We use cookies to allow us and selected partners to improve your experience and our advertising. By continuing to browse you consent to our use of cookies. You can understand more and change your cookies preferences here.

Home & garden.

Updated: 9 Nov 2021

How to buy sustainable fish

The sustainability issues with some of our favourite fish, plus better alternatives and the labels to look for
Olivia Howes
fish on fish counter in ice

Fish is high in protein, low in fat and, if it's oily, high in omega 3 and micronutrients. The NHS advises us to eat at least two portions of fish a week. 

But in the UK we can be unadventurous in our seafood choices; 80% of the fish we eat comes from just five species – cod, haddock, prawns, salmon and tuna. 

When we asked Which? members about their seafood habits, we found that 56% regularly bought salmon and 42% cod. Prawns, haddock and tuna follow behind. Mackerel and sea bass were the next most regularly bought, at 18% and 16% respectively.

Reliance on this small number of varieties places pressure on wild fish numbers or can lead to unsustainable farming practices. 

But there are more sustainable seafood choices out there. When we asked 1,246 Which? members, 77% said they’d be willing to alter their seafood consumption based on sustainability.

Video: What fish is sustainable?

Why do we need to change our seafood choices?

school of fish
The Marine Stewardship Council (MSC) says a third of global fish stocks are now fished beyond sustainable limits, impacting global food security. 

 Farmed fish account for more than half the fish consumed globally, and aquaculture, or fish farming, is sometimes seen as a more sustainable option. But it comes with its own environmental issues. Some farming methods have negative impacts on the environment, and carnivorous species such as salmon and prawns require wild-caught fish in their diet even if they themselves are farmed.

Losing species is about more than just loss of biodiversity. The ocean depends on resilient ecosystems to keep performing its role as a carbon sink (about a third of the carbon we create is stored in the ocean). And a recent study calculated that bottom trawling fishing methods could be disturbing up to one gigaton of carbon a year, more than (pre-pandemic) aviation emissions, although more research is needed.

What is being done to prevent overfishing?

As a general rule, smaller fishing boats often have environmental advantages over larger ones. 

Smaller, in-shore vessels tend to use passive fishing gear such as pots, traps and fixed nets with less environmental impact. Rather than stopping fishing altogether, one approach is to favour these low-impact methods and create strategically placed marine protected areas (MPAs), to safeguard sensitive habitats and breeding and nursery areas.

The aim, recently reiterated and supported by the G7 members, is to protect 30% of the world's oceans in MPAs or marine reserves by 2030. This is ambitious: currently only 6.35% of the ocean has been designated as a MPA, according to the International Union for the Conservation of Nature (IUCN). Only 1.89% of these are 'no take' MPAs, where no fishing or other extractive activities can take place.

Greenpeace is currently campaigning for a ban on supertrawlers being able to fish in UK MPAs. None of these vast vessels, over 100 metres long, are UK owned and yet they spent over five and a half thousand hours fishing in UK protected areas in the first six months of 2020.

fishing trawler

Sustainable seafood labels to look out for

What to look for on the label

If you are buying packaged, uncooked and unprocessed fish, information must be given about place and method of catch somewhere on the pack.

This isn't required for fish that has been processed, such as fishcakes or fish fingers.

Most UK supermarkets are signed up to the Sustainable Seafood Coalition which includes rules around labelling. The word ‘responsibly’ will either mean the product is farmed (farmed products can’t be ‘sustainable’) or from a wild source that has been risk assessed. 'Sustainably’ sourced means the fishery is accredited by an independent certification scheme.

Aquaculture Stewardship Council – ASC
ASC logo
An independent certification covering legal, environmental and social criteria. There are 11 different standards currently for 17 different species of fish, but an forthcoming update will create one aligned standard for aquaculture. 

This will incorporate fish welfare and a feed standard ensuring all feed mills that certified farms source from are producing responsibly, including ingredients including wild fish, soy and palm oil. 

Global G.A.P.

A business to business standard for the certification of agricultural goods which includes environmental care, welfare and workers’ health and safety. 

Global G.A.P. does also have a consumer label called the GGN.  Consumers can search a unique 13-digit number found on the packet on the GGN label portal to find a profile for the corresponding farm or business.

This packaging logo isn’t that widespread in the UK so fish may well be certified without consumers being aware - supermarket fish is often certified to this or the Global Aquaculture Alliance's BAP scheme.

Global Aquaculture Alliance – Best Aquaculture Practices (BAP)

The BAP logo is more common in the US. Standards cover environmental responsibility, animal health and welfare, food safety and social responsibility. 

Each stage of the production process (farms, processing plants, hatcheries and feed mills) must pass certification to achieve a star – ideally choose 4* certified products.

​Soil Association Organic

Soil association logo

Farmed seafood certified organic will generally have less environmental impact as fewer chemicals and medicines are allowed. Stocking densities tend to be lower, which the Soil Association says can reduce stress and the risk of disease and parasites. 

The first choice for feed is usually by-products of fish otherwise destined for human consumption and organic plant-based feed. Whole fish feed (wild fish) must be justified as necessary for fish health and welfare.  

There are other organic certification schemes such as Organic Farmers and Growers (OF&G).

Marine Stewardship Council – MSC

MSC logo

The MSC blue tick requires wild-caught fish to come from a fishery assessed as sustainable. This means only fishing from healthy stocks, keeping the stocks well-managed and minimising the impact of fishing on other species and the ecosystem. 

In 2019/20 MSC-labelled products accounted for over a third of UK seafood retail sales.  

While any size of fishery can be MSC-certified, costs and paperwork can be barriers to entry for smaller operations. Many UK fisheries are also ’data deficient’, meaning they don‘t have enough scientific information on fish populations and environmental impact to pass an assessment. 

The MSC facilitates Project UK – a partnership of UK fishery improvement projects to encourage sustainability of fisheries that aren’t yet certified.

Fish swaps

If you are prepared to broaden your culinary horizons, there are plenty of local seafood options you can choose to improve your eco-footprint while eating seafood. Sustain, an alliance for better food and farming, has more advice and information on its website, or keep reading for our recommended swaps.


The majority of salmon in the supermarkets will be Atlantic salmon and it will be farmed, mainly in Scotland. 

Issues with salmon farming highlighted by campaigners are around their feed, the pollution caused by their waste and pesticides, and the parasites they can spread, such as sea lice to local fish populations. 

The industry is working on innovations to improve the environmental impact of farms, but environmental campaigners, including the Marine Conservation Society, say planned expansion of the salmon farming industry needs to be paused until these issues are tackled.

All Scottish salmon is RSPCA-assured, a standard that ensures certain welfare requirements are met, incluing humane slaughter.

The best choice for farmed salmon, according to the Good Fish Guide, is ASC-certified salmon or organic. Organic salmon is fed largely on feed made from waste trimmings. In practice this means far less wild-capture fish is used. Organic farming can also help to mitigate against some of the environmental impacts.

Wild Pacific Sockeye Salmon is a good option, but avoid wild Atlantic salmon.

Swap for

UK rainbow trout are less intensively farmed and because they are farmed in ponds they tend to have less environmental impact than fish farmed in open net pens. They still need to be fed wild fish, though. Eating vegetarian fish such as tilapia removes this issue.

UK brown crab The Shellfish Association of Great Britain says 100g of crab contains 45% of your weekly amount of Omega-3. The most sustainable method of catch is through pot or creel, as this selects larger crabs and has minimal impact on the surrounding envrionment. 

Alternatively, get your omega-3 by eating what the salmon eats. Oily fish like herring, anchovy and sardines are high in micronutrients.

Warm water prawns or shrimp

Big tiger or jumbo prawns (also known as shrimp) are found in warm water and can be farmed, commonly in South-East Asia, or wild-caught. Wild-caught prawns are bottom trawled, which damages the seabed and can pick up huge amounts of marine creatures and fish caught unintentionally, known as bycatch.

Farmed prawns were historically associated with the destruction of mangrove forests. Studies have indicated mangrove forests can store four times as much carbon as tropical forests.  

Like salmon, prawns require fish protein in their feed and a proportion of this comes from wild-caught fish. 

Shrimp farms have also been associated with human rights abuses.

The Good Fish Guide says choose organic or ASC prawns. Part of the ASC standards include farms demonstrating they are treating workers fairly. 

Swap for

The best bet is to avoid warm-water prawns, opting instead for cold-water, wild-caught, MSC-certified prawns, typically from the waters between Canada and Norway. They are also harvested by bottom trawling, but in areas of muddy sediment, where the lasting environmental impact is lessened and bycatch is less of an issue.

Pot-caught UK langoustines are fished with very little impact on the environment and are part of a UK Fisheries Improvement Project (FIP). 

Rope farmed mussels have some seriously impressive sustainability credentials – they take their nutrients from the sea water and, at the same time, filter and clean it, actively sequester carbon into their shells, and are full of micronutrients and high levels of Omega-3. Rope farming means harvesting them does no damage to the sea bed.


Tuna is often fished in the High Seas, the international waters that make up around two-thirds of our oceans. Monitoring and controlling activities in these waters is challenging and the Environmental Justice Foundation and other campaigners have uncovered human rights abuses and slavery.

Some tuna is more sustainable than others. Skipjack and Albacore are usually the best choices but it does depend on fishing methods. Some brands and supermarkets will clearly label their tuna as caught by pole and line - this and troll fishing (another type of line fishing) are generally viewed as the most sustainable. 

Avoid tuna caught by gillnet as these nets can be up to 7km long and have high levels of bycatch.

Most Pacific or Southern Bluefin tuna stocks are at critical levels.

Swap for

UK mackerel is a good nutritional substitute when fished locally. All mackerel in the northeast Atlantic lost MSC certification in 2019 after stocks dropped below a precautionary level and country catch quotas were deemed too high. But UK mackerel, mainly from Cornwall, by boats using handlines is a good choice.

Sardines, another oily fish high in Omega-3, can also be fished locally. 


Cod was once the cautionary tale of overfishing – the 90s saw a collapse in Atlantic cod stocks. Impressive efforts to rebuild those stocks mean that you can now buy sustainable cod, but it's worth noting that this won't be from the UK – most of the MSC-certified cod you'll find in the supermarket comes from Iceland or Norway.

There are some good white fish alternatives that you can look out for.

Swap for

Hake can be fished sustainably from the UK.

Coley from Iceland and the North-East Arctic is also a good choice, and is often cheap to buy.

Pollock sustainability varies, but there are some good choices from Alaska and parts of Russia.

Or try haddock.


The UK's haddock stocks are in a reasonable state. Much of what’s in the supermarket will be MSC-certified.

Methods of catching haddock can mean there is some bycatch, so where it is fished can have an impact. The Cornwall Good Seafood Guide says you can protect juvenile fish by only buying fish that are larger than 30cm and avoiding buying fresh haddock during their main breeding season – March and April.

Swap for

You don’t need to avoid eating haddock. But hake, coley and pollock are good substitutes.

Buying from a supermarket

You can find out more about the supermarkets’ sustainability commitments using the Ocean Disclosure Project – this database/website collates information voluntarily supplied by the retailers on all their own-brand seafood.

You can find out how much of the range is certified. For farmed fish these must be ASC, BIM (Irish certification) BAP (at least two star) or Global GAP, and for wild fish it must be MSC or a small number of other country-specific certifications. It also recognises fisheries that are part of a Fisheries Improvement Project (FIP). It doesn't recognise organic as a sustainability certification.

Using FIPs as suppliers should be recognised as supermarkets helping to drive improvement though a FIP will not have the same sustainability credentials as a certified fishery. Smaller-scale fisheries often face barriers to achieving certification and by beomcing a FIP, they can overcome these barriers and work towards becoming MSC-certified. 

Buying from a fishmonger or online marketplace

Generally, buying from a fishmonger (or supermarket fish counter) means you can ask for more information about where and how the fish was caught.

The same information that's mandatory for packaged fish should be readily available (displayed somewhere in the shop), but your fishmonger may also have extra details and/or may be able to suggest interesting alternatives to your normal choice.

If you aren't sure about the provenance of something, use the Good Fish Guide. Created by the Marine Conservation Society, this app (and website) gives detailed information about global fisheries for every species you are likely to find in the shops or on your plate. It uses a traffic light rating system, where green equals best choice and red means avoid. 

Often the most sustainable choice will also be what's MSC-certified, but there are also good uncertified choices and using the Good Fish Guide will help identify them.

Online marketplaces such as Pesky Fish, Sole of Discretion and Sole Share can be a good way to try different seafood that is sourced directly from small fisherman. Some are designed for one-off purchases, others are subscription-based, but they tend to be focused on locally caught British seafood and offer a diverse range of fish.