Eat fewer prawns (and scrimp on the shrimp)

Last updated Wednesday 30 April 2008

Seek out more sustainable seafood

The prawn-fishing industry is the most energy-intensive and wasteful fishing industry on Earth. So is it the end of the line for prawns?

By the time a prawn makes it to your sarnie, there's a good chance it's been on a cruise to the Far East to be hand-peeled, deep frozen for a month and shipped back. And the trawler that caught it coughs up more than 20 times as much greenhouse gas in just over a week than a small diesel car does in a whole year.

Farmed prawns put paid to the trawling but destroy valuable CO2-soaking-up mangroves. Small, cold-water prawns may be a less-bad option than tropical 'tigers', but neither variety is a clear choice for the carbon-conscious.

That said, some near-shore seafoods (like clam, crab and lobster) can be harvested without trawlers, requiring relatively little energy. Could it be time to broaden your palate?

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Photo: Eat fewer prawns (and scrimp on the shrimp)

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Pub Fact

  • For every kilo of shrimp caught, 40kg of other marine animals are discarded on average
  • The total area of the world covered by mangroves was 15 million hectares in 2005, reduced from 19 million hectares in 1980
  • The EU is the world's biggest importer of prawns
  • Approximately 5 million metric tons of shrimp are produced annually
  • Shrimp fishing in the North Sea can require about 1.5kg of fuel per kilo of shrimp caught

Prawn fishing is not just energy-intense. It is the most energy-intensive fishing industry on Earth, according to Swedish research. Producing a kilogram of trawled, de-shelled prawns uses about ten times more energy than producing the same weight of clams. In fact, prawn trawling uses almost 20 times more fuel per tonne of catch than the small-fish industry according to research by Dalhousie University in Canada.

All in all, global fisheries use over 1% of global oil consumption - as much as the entire national consumption of the Netherlands.

Trawling accounts for the lion's share (about 70%) of a wild prawn's footprint. In fact, a typical diesel-powered shrimp trawler on a ten-day trip emits about 37 tonnes of CO2. That's about eight times as much CO2 as the average Brit produces in a year.

Bottom trawling for seafood is fuel-intensive because it involves dragging nets that are a kilometre long and as tall as eight double-decker buses along the ocean floor, with up to 15 tonnes of weights attached. This can destroy valuable sea-bed ecosystems and the carbon-storing phytoplankton that sometimes depend on them.

Sadly, prawn farming - the main alternative to wild prawns - is hardly sustainable either. Yet farmed shrimp is one of the fastest growing forms of aquaculture, now accounting for one-third of the shrimps produced globally. Built on tropical coastline, shrimp farms require the clearance of mangroves - coastal swamps that soak up CO2 from the atmosphere and so protect against climate change. In fact, new shrimp farms have been linked to almost half of all global mangrove loss to date. Plus, shrimp are carnivorous, and farming them intensively requires protein feeds (often wild fish) of more than double the weight of the prawn produced.

Fewer mangroves also mean fewer fish because 85% of all commercially-fished species depend on mangroves as nurseries in the tropics, according to the United Nations Environment Programme.

For the average Brit - who eats just two bags of frozen, trawled prawns a year - giving up prawns altogether would save about a third as much CO2 as putting a water saving device in your toilet - or as much CO2 as is released by the production of a CD. Of course, if prawns are a regular feature on your dinner table then the potential carbon savings from cutting down are much larger.

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What's the debate?

"I only buy 'sustainable' prawns. Surely that means they're climate-friendly?"

Nope. While 'sustainable' seafood is certified to be environmentally-friendly, it isn't necessarily doing the climate any favours. This is because the Marine Stewardship Council only takes into account environmental impact and stock-sizes - not CO2 emissions - when deciding a seafood's sustainability. For example, the Oregon Pink Shrimp is certified as sustainable despite the fact that the carbon footprint of its harvesting method has yet to be assessed, according to the Shellfish Association of Great Britain.

"Is eating prawns that are shelled by machine in the UK better for the climate than eating prawns that are shipped to South-East Asia to be hand-shelled?"

While food miles (the distance food has to travel to get to your plate) generate emissions, how the food is produced tends to be far more important. In fact, the Carbon Trust found that prawns shipped to South-East Asia to be hand-shelled are no worse for the climate than prawns shelled in the UK, because of the energy-intensity of shelling machinery in Britain. Read more about it in this Times article.

"If we don't buy tropical prawns, then won't local communities' livelihoods suffer?"

Although the shrimp industry is lucrative for some, the pollution, disturbance, and social conflict created by trawlers can reduce local fish stocks and destroy the livelihoods of subsistence fishermen, threatening food security in some of the world's poorest countries.

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What's stopping me?

"But I love prawns"

If you simply can't go prawn cold-turkey then seek out British trap-caught varieties. They're fairly difficult to find, so the next best thing for the environment is the sustainable, cold-water prawn. Best of all, try to swap prawns for other low-energy seafoods. (Check below for tasty low-carbon alternatives.)

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How do I do it?

  • Choose low-carbon seafoods that have low-energy fishing methods. Look for line-caught, trap-caught and hand-gathered seafoods like pot-caught prawn, creel-caught Dublin Bay prawn, mussel, lobster, crab, clam, Burry Inlet cockles, beach-caught North Yorkshire sea bass and herring
  • If you can't avoid prawns, look for cold-water, sustainably-managed prawns from Norway, Iceland, Denmark, Greenland and Canada. Cold-water prawns are small and white, whereas tropical 'tigers' are large and brown
  • Avoid scallops, which require energy-intense dredging. Also try to avoid other energy-intensive fishing industries, such as tuna and swordfish - which frequently consume in excess of 2000 litres of fuel per tonne of landings
  • Check on the Marine Conservation Society's website for supermarkets that are likely to stock 'sustainable' prawns: Fish Online
  • Read the Environmental Justice Foundation's guide to prawn purchases

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Jo 2009-02-16

I used to work on a trawler, many years ago, for scallops in the Indian ocean. The scallop trawlers worked in much the same areas and with much the same method as the prawn trawlers and they wreaked absolute devastation on the seabed. We were trawling up sea snakes, turtles, seahorses (which die very quickly out of water), sea sponges, really the entire marine ecosystem and I later discovered that the boat I worked on had trawled up a dolphin - but threw it back in dead because they didn't want to report it. The blokes who worked on the boat were bored and would shoot seabirds and break the noses of the shovelnose sharks before throwing them back in, to watch them frantically trying to swim down and being unable to - needless to say, I didn't work on the boat very long!

As for farmed shrimps, the destruction of the mangrove swamps, as described in the article above, was responsible for making the effects of the 2004 Boxing Day tsunami worse, because the coastal areas had less protection. What's more, coastal communities have been prevented from moving back to the areas they used to live in by commercial shrimp farming industries. So this one is very much a human rights issue as well as an environmental one.

Happy crab eating everyone!

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Glossary terms used on this page
CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
Carbon is the fourth most common chemical element in the universe, and carbon compounds - in other words, carbon chemically combined with other elements - are the basis of all known life forms on earth. Pure carbon appears in many apparently diverse forms, from diamond to graphite to charcoal, but it is much more commonly found in substances such as coal, oil, natural gas, wood and peat that we use for fuel. When we burn these substances to provide energy - either directly in our homes as heat, or in power stations to produce electricity - the combustion process produces 'oxides' of carbon, including the gas CO2.
Carbon footprint
A person's carbon footprint (or that of a particular household, business or entire community) refers to the CO2 for which they are responsible - whether directly, via their home energy use, their transport use, or indirectly via the embodied energy in the products and services they buy and use. You can work out your carbon footprint using calculators such as the Government's Act On CO2 Calculator.
Climate change
Climate change is the variation in the average global or regional climate as measured by yardsticks such as average temperature and rainfall. This variation is caused by both natural processes and human activity. Weather is what happens over days or even hours, whereas climate is the average weather measured over a longer period. Increasingly when people refer to climate change, however, they specifically mean the phenomenon of global warming.
Ordinary diesel, like regular petrol, is refined from oil but it is a thicker, heavier liquid with a higher 'energy density' - meaning it offers better fuel economy. On the down side, unless you buy an air filter, diesel exhaust is a significant source of particulates and other sources of air pollution. A type of diesel not derived from petroleum is increasingly widely available, commonly referred to as biodiesel.
Eco-friendly, or environmentally friendly, is a term applied to goods, services, processes or people deemed to do minimal harm to the environment. The term is shorthand for 'ecologically friendly', ecology being the study of the relationships between living organisms and their environment.
An ecosystem is the term applied to the interaction of a community of different living (organic) species - plants, animals and micro-organisms - with non-living (or inorganic) factors, such as atmospheric gases, temperature and light. When the balance of an ecosystem is changed - by the introduction of new elements or dramatic rises in one or more of them - the normal functioning of the ecosystem can be disrupted.
Emissions are the CO2 (and other greenhouse gases) produced by energy use, usually calculated and stated as an annual tally: also referred to as your carbon footprint. Your personal emissions can be direct - such as the gas you personally use to heat your home or the petrol you burn to power your car - or indirect - meaning the energy use that has gone into the products or services you buy. The latter, such as the emissions caused by the manufacture of your new TV, or the packaging your food comes in, are also referred to as embodied emissions.
Energy intensive
An energy-intensive process uses a great deal of energy - and therefore produces high emissions - relative to its useful output. As an example, beef production, has recently been cited as an especially energy-intensive industry, while tumble dryers are energy-intensive appliances. Products that are manufactured in an energy-intensive way are also said to be 'emissions heavy'.
Greenhouse gases
Greenhouse gases raise the earth's temperature through the greenhouse effect. There are six main examples. As well as carbon dioxide, they include: water vapour, methane, nitrous oxide, ozone and CFCs (which include sulphur hexafluoride, HFCs, and PFCs). Of these, carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, HFCs, and PFCs are controlled under the Kyoto Protocol to limit their concentration in the atmosphere. The heat warming capacity of each gas is measured by its 'global warming potential': how much heat it traps depends on its chemical make-up and how long it stays in the atmosphere.
Sustainability - whether applied to energy, technology, industry, agriculture or just consumption of resources in general - refers to the concept of using things at a rate that, while meeting our own needs, does not compromise future generations' ability to meet theirs. In environmental terms, a process or industry is unsustainable when it requires natural resources to be used up faster than they can be replenished. navigation


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