The facts on fish

CHOICE investigates the benefits and risks of eating fish.
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  • Updated:19 Oct 2008

01 .Introduction

Fishmonger's display

In brief

  • Evidence shows that eating two or three meals of oily fish a week lowers your risk of heart disease.
  • Fish at the top of the food chain, such as swordfish, marlin and shark, could contain mercury at levels that harm infants and small children. These species are also least likely to be harvested sustainably.
  • There are plenty of fish species, both fresh and processed, that are good for you and are harvested sustainably.

We know fish is good for us. It’s low in saturated fat, high in protein and a good source of iodine. Oily fish is rich in omega-3 fatty acids and is a good source of vitamins A and D.

But there are concerns that some fish is contaminated with mercury or other harmful chemicals – and that predatory commercial fishing methods are stripping the oceans of fish, killing seabirds, dolphins and turtles, and destroying coral reefs. CHOICE investigates the benefits and risks of eating fish.

CHOICE verdict

The good news is that we found plenty in fish shops and supermarkets that are both good for you and are harvested with minimal damage to fish stocks or the environment. See our table for the best options.

Please note: this information was current as of October 2008 but is still a useful guide today.


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02.Benefits and risks


The upside of eating fish

These are some of the important health benefits you get from the omega-3 fatty acids EPA and DHA found in fish.

  • Heart health There’s now strong evidence that eating fish can reduce your risk of heart disease. Oily fish in particular is a good source of omega-3 fatty acids and eating it regularly can reduce your chances of a fatal heart attack by 25% or more. The National Heart Foundation now recommends we eat two or three serves of oily fish a week. See the table for the fish with the highest levels of omega-3s.

  • Smarter brains There’s evidence that omega-3s are good for the brain development of infants, even before they’re born. Omega-3s from fish in the mother’s diet cross the placenta, and infants breastfed by mothers who regularly eat oily fish or take fish-oil supplements appear to develop better visual function, which is an indicator of improved brain development. There’s also a growing body of evidence that suggests EPA and DHA may decrease the risk of cognitive impairment and dementia as we get older.

  • Wider benefits Other potential health benefits from eating fish have been suggested but the evidence isn’t as strong. These include lowering the risk of rheumatoid arthritis and, less convincingly, depression and asthma.

The downside of eating fish

Unfortunately fish, especially oily fish, can contain low levels of highly toxic pollutants, and farmed fish can be contaminated by antibiotics and other chemicals used to control diseases. The toxins of greatest concern are mercury and PCBs.

  • Mercury This highly toxic metal can affect brain development in children, even at very low levels. It’s found in small quantities in seawater but it accumulates as methylmercury – the most toxic form of mercury – in the flesh of long-lived fish at the top of the food chain, such as swordfish, marlin, shark (flake) and some species of tuna. The New York City Health Department recently analysed blood samples for mercury and other heavy metals and found significantly higher levels in people who ate more fish.

    Health authorities advise pregnant women, women intending to become pregnant and children under 16 to limit shark, marlin or swordfish intake to no more than one serve per fortnight – and the rest of us should have no more than one portion a week. These species are also best avoided because they’re not likely to be harvested sustainably. As a rule, small fish are good for small children – and pregnant women.

  • PCBs and dioxins These chemicals come from industrial pollution and are a known cause of cancer and may be associated with other health risks as well. They’re in many foods, not just fish. In the US, beef, chicken and pork are the biggest food sources of PCBs and dioxins (34%), while fish and shellfish account for only 9%. In Australia, dioxin levels in fish appear to be low, but questions have been raised about dioxin and PCB levels in imported fish.

  • Chemicals used in aquaculture Fish farmers use antibiotics and other chemicals to prevent disease and parasite infestations. Food Standards Australia New Zealand (FSANZ) has tested for chemical residues in both domestic and imported farmed fish. The tests found the fungicide malachite green in 16% of domestically farmed fish and 17% of imported farmed fish. Testing by the Australian Quarantine and Inspection Service (AQIS) found the antibiotic nitrofuran in some imported prawns. Legally these substances can’t be present in food at any level of concentration, yet FSANZ claims that their findings raise no real public health and safety concerns.

    Food imported into Australia is inspected by AQIS, but it tests only 5% of consignments on average. Fish contaminated with prohibited chemicals are rejected, however, 95% of consignments are not routinely tested, nor are most domestically produced fish.

What CHOICE wants

 CHOICE wants to see Australian consumers better protected by more extensive and more rigorous testing as in the US, where a government surveillance program repeatedly found malachite green and other banned chemicals (fluoroquinolones, nitrofurans and gentian violet) in farmed seafood from China. The US Food and Drug Administration now requires all shipments of some species of farmed seafood from China to be tested. They’re only released for sale when shown to be free of prohibited substances.

03.Fishing sustainably


Worldwide, the demand for wild fish is now greater than the ocean can supply. Southern bluefin tuna was once cheap and plentiful enough to go into canned tuna; it’s now an expensive rarity. There are two main ways of looking at sustainability: is the fish stock sustainable and does the fishing method cause environmental damage?


Australian fisheries are generally well managed, by international standards. But, of 97 stocks surveyed in the Australian Government Bureau of Rural Sciences’ most recent Fishery Status Report, 19 were classified as overfished and/or subject to overfishing. And more than 60% of our fish is now imported.

Fishing methods

All fishing has an environmental impact, but some methods can be particularly destructive of fish stocks and other wildlife. Non-selective fishing gear may catch and kill immature fish and unwanted species thrown away as “bycatch”. Dolphins, turtles and seabirds — often vulnerable or endangered species — can become entangled in nets and killed. Lost or abandoned fishing gear continues to catch fish (and other marine life) until it falls apart — a process that can take years. Two methods are of particular concern.

  • Trawling In this widely used fishing method nets are towed behind a boat and dragged along the ocean floor. Trawling can damage the seabed, destroying marine life and habitats on which the fish depend for food. Trawling accounts for about 50% of the fish wasted as bycatch.
  • Drifting Long lines are used to catch tuna, marlin, swordfish and sharks. A main line, which can be a staggering 10km-80km long, floats on or near the ocean surface. Along this main line there are numerous branch lines with baited hooks. There’s concern about the impact on dolphins, whales and turtles, as well as endangered seabirds, such as albatross. Unfortunately “dolphin safe” or “dolphin friendly” claims on fish products mean very little. There’s no universal and independent verification of such claims. Undoubtedly, many companies try to do the right thing, but there’s no guarantee.

Fish farming

Fish farm - image courtesy of Tassel GroupAquaculture is a big industry in Australia. Snapper, barramundi, southern bluefin tuna, mulloway, Atlantic salmon and trout are grown in sea cages, while prawns are grown in saltwater ponds built in wetlands along Australia’s tropical coast. This might seem to be the answer to the problem of sustainability, but fish farming raises environmental issues of its own.

  • Farmed fish are more crowded than in the wild and therefore more susceptible to disease. Antibiotics and other chemicals are used to control disease outbreaks, and diseases can spread to native fish stocks.
  • Farmed fish can escape from sea cages. Atlantic salmon are voracious predators and can wreak havoc on native fish stocks — so there’s a moratorium on salmon farming expansion in British Columbia, Canada.
  • Dissolved and solid fish waste from sea cages can pollute coastal waterways. Sea-cage fish are fed a diet that uses wild fish, such as sardines and mackerel, to produce fishmeal.

It takes 2-4kg of wild fish to produce 1kg of farmed Atlantic salmon. It would seem more responsible to eat the sardines and mackerel instead — and they're better sources of omega-3s.

Raising fish such as prawns, salmon and barramundi in fully enclosed tanks or ponds seems to be preferable, as the output of waste materials can be controlled. These operations can cause environmental degradation through clearing of mangrove forests and destruction of wetlands, but with appropriate care and expertise, fish farms can be ecologically designed and sustainably operated.

What CHOICE wants

In the UK, the Food Standards Agency is reviewing its advice on eating fish to take into account issues related to sustainability. CHOICE wants the next revision of the Australian Dietary Guidelines to consider the impact of fishing practices in its advice on eating fish.

Image courtesy of Tassel Group Limited

04.Fresh, frozen or canned?


When you’re buying fish, what do you choose? Which fish give you the most omega-3s and least toxic chemicals while coming from a sustainable fishery? In the table we’ve compared some of the species of fish you’re likely to find at your local shopping centre or fish co-op.

Fresh fish

Fresh fish are best for flavour and texture, except when they’re really frozen fish that have been “thawed for your convenience”.

  • Swordfish is an excellent source of omega-3s but is best avoided because of its relatively high mercury content and doubts that it’s being sustainably harvested.
  • Atlantic salmon is a good choice if aquaculture doesn’t worry you for environmental or other reasons.
  • There are Australian species that are harvested sustainably and contain healthy levels of omega-3s. (See the table for details.)
  • Most shops also have basa, a species of catfish farmed in the Mekong Delta in Vietnam. It’s cheap but has very low levels of omega-3s and will have been frozen.

Frozen fish

Packaged frozen fish is a convenient standby that’s quick and easy to prepare. Again, Atlantic salmon is the best choice for omega-3s, but if it’s frozen it might have been harvested from sea cages which can have negative effects on the environment. Hoki is used most often in frozen fish portions. It has lower levels of omega-3s than Atlantic salmon, but still useful amounts. The New Zealand hoki fishery has been certified by the Marine Stewardship Council, so check the label for that logo (see Labels and logos). Other hoki fisheries haven’t been certified and may not be as carefully managed.

Canned fish

Can of red salmonHerring, sardines and mackerel are outstanding for omega-3s. These small fish from northern waters can be harvested sustainably because they’re fast-growing and low in the food chain.

Canned Pacific salmon is also a good source of omega-3s. Also called red or pink salmon, these fish are different species from Atlantic salmon. They’re harvested from the wild, using nets. The Marine Stewardship Council has certified Alaskan but not the Canadian Pacific salmon fisheries, and some brands of canned salmon carry that logo.

Fish miles

Most canned fish comes from the other side of the world, raising the issue of food miles. But preserving food in cans uses less energy and creates fewer greenhouse gas emissions than freezing. It takes more energy to make the can than the cardboard packaging, but frozen foods require more energy for processing and distribution.

05.Sustainable fish table


Sustainable fish table

Table notes

Fish name For fresh fish we’ve used the preferred name from the Australian Fish Names Standard; for processed fish we’ve used the name on the label for ease of recognition.

Omega-3s This gives an indication of the amount of EPA and DHA — the omega-3 fatty acids that confer health benefits — per 150g serving of fish. The actual values vary with the season and where the fish was caught, and some fish names such as ‘pacific salmon’ and ‘prawns’ cover several different species. The recommended daily intake is 600mg for men and 400mg for women.

starstarstar          More than 1000mg per 150g serve.
starstar              Between 1000mg and 500mg per 150g serve.
star                  Between 500mg and 200mg per 150g serve.
empty star                  Less than 200mg per 150g

We calculated the values for processed fish from information on the packaging; for fresh fish from data published by the CSIRO.

Aquaculture See Fish farming

Sustainably harvested This is a contentious issue on which opinions differ, and often there’s a lack of hard scientific evidence. We’ve tried to assess the most likely status of each of the fish in the table based on Australian government and United Nations Food and Agriculture Organisation surveys.

green fish                From what appear to be a sustainable fisheries.

orange fish                Fish that are under pressure and may be overfished.

red fish                Overfished and of significant conservation concern.

(A) Can be from a number of different species.

What fish is that?

approved fish names logoLabels on fish can be confusing. There’s now an Australian Fish Names Standard, but it’s only voluntary. Without this information you can’t be sure what species of fish you’re buying, and it’s even less likely you’ll be able to find out how it was caught. When you’re buying whole fish you might at least have an idea of what you’re getting, but fillets can be a complete mystery.

We found plenty of fish in supermarkets and specialist fish shops with names that aren’t in the standard, and were disappointed to find that some of these are from the big name brands of frozen fish, Sealord and I&J.

Retailers are now legally required to display the country of origin. However, this can be so vague as to be almost meaningless, such as prawns labelled as coming from “China, Vietnam or Thailand”. Manufacturers of canned or frozen fish can also hide behind the catch-all “Made in Australia from local and imported ingredients”.


  • Marine Stewardship Council logoMarine Stewardship Council This international organisation has developed standards for sustainable fishing, which are published on its website. It has certified sustainable fisheries in most parts of the world, including two in Australia. Its logo on canned or frozen fish is a good indication that the product came from a sustainable fishery.
  • Approved fish names Retailers displaying this logo are committed to accurately labelling their fish using the Australian Fish Names Standard.

What CHOICE wants

In the UK many unprocessed fish products must now be labelled with the production method, that is, whether it was farmed or caught in the wild, and where. CHOICE would like to see a similar mandatory system here. Meanwhile, if the species of fish or its country of origin is unclear, don’t buy it.