively from marketing-based on health claims. Data from Defra shows that purchases of salmon have risen by 550% since 1974. Emma Jayne Abbots, lecturer in social and cultural anthropology and heritage at University of Wales Trinity St Davids, commented "I think health marketing around the benefits of omega 3 as well as the decline in price explains the increase in salmon consumption."

Therefore, while it may be convenient for the food industry to claim that there is no market for forage fish, the reality is that consumer food preferences are to a large extent shaped by the businesses that produce our food. As another example, monkfish used to be considered a fish for the poor and was banned from some markets in France because of its appearance, but now it is trendy and expensive.

The link between farmed salmon and intensive livestock

The salmon industry claims to produce protein that is sustainable compared to meat, as salmon has a lower feed conversion ratio and thus requires less feed per kilogram of product. However, the world of farmed salmon is intrinsically linked to the livestock industry.

The salmon industry argues that the feed conversion ratio of salmon farming is lower than it might appear at first glance, because fishmeal left over from the production of the large quantities of fish oil consumed by the industry do not go to waste – rather, that leftover fishmeal is used in other industries. According to the Marine Ingredients Organisation, using an approach that accounts for these market efficiencies means that, on average, 0.82 kilogram of wild-caught fish is needed to produce 1 kilogram of salmon. However, this also means that if market demand for this leftover fishmeal were to decrease and that fishmeal ultimately became wasted, then then farmed salmon’s feed conversion ratio would increase significantly.

This means that the salmon industry is symbiotic with other industries that have a high environmental footprint, such as shrimp and pig production. Essentially, the farmed salmon industry can only claim efficiency by supplying the leftover fishmeal from the fish oil it requires to inefficient methods of food production, thus making it intrinsically linked to those industries while simultaneously claiming to be more sustainable than them.

Taking a global food security perspective

The industry claims that salmon is a net producer of protein but, as highlighted in the above section, there are issues with the justification of that claim. However, even if farmed salmon were a net producer of protein, it is vital to consider who is consuming it. In addition to being sold by retailers and in restaurants around the UK, salmon exports from Scotland in 2017 were valued at a record £600 million, the USA is the biggest market for Scottish salmon with sales totalling 193 million pounds, followed by France (188 million pounds). Reports have shown that the growing aquaculture industry and the simultaneous need for more fishmeal and fish oil has led to food security problems in places such as West Africa. We may be removing a vital protein source from people who rely on it, so that people in high income countries such as the US, who generally already consume too much protein, can eat salmon.


Our research shows that the Scottish salmon industry uses billions of fish caught from delicate wild ocean ecosystems, where they play a crucial role in the wild food chain – fish that, in many cases, could be eaten by people. The salmon industry has yet to set out how it will reconcile its expansion plans with sourcing its feed inputs sustainably. Read the full report here: Fishy Business: The Scottish salmon industry’s hidden appetite for wild fish and land.



Angela Druckman's picture
Submitted by Angela Druckman (not verified) on

This article is interesting and a pleasure to read. However, it omits discussion of the growing trend to feed insect protein to fish such as salmon. Insect protien (for example, black soldier fly) is a more sustainable feed.

Richard Newton's picture
Submitted by Richard Newton (not verified) on

There is quite a lot of conflation in this. Yes, fish production is now over 50% from aquaculture, but 7 of the top 10 species cultured are carps with low feed inputs and very low marine ingredient inclusions. These species support food security in some of the poorest nations. Salmon accounts for around 5% of world aquaculture. It now has around 12% fishmeal in the diet. The figures on sourcing are a bit skewed in my opinion. The marine ingredients fisheries that support salmon farming are well regulated and have some of the highest scores of sustainability from the Sustainable Fisheries Partnership. Over a third of fishmeal and oil is rendered from the by-products of fish processing; guts, heads, trimmings etc and there is significant scope for more as so much processing by-product is wasted. These resources should be better utilised before you look at trying to feed insects on feed grade substrates to produce insect meal inefficiently and expensively. Before you target the aquaculture industry, which is one of the most efficient ways of producing animal protein in food insecure nations, perhaps we should look at the amount of prime fish that goes to pet food?

Blake Lee-Harwood's picture
Submitted by Blake Lee-Harwood (not verified) on

I have a lot of sympathy with many arguments in this blog but some of them seem incorrect or potentially misleading. The fishmeal/oil industry does not prevent food grade fish from going for direct human consumption, it is simply a question of consumer preference and market forces. If there really is a huge market for capelin for diret hman consumption (which I doubt given the nature of the fishery) then it will easily command higher proces than the fishmeal industry can pay and product will naturally flow to consumers. The Peruvian government has spent decades trying to persuade its citizens to eat anchovies but with only very limited success and 5 million tonnes of the fish go to fishmeal/oil every year - there's literally nothig stopping this fish going into human food chains except the fact that they are not very palatable or easy to use. The point about the risks to food security from fishing for fishmeal/oil are well made but there are few well-substantiated cases (I have spent 8 years looking) and very little (if any) of the product from West Africa goes to salmon, it is almost all sent to China via processing plants in Senegal, Mauritania, Gambia and Morocco.

Dave's picture
Submitted by Dave (not verified) on

Wild salmon stocks have plummeted across the globe. Atlantic salmon have now reached endangered levels in many rivers across the UK. Many in Scotland blame fish farming, as the fish farms bring huge numbers of sea lice which decimate wild fish on their journey to and from spawning grounds. Having seen salmon farms in Shetland and elsewhere, I also tend to think of farmed salmon  as the factory farmed chicken of the seas. Farmed salmon are kept in similarly inhumane conditions. All reasons why I avoid eating salmon at all.

David Finlay's picture
Submitted by David Finlay (not verified) on

“Until the seas run dry: how industrial aquaculture is plundering the oceans”, published by the Changing Markets Foundation and Compassion in World Farming, reviews the latest scientific research on the impact of reduction fisheries (where wild fish are turned into FMFO), and the lack of transparency and sustainability ... April 2019

Christina O'Sullivan's picture
Submitted by Christina O'Sullivan (not verified) on

Thank you everyone for taking the time to read this blog and engage in a thoughtful way. I have responded to the comments below;

Angela Druckman: The Scottish government is looking at insects as an alternative; However, the Scottish farmed salmon industry appears wedded to maintaining a certain level of marine ingredients in their feed, which they market as a mark of quality. An additional challenge is that insects can’t entirely substitute fish oil, and it is the oil that is the biggest problem in terms of the fish in fish out ratio.

Richard Newton: Our works focuses specifically on the Scottish farmed salmon industry against the backdrop of the rapidly growing global aquaculture industry. The use of by-products was accounted for in our workings. ‘The marine ingredients fisheries that support salmon farming are well regulated and have some of the highest scores of sustainability from the Sustainable Fisheries Partnership.’; currently there is not enough transparent information to support this claim – with many of the key players in Scotland refusing to provide basic information on the composition of their feed and where it is sourced. Moreover, in the context of 33% of global fish stocks already being overfished and 60% are maximally sustainably fished, it forces the question is farming salmon the best use of the oceans ever declining natural resources. From a food security perspective, as highlighted in the piece, it is vital to consider who is consuming farmed salmon. In addition to being sold by retailers and in restaurants around the UK, salmon exports from Scotland in 2017 were valued at a record £600 million, the USA is the biggest market for Scottish salmon with sales totalling 193 million pounds, followed by France (188 million pounds). Reports have shown that the growing aquaculture industry and the simultaneous need for more fishmeal and fish oil has led to food security problems in places such as West Africa. On carp; Freshwater aquaculture of species such as carp carries environmental problems, including water pollution (Poore and Nemecek 2018) and greenhouse gas emissions (Robb et al. 2017). Freshwater aquaculture ponds create up to 450 grams of methane per kilogram of liveweight - for context, enteric fermentation in dairy cows creates 30 to 400 grams of methane per kilogram of liveweight (Poore and Nemecek 2018). In other words, the worst types of freshwater aquaculture ponds emit more methane, a very powerful greenhouse gas, than dairy cows (Poore and Nemecek 2018).

Blake Lee-Harwood: This debate is essentially about how one believes consumer preference is shaped; data from Defra shows that purchases of salmon have risen by 550% since 1974 – it seems unlikely that this happened organically. In the UK context, considering that 98% of shoppers say they have used a supermarket for some of their grocery shopping every month it follows that supermarkets have a large role in what fish we buy. To highlight that a lot of the fish fed to farmed salmon could be consumed directly. We hosted an event with Michelin star chef Merlin- Labron Johnson, you can view a video from the event here: Regarding fishmeal and fish oil from West Africa, Mowi’s annual reports show they import from Mauritania and Morocco.

Dave: Thanks for your comment and everything you are doing.

David Finlay: Thanks for sharing. We are aware of this report and have worked with both Changing markets and Compassion in World Farming for our campaign.

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