People on beach in Lyme Regis Nick Fewings

A guide to sustainable seafood

12 minute read

From why we work on sustainable seafood to the impacts of climate change, here's everything you need to know.

Fisheries & Aquaculture Team

About sustainable seafood

Why is choosing sustainable seafood important?

Our seas face a wide range of threats, including climate change, pollution, habitat loss and biodiversity loss. The UN has named unsustainable fishing as the greatest driver of marine biodiversity loss in the world. 94% of global fish stocks are fully or overexploited.

Over 2 billion people around the world depend on seafood as their primary source of animal protein, and with an ever-growing population, there is increasing pressure on our ocean to supply us with food. It is critical that we meet our future protein needs whilst ensuring the health, diversity and productivity of our marine environment. Well-managed fisheries and aquaculture can provide us with low-carbon protein for generations to come.

By choosing only sustainable seafood, we can help minimise damage to vulnerable habitats and species. When consumers choose sustainable seafood, it encourages supermarkets and restaurants to demand it from their suppliers. This demand can reward fishers and fish farmers who adopt sustainable practices and encourage governments to improve management.

Over time, we've seen that the market demand for more sustainable seafood is encouraging real improvements in the management and operation of fishing and aquaculture.

Why does an environmental organisation encourage people to eat any fish?

We believe there is a firm place for responsible, well-managed fishing and aquaculture in our vision of healthy seas.

Wild-caught and farmed seafood is an important source of protein for billions of people around the world and it supports the social and economic prosperity of many coastal communities and countries, including in the UK.

97% of UK households eat fish and we want to make sure that they choose the most sustainable options, from the green end of our ratings spectrum. We believe that demand for only sustainable seafood can help encourage improvements in unsustainable fishing and fish farming practices. There is also increasing evidence that some forms of seafood can provide an important source of low-carbon protein, which is crucial for our changing climate.

Why do we have recipes for seafood on our website and our Good Fish Guide?

In the UK, about 80% of seafood sold is from just 5 species groups (cod, haddock, salmon, tuna and prawns) despite the UK catching and producing a wide range of species that can be more sustainable.

By sharing recipes for other species, we hope to encourage people to diversify their seafood choices and try more sustainable local options. This reduces pressure on wild populations, and also supports local fishers and producers.

About the Good Fish Guide

What is the Good Fish Guide, and how are ratings calculated?

The Good Fish Guide uses the best scientific advice available to provides sustainability ratings for wild-caught and farmed seafood. We use a traffic light system to indicate how sustainable seafood is. Red-rated seafood is “Fish to Avoid”, amber is “OK - Needs Improvement”, and green-rated is “Best Choice”.

We look at complex issues surrounding seafood sources in the UK, including fish population sizes, the use of fish feed, effectiveness of management, and the impact of fishing and farming practices on the environment. Then we collate the information to produce our traffic light rating.

Our ratings empower people to make responsible choices, helping to look after our seas and marine wildlife. Businesses that use the Good Fish Guide sell over 20% of the seafood consumed in the UK. Over time, we've seen that the market demand for more sustainable seafood is encouraging real improvements in the management and operation of fishing and aquaculture.

Good Fish Guide

Our Good Fish Guide has all the advice you need to choose sustainable seafood. Start by searching for your favourite seafood below.

How accurate and up-to-date is the Good Fish Guide?

Good Fish Guide ratings are updated regularly and we carry out two public ratings consultations a year. We ask scientists, fishers, and businesses to send feedback so that we can use all of the information available.

Our work is transparent and credible: we strongly believe it’s essential to rely on what the science tells us. Our ratings are based on peer-reviewed and publicly available literature and data from independent and unbiased scientific institutions, such as the International Council for Exploration of the Sea (ICES).

What is red-rated seafood?

We rate the least sustainable seafood as a ‘Fish to Avoid’ or red-rated option. Seafood can be red-rated because of overfishing, habitat damage or because the species is listed as Endangered or Critically Endangered, like the European eel.

These options have significant environmental impacts, so we recommend avoiding them entirely.

Different fish stocks and fishing or farming methods mean that a single species can have a range of ratings, depending on how and where it's caught or farmed. Cod, for example, could be red-rated in one fishery and green-rated in another, so it’s always important to check the label to know what species you’re buying, how it was caught and farmed, and where.

You can also check for eco-labels for sustainability information. Keep an eye on the Good Fish Guide website.

MCS vs MSC

The Marine Conservation Society (MCS) and the Marine Stewardship Council (MSC) can be easily confused! We both focus on sustainable seafood, but in different ways.

We're the Marine Conservation Society: a UK-based and -focused charity that, alongside multiple other areas of work, runs the Good Fish Guide. We also work to improve the worst performing fisheries and fish farms through engaging with government and other key stakeholders to develop better policies and legislation. We don't charge for our work on the Good Fish Guide - it's a free resource for all to use.

The Marine Stewardship Council, most recognisable by the ‘blue fish tick’ on seafood packaging, is an international non-profit organisation. MSC certification is a global sustainability standard for wild-caught seafood, and includes traceability requirements for trading certified products. In order to get the certified ‘blue fish tick’ fishers or companies need to pay for an assessment to be undertaken by a 3rd party.

We recommend choosing MSC-certified seafood, as these products are often rated well on our Good Fish Guide and are fully traceable. Around 17% of the world's fisheries by weight are now certified by the Marine Stewardship Council. Many fisheries fall outside this process, but not necessarily because they are unsustainable. The Good Fish Guide helps businesses and consumers to better understand the sustainability of fisheries and aquaculture systems that aren't certified.

What to know about buying seafood

Farmed or wild – which is best?

Simply put, neither method of producing fish is better than the other. Both have species on the Best Choice and Fish to Avoid lists, with many options in between.

Wild capture fisheries can be harmful to the seabed, and may result in unwanted bycatch, catching species like dolphins and sharks accidentally.

Aquaculture can impact the environment through pollution from chemicals, escaped fish and disease impacts.

This is all considered in the Good Fish Guide: our ratings take into account the relative sustainability and environmental impacts of all methods.

How important is it to choose seasonal fish?

Wild fish need to be allowed to grow to maturity and breed. They do this at different times of the year depending on the species and region.

However, it is difficult to apply seasonality to a lot of seafood because it is often caught and then immediately frozen. It might be sold months after being caught, and the date of the original catch can be difficult to find out.

Climate change is having some effect on breeding seasons, as temperatures and seasons change, so we could some changes in how we approach seafood seasonality in the near future. However, if you are buying local, freshly-caught seafood, it is important to check that it wasn't taken during its spawning season.

Seasonality doesn't apply to farmed seafood because they don’t breed and reproduce in the same way as wild caught fish.

What should I look for on seafood labels?

The easiest things to look for are credible eco-labels such as the Marine Stewardship Council (MSC) for wild caught seafood, or Aquaculture Stewardship Council (ASC), Soil Association or Organic for farmed seafood.

Some examples of the labels to look out for are below.

ASC Logo Landscape Soil Association Logo English EU Organic Logo GlobalG.A.P. Logo Landscape GAA BAP Logo

Seafood caught or produced to these standards is likely to be rated quite well on our Good Fish Guide and is also subject to robust traceability requirements.

It's also really important to find out what species is it, where was it caught or farmed, and how. These factors can make a big difference to sustainability and allow you to use tools like the Good Fish Guide to make an informed choice.

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Unprocessed products (e.g., not tinned, breaded, or mixed with other ingredients) are legally required to have this information on pack (with the exception of the farming method).

Many brands choose to include this and additional information anyway to improve transparency and traceability.

If it says ‘sustainably sourced’ on a product, is it definitely ok to eat?

You might see sustainability claims like 'Responsibly Sourced' or Sustainably Sourced' on seafood packets.

These claims often relate to a voluntary sourcing code of conduct by these businesses and can be an indicator that the seafood is a good choice.

As these codes are voluntary, some businesses implement them better than others. So, in practice, there can be a wide interpretation of what is actually 'Responsibly Sourced'. It's not a fool-proof way of making the best choice.

If the labelling information is insufficient for you to make an informed choice (i.e., it doesn’t say what species is it, where was it caught or farmed, and how), ask staff or the fishmonger/waiter for more information.

If you can’t get the information you need to make an informed choice, give it a miss!

How do I know if seafood in a restaurant is sustainable?

If the restaurant has a website, that’s always a good place to start. They might have a page on where their food is sourced.

If you spot logos from the Sustainable Restaurant Association (SRA) or the Soil Association it’s usually a sign the restaurant cares about sustainability.

For specific menu options, keep an eye out for credible certification labels like MSC, ASC and organic.

You could also ask the restaurant themselves, and see if they know how and where the fish has been caught or farmed so that you can search for the rating on the Good Fish Guide.

Be wary of phrases like ‘local’, ‘fresh’, and ‘wild’, which are quite often used to imply sustainability but don’t necessarily relate to it at all.

About fishing and fisheries

What are fisheries?

A fishery is a clearly defined area where specific species of fish are caught using a particular method of fishing.

The English Channel trawled cuttlefish fishery, or the Indian Ocean pole and line skipjack fishery, are two examples.

The scale of fisheries varies dramatically. The industrial Peruvian anchovy fishery catches 8 million tonnes per year, whilst the commercial Shetland brown crab fishery catches less than 550 tonnes per year.

A fishery can be commercial, industrial or recreational. Commercial fisheries provide food for human consumption, with the fish being caught and sold to supermarkets, restaurants, or the general public.

Industrial fisheries mainly catch food for non-human consumption - mostly to feed fish on fish farms, to make supplements such as cod liver oil, supply agriculture, or for the pet food trade.

Recreational fisheries tend to be mainly for individuals to fish. In the EU, recreational fishers are not allowed to sell what they catch.

What is Maximum Sustainable Yield (MSY)?

MSY is the maximum amount of fish that can be caught year after year whilst keeping the fish population at a healthy size. It's an estimated figure, often used by fisheries scientists and managers as a target level to keep fishing sustainable. If fishing exceeds MSY, then overfishing is taking place. If the fish population falls below a healthy size, then it is in an overfished state. Globally, 34% of fish populations are overfished.

About aquaculture

What is aquaculture?

Aquaculture is a general term for the farming of aquatic species, from fish and shellfish to seaweed. It incorporates everything from a few mussel ropes on a Scottish croft to huge salmon farming companies on the New York stock exchange.

It is the fastest growing food production sector, growing at a rate of 5.5% per year. In 2016, aquaculture produced over 114.5 million tonnes, including plants. Over 82 million tonnes of this were food fish. In 2018, over 600 species were farmed globally, via an array of scales and methods.

Atlantic salmon is the most commonly farmed fish in the UK. In 2019, 203,881 tonnes of salmon were produced from farms off the coast of Scotland.

Should salmon farming be red-rated?

Salmon farming does have its problems, and the main concerns include sea lice, disease management and impacts on wild salmon populations.

However, it has also made some great improvements in recent years, such as responsible sourcing of feed ingredients. Compared to other fish farms globally, Scotland has a comprehensive regulatory regime.

A 2019 review of the Scottish salmon farming industry highlighted the remaining concerns regarding the environmental performance of salmon farming and identified mechanisms to improve them, including a regulation review. We’re working to ensure that these concerns are fully addressed and improvements are delivered.

For more information see here: https://www.mcsuk.org/news/is-scottish-farmed-salmon-sustainable and our Salmon farming position statement here: https://www.mcsuk.org/media/salmon-farming-position-statement-2020-final.pdf

Should we be feeding fish to fish?

Farmed fish such as salmon, prawn, bass and bream all require feed for their health and welfare.

Aquaculture feed comes in the form of pellets, which include ingredients like fishmeal, fish oil, wheat gluten, soya meal and a variety of other plant-based proteins and oils. The proportions of each of the ingredients in the pellets varies depending on the species they are being fed to.

If there is fishmeal and fish oil in the pellets, they have been derived from either whole fish or trimmings. Most of the fish that is used to make fish feed comprises species that we don’t eat much of – blue whiting, Peruvian anchovy, menhaden, etc.

Alternatively, the fish might come from trimmings from factories that are processing fish for human consumption.

We feel that it is vital that the fish used to make feed are initially made available for human consumption. Only when that market has been filled should alternative uses for fish be sought. It is also important that the fish content of feed comes from trimmings and processing waste as much as possible.

It is essential that fish caught to make feed are sustainably managed.

We also believe that all farmed fish should be net producers of fish protein. This way, we encourage the industry to use innovative ingredients to replace as much fish as possible, such as algae oil, insect meal and protein from fermentation.

As 94% of global fish stocks are fully or overexploited, we are increasingly reliant on aquaculture to meet global demands for seafood. It is critical that we meet our future protein needs whilst ensuring the health, diversity and productivity of our marine environment.

About climate change and ocean health

Do Good Fish Guide ratings factor in the carbon footprint of seafood?

Whilst we recommend going local for your seafood to minimize food miles, improve traceability and support local businesses (read more here), our Good Fish Guide doesn’t currently factor in greenhouse gas emissions.

Our focus to date has been on the direct environmental impacts of fishing and aquaculture operations.

If you’d like to check on the carbon footprint of your seafood there are some great tools such as the Seafood Carbon Emissions Tool from Seafood Watch.

How does climate change impact fish and other marine life?

Climate change has many impacts on the marine environment.

Rising sea temperatures are increasing numbers of harmful algal blooms, sea lice and diseases. In aquaculture, there is a risk that these can kill farmed fish unless treated with chemicals, which can be unfriendly to the surrounding environment.

In wild fisheries, increasing temperatures are affecting the geographical range and population sizes of some fish. Species including anchovy, seabass, hake and lemon sole have all been listed as likely to increase in UK waters, but colder-water species like cod, haddock and plaice have already (or are expected to) move deeper and further north, to stay in cooler waters.

Warmer water can also produce oceanic dead-zones or ‘blobs’ - unusually warm and oxygen depleted bodies of water. This can wreak havoc on any species in their path.

Another serious result of climate change is ocean acidification, which affects the ability of shellfish species (like oysters, mussels and prawns) to generate and maintain shell thickness.

Climate change also leads to sea level rise and increased frequency and severity of storm events and coastal inundation, which could damage wild and farmed fishing operations, as well as ports and processing infrastructure.

What are Marine Protected Areas (MPAs)?

MPAs are areas of sea that are set up to look after particular seascapes, habitats and species, just like nature reserves and national parks on land.

The planned network of MPAs around the UK is designed to protect the places that are home to rare or threatened plants and animals, as well as an array of important habitats.

They can also support sustainable fishers and sea anglers, who can benefit from increased numbers and diversity of fish inside and outside of MPAs.

Find out more about MPAs here.

About ethics and welfare

Does MCS work on animal welfare?

Currently, welfare standards aren’t in place for wild capture fisheries, but they do exist for many farmed species such as salmon and other finfish.

These standards are set by law and in voluntary codes of practice and certifications such as RSPCA Freedom Food.

In our Good Fish Guide ratings for farmed fish, we consider requirements for animal welfare, including humane slaughter.

We recognise that good welfare practices are important and we currently defer to other organisations with the skills and experience in this field, such as Farm Animal Welfare Committee and the RSPCA.

Are there social and human welfare issues associated with seafood production?

Seafood is a hugely diverse sector. Fishing, aquaculture and seafood processing take place all over the world, involving a wide variety of cultures and regulations.

Despite this diversity, workers are entitled to be treated fairly, without having their basic human rights ignored or infringed.

As seafood is produced and traded globally, UK consumers are able to buy fish from countries that don't have the same standards of social welfare as we have. In some cases, those workers’ rights are absent or ignored.

Labour violations on fishing vessels are an ongoing global issue, and are often associated with Illegal, Unreported and Unregulated fishing (IUU). International treaties like the Port States Measures Agreement have been implemented to tackle IUU. They make it increasingly difficult for seafood caught by vessels operating illegally to enter the supply chain.

Organisations such as the International Labor Organisation and the Environmental Justice Foundation also carry out great work in this area.

We defer to and support the work of organisations such as these, including those defining responsible practices for aquaculture, to define and promote high social standards.

About health

What about chemicals and plastics - is it safe to eat seafood?

The NHS say that ‘a healthy, balanced diet should include at least 2 portions of fish a week, including 1 of oily fish. This is because seafood is a good source of many vitamins and minerals’ However, some seafood can contain low levels of pollutants that build up in the body. For this reason, there is specific advice for consuming certain seafood:

  • Girls, pregnant women, those that want to get pregnant one day and breastfeeding women should limit their consumption of oily fish (as well as sea bream, sea bass, turbot, halibut, rock salmon and brown crabmeat) to 2 portions a week. Everyone else should limit consumption of these to 4 portions a week.
  • Pregnant women or those trying for a baby should limit their consumption of tuna to 4 cans or 2 tuna steaks a week.
  • Vary the species of fish you are consuming, because different species have different levels of pollutants.
  • There are limits for everyone on the consumption of shark/swordfish/marlin of 1 portion a week, although children, pregnant women or women wanting to get pregnant shouldn’t consume any of these.
  • Anyone can consume unlimited amounts of white fish other than the species specifically mentioned above (sea bream, sea bass, turbot, halibut and rock salmon).

For further information, please visit the NHS website.