Newquay sea aerial photo Louis Reed

What makes seafood unsustainable?

4 minute read

The most unsustainable seafood is red-rated in our Good Fish Guide. We need to change how we fish, farm and purchase seafood to help protect our seas.

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Jack Clarke, Sustainable Seafood Advocate

Why should we avoid eating some types of seafood?

The future of the fish supper is no longer guaranteed. Many fish stocks are in a state of serious decline, with overfishing a great threat to marine wildlife and habitats. With 90% of world fish stocks fully or over-exploited from fishing, plus pressure from climate change and pollution, we’re moving into dangerous waters when it comes to the fish of the future.

We are leading the way on changing habits. You can help reduce the strain on certain species by demanding that the fish you eat comes from sustainably managed stocks and is caught or farmed in a way that causes minimal damage to the marine environment and other wildlife. Doing the right thing is easier than you think with our Good Fish Guide – it really can make a difference.

Red-rated wild caught seafood

In the last 50 years, fishing has been the leading cause for loss of marine biodiversity and scientists are concerned about the threats facing our seas.

Endangered species

Did you know that some fish are as endangered as the Bengal tiger? Yet they're still finding their way onto our plates. The European eel, for example, is listed as Critically Endangered. Their populations are at an all-time low and we need to take urgent action to save them.

What needs to be done

We must stop fishing and eating endangered species such as eel until they recover. We must protect their habitats, remove barriers to their migration and reduce pollution in our waterways.

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Overfished and depleted stocks

Overfishing happens when a species is removed faster than it can reproduce. The more that fish stocks become depleted, the greater the risk that they won’t recover at all, which can be devastating for fishers and the marine environment.

What needs to be done

Governments need to make sure that fishing regulations are appropriate and based on the best available science, providing incentives that encourage fishers to adopt best practices on their boats. Businesses and consumers should always seek out the most sustainable seafood and businesses can also use their influence to encourage improvements.

Habitat or wildlife damage

Fishing methods like trawling or dredging can cause long-lasting damage to the sea bed and marine habitats. Additionally, certain practices, involving longlines and gill nets for example, can sometimes accidentally catch vulnerable species like turtles, sharks, seabirds and porpoise.

What needs to be done

Those involved in fisheries management should identify important habitats and make sure they are protected from damaging activities. Fishing practices and gear can be modified so that vulnerable species are avoided as much as possible. This can include avoiding fishing at certain times, adding sections where small fish can escape from the net, using specially shaped hooks or utilising visual and sound deterrents. Crew should be trained to handle vulnerable species with care so they can have the best chance at being returned to the sea alive. Large businesses can be really important in encouraging the uptake of these measures.

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Illegal, Unreported and Unregulated (IUU) fishing

Illegal, Unreported and Unregulated (IUU) fishing occurs around the world and undermines attempts to sustainably manage fisheries. Global financial losses from IUU fishing are estimated to be between US $10 billion and US $23.5 billion annually (between 10 and 22% of total fisheries production).

What needs to be done

Monitoring IUU fishing is a tough task, largely because it occurs a long way from land and across enormous areas of water. Governments need to make sure that they have enough resources to properly monitor fisheries and are utilising the latest technology to do so. Businesses need to ensure seafood is fully traceable and must check that the seafood they buy is from a vessel that was fishing legally.

Red-rated farmed seafood

Unsustainable juvenile fishing

Most farmed fish are grown from eggs that are raised in a hatchery and come from farmed broodstock (parents). For some fish, in particular Bluefin tuna and European eel this is not the case, these species rely on the wild capture of juveniles, which are fished before they can reproduce.

What needs to be done

Research is ongoing, but until both of these species can be raised in a hatchery they remain on our Fish to Avoid list.


Unsustainable fish food

Most farmed fish and prawns are given a pelleted feed, nearly all of which contains fishmeal and fish oil. The fish used to make this feed are not always sustainably managed, leading to their stocks becoming more and more depleted. This has a negative impact on the surrounding ecosystem and other species that rely on them as food in the wild.

What needs to be done

It is important that the fish used to make feed are sustainably managed- this is the only way we can ensure their future. We are seeing some progress, with a number of improvement projects around the world working to achieve this. We want to see incentives from governments to encourage and develop these kinds of projects. Businesses should adopt policies that ensure all feed ingredients are traceable and certified as responsibly managed and produced.

Chemical use

When used in a responsible way, overseen by a vet and within regulations, antibiotics are acceptable and necessary. But they can also be used irresponsibly for things like growth promotion. This is a concern for both the environmental impacts this has on the surrounding ecosystem and for the development of antibiotic resistance.

What needs to be done

There has been a reduction in the use of antibiotics in many fish farms since the development of effective vaccines to treat diseases. Governments need to ban improper uses of antibiotics and introduce regulations that restrict their availability. Businesses should preferentially source certified farmed seafood where chemical use is monitored and restricted.

Untraceable, uncertified seafood

We need to be able to tell if our seafood has been farmed in a responsible way. The packaging our seafood comes in should contain all of the information we need to make an informed choice.

What needs to be done

Buying certified seafood (like the green tick logo of the Aquaculture Stewardship Council) ensures that what we are buying can be traced back to a farm that uses responsible practices. Some farms need help to achieve such certification, and this is happening via improvers projects around the world. Businesses should preferentially source certified farmed seafood and provide information on pack to enable consumers to make the best choice.

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