Food & fluids

Fish and mercury contamination

Red SchnapperFish and shellfish are highly nutritious foods that can contribute much to a healthy diet.

Rich in protein, iodine and some B group vitamins plus vitamins D and E.  Fish is low in saturated fat but contains essential Omega 3 fatty acids (EPA and DHA) that are believed to be important for cognitive development and function.

While fish can also contain some mercury it is still possible to enjoy the health benefits of eating fish and keep the exposure to mercury within safe limits.

Women who are pregnant or considering pregnancy should take particular care to keep within the safe limits as described below.

Concerns regarding Mercury

Mercury occurs naturally in the environment and is found in soil, rocks and water. It is also an environmental contaminant from industry and mining activities.

Mercury is found in three main forms: elemental, inorganic and organic. Methyl mercury is the organic form and the one that is most toxic. This is also the type of mercury that accumulates in fish.

Normally people are not exposed to high enough levels to cause neurological damage because our bodies excrete mercury over time and so accumulation is seldom a problem.

However when fish that have a high level of methyl mercury are eaten, the mercury is absorbed easily into the blood stream and is distributed around the body. Unborn babies and infants are more sensitive to mercury’s harmful effects and so it is important to limit their exposure, particularly to those fish with the highest mercury levels.

Mercury levels in fish

Mercury levels differ regionally and so recommendations vary around the world.

The fish habitat

Mercury levels in fish also depend on the type of fish and their feeding habits. Most fish accumulate only small amounts of mercury throughout their life by eating plants and other organisms in the water that contain mercury. However predatory fish at the top of the food chain, such as shark and swordfish, live longer and so have the time to eat more fish and therefore accumulate higher mercury levels.

Regional variation

Mercury is also found to be higher in volcanic areas. So freshwater fish such as trout, that live in lakes supplied by geothermal water, should be limited to no more than one serving per week or fortnight.

MPI Recommendations in New Zealand

The MPI have identified the many commonly eaten fish in NZ where there is little concern regarding mercury and they can be eaten freely.(1)

  • Mixed fish (e.g. battered fish or fish fingers) are also low in mercury and can be eaten without restriction (1)
  • The Australian New Zealand Food Standards Code has safe upper and lower mercury limits for fish. For low mercury fish the limit is 0.5mg/kg and the higher levels the limit is 1.0mg/kg.(2)
  • A limit for crustacean and mollusks has also been established at 0.5mg/kg (2)

Table 1

No Restriction Necessary Low Mercury Fish High Mercury Fish
Anchovy Albacore tuna Cardinal fish
Arrow squid Alfonsino Dogfish (excluding rig)
Barracouta Bass Lake Rotomahana trout
Blue cod Bluenose Lake trout from geothermal regions
Brill/Turbot Gemfish School shark (Greyboy, Tope)
Brown trout from Lake Ellesmere Ghost sharks Marlin (striped)
Cockles Hake Southern bluefin tuna
Eel, long or short finned Hapuka (Groper) Swordfish
Elephant fish Javelin Fish
Flounders Kahawai
Gurnard Kingfish
Hoki Lake Taupo trout
John Dory Leatherjacket
Monkfish or stargazer Lemon sole
Mussels (green and blue) Ling
Orange perch Mackerel (blue and jack)
Oysters (Bluff* and Pacific) Orange roughy
Parore Oreo dories
Rainbow trout from non-geothermal regions Red cod
Salmon (farmed) Ribaldo
Scallops* Rig (Lemonfish, Spotted dogfish)
Skipjack tuna* Rock lobster
Sole (except Lemon sole) Sea perch
Southern blue whiting Silverside
Surf clams (eg, tuatua) Skate
Tarakihi Smooth oreo
Toothfish (Antarctic) Snapper
Warehou (common, silver and white) Sprats
Whitebait (Inanga Trevally

*Note Pregnant women should limit their intake of Bluff oysters and Queen Scallops due to higher levels of cadmium. (1)

* No data is available for Yellow-fin tuna (1)

Recommendations intakes in Australia and New Zealand

Adults and older children

  • Can consume 150g servings of a variety of fish 2-3 times a week.
  • If fish containing higher levels of mercury (e.g. shark, swordfish or marlin) are eaten then this should be limited to one serving per week but no other fish should be eaten during that week. (2)

Pregnant and breast feeding women

  • Can consume 150g servings of a variety of fish 2-3 times a week.
  • Consumption of low mercury  fish ( e.g. Orange Roughy/ Sea Perch) should be limited to 150g/week and to have no other fish that week.
  •  If consuming high mercury fish (e.g Shark/Flake or Billfish/Swordfish/ Broadbill or Marlin) limit consumption to 150g/fortnight but have no other fish for that fortnight. (2)
  • Pregnant women should limit their intake of Bluff oysters and Queen Scallops due to higher levels of cadmium. The MPI also remind women that shellfish should never be eaten raw in pregnancy. (1)
  • Breast Feeding women can resume their normal diet once their baby is born as breast milk is not considered a significant source of mercury. (1)
  • Note this information has been  updated -please check MPI recommendations below

Children up to the age of six years

  • They are encouraged to consume 75g servings of a variety of fish 2-3 times a week.
  •  Consumption of low mercury  fish (e.g. Orange Roughy / Sea Perch) should be limited to 150g/week and to have no other fish that week.
  •  If consuming high mercury fish (e.g Shark/Flake or Billfish/Swordfish/ Broadbill or Marlin) limit consumption to 150g/fortnight but have no other fish for that fortnight. (2)

Food processing and mercury

As the mercury is bound to the protein in the muscles of fish it is not affected by food processing methods such as cooking, canning or freezing.

Canned or cooked fish

  • These are not a higher risk than raw fish.
  • Tuna used in canning and small fish such as sardines, herrings and pilchards are short-lived species which accumulate low levels of mercury.

Fish oils and supplements

  • These are not a major source of mercury in the diet.

Dried fish

  • Certain ethnic populations may be at higher risk for mercury poisoning if they are consuming imported fish from Asia, especially dried fish.(2)

Overseas travellers

As mercury levels vary regionally it is important that, if consuming fish in countries outside NZ and Australia, you consult the local health authorities if you have concerns regarding specific mercury levels in fish. Particularly if you are pregnant or caring for young children.

If you would like to discuss your family’s diet then contact us today

Note Updated information for pregnant women

2018 List of safe food in pregnancy


For more information on fish and food safety read Lea’s article on:

Fish for good health

Fish for good child nutrition



  1. Mercury in fish report. Ministry of Primary Industries (MPI)
  2. Mercury in fish Food Standards Code 2011
  3. Food safety. Agriculture and Fisheries


About the author View all

Lea Stening

Lea is one of New Zealand’s leading paediatric dietitians and also specialises in Sports Nutrition. She has specialised in Paediatric Nutrition for 31 years and in 1985 was the first paediatric dietitian to enter private practice in New Zealand. Lea helps families through her private consultations, public lectures, newspaper and magazine articles as well as television and radio interviews. Read more »

View all posts by Lea Stening »


Leave a Reply

Also in Food & Fluids View all »

  • Dietary Guidelines are constantly changing:...

    Although science is constantly evolving, generating new recommendations to improve our health, for many people their eating habits are based on things other than their longevity so are guidelines still relevant today? Read more »

  • 5 good reasons for eating eggs

    Are eggs really cheap and nutritious when compared with other protein rich foods? What about cholesterol? and are they safe to eat raw or if you're pregnant? Find out .. Read more »

  • Coffee concoctions

    Whether we sit in or take out it seems our love affair with coffee just keeps growing. Let's take a quick look at the effect our choice of coffee may have on our nutrient intake. Read more »

  • Potatoes – they’re maybe healthier...

    Potatoes are often labelled too starchy, too fattening too boring, but is this fair? As we grapple with Covid-19 maybe it's time to take a fresh look at how eating potatoes nationally could help our health and economic growth Read more »

  • Snacking on the plant-based diet

    Business is booming in the snack food trade. However not all commercially available foods are good for our health. Find out how planning snacks can help to power your day Read more »

  • Can caffeine improve your performance?

    New Zealand ranks 13th in the world for coffee consumption ahead of Australia and USA. What are the effects of caffeine on our health and can it improve our performance? Read more »

  • Soup to soothe

    There is something very comforting about a bowl of soup especially on a cold winters day or if you are feeling unwell. Here we compare soups available today and offer guidelines on choosing the healthiest. Read more »

  • The active life of yoghurt

    Yoghurt is a healthy, economic and beneficial way to supply the body with macronutrients particularly protein and calcium, very convenient as a meal or snack its health benefits could help you. Find out more.. Read more »

  • Alcohol and sport- Is it a good match for you?

    When used responsibly alcohol can help to relieve tensions in athletes and to build feelings of inclusiveness in a team. However in excess it can slowly unravel training, health and sporting careers. Read more »

  • Don’t like fish?

    Fish is high in protein, iron, B group vitamins and essential fatty acids. But not everyone likes it. What can parents do to help their child try it again? Read more »

  • Are nuts all they are cracked up to be?

    Are nuts healthy and how much do we need to eat in order to enjoy their health benefits? Read more »

  • Wise up to Discretionary Foods for better health

    If you are struggling to lose weight or lower your cholesterol then taking a closer look at your intake of discretionary foods can improve your results. Read more »

  • Could you make healthier decisions when shopping?

    Every food item we drop into our supermarket trolley isn’t just affecting us but also the health of those we provide food for. How well do you shop? Read more »

  • How to put ‘real’ flavour into...

    It can be so easy to snip the top off a packet of flavouring when cooking. But if we really want to reduce the salt, fat and sugar in our diet natural flavours are best. Find out how. Read more »

  • Get children cooking this Christmas

    Increasing the confidence of children to cook from scratch is now seen as part of the strategy to reduce chronic diet related disease and obesity. We offer 12 top foods to know how to cook before leaving home. Read more »

  • Garnishes galore and all those “little...

    Is garnishing getting out of hand? Find out how much energy those "add ons" really do add. Read more »

  • 8 tips to help you break the sugar habit

    What habits would you like to break? With all eyes on sugar reduction learn the steps to make this happen to achieve better health now. Read more »

  • Time your eating for better performance?

    If playing sport or exercising, understanding the GI can help you to select foods that will provide optimal energy at key stages of activity for better performance. Read more »

  • What’s the fuss about fructose?

    Sugar has been the focus of attention lately amidst concerns for our dental health and obesity. But what about fructose, the sugar that intrinsically exists in fruits and vegetables? Could this be injurious to our health too? Read more »

  • Get into fruit and vegetables for optimal health

    Do you get your 5+ A Day servings of fruit and vegetables? Learn how gardening and creative activities can improve your consumption of these foods and maximise their nutritional benefits for better health. Read more »

  • 15 Tips for healthier barbeques this Christmas

    Are you planning a Barbeque this Christmas? It's not hard to lower everyone's saturated fat, salt and sugar intake while still serving beautiful, tasty food. Read more »

  • Tips to help you ‘shake off’ the...

    In a bid to reduce the intake of processed foods many food manufacturers are modifying their products to meet new food guidelines particularly regarding salt. Find out if you are still getting too much? Read more »

  • What’s to drink?

    As concern, regarding the sugar and energy content of carbonated drinks and fruit juice, gathers momentum many people are looking for alternative drinks to have. Read more »

  • Is going “Gluten Free” a healthy...

    As the popularity of gluten- free diets grow we need to question whether in fact it is a healthy option for any of us and if not how can we make it so? Read more »

  • 8 Healthy tips when making ‘real food’...

    If we choose a lifestyle where others grow and process our food can we be sure that it is still safe to eat? Find out more. Read more »

  • Does your diet tick all the boxes?

    Is dieting still fun if it ages you? Find out if your diet ticks all the boxes for your better health and performance. Read more »

  • Organic food markets are gaining traction

    Organic foods are more expensive but as more farms convert to organic food production the costs do come down and the savings to the environment by reducing pollution and conserving water and soil quality may, in the long-term, be money well spent Read more »

  • Juice diets – are they as healthy as...

    For busy people, who might rather drink than chew their fruits and vegetables, the juicing trend sounds like a "gods send". What possible disadvantages could there be to health? Find out the pros and cons of this new diet craze. Read more »

  • Taste is important to fluid consumption

    Taste is an important factor affecting fluid choice and level of consumption and therefore is an important consideration to overall sporting performance Read more »

  • Feeling full is the secret to weight loss

    Gaining an understanding of the many factors contributing to a sense of fullness can provide some very powerful tools for those seeking to lose or control body weight and find more energy for life! Read more »

  • Milk matters

    How safe is cow’s milk in the raw and homogenised state? When can cow’s milk be given to infants and how can we protect children against developing allergies to cow’s milk? These are just some of the questions that have come up in the media lately and are in need of some clarification Read more »

  • Muesli and sports bars can aid performance

    Muesli and sports bars are designed to provide a convenient source of energy to be thrown into a lunchbox, gym bag or pocket and eaten “on the run”. However if eaten daily as a “lolly” or relied on as a meal replacement they can lead to unnecessary weight gain. If used wisely during training and competition they can provide athletes with a measured source of carbohydrate vital to performance. Read more »

  • Healthy meals for one

    Coming home to a nutritious cooked family meal was once the norm for many of us. Recent social change however is now seeing more people living in single dwellings many of whom are turning to meals “on the run” that are quick and easy to prepare Read more »

  • Can coconut improve our health?

    Coconut oil was once associated with tanning. Something young people coated themselves with before lying out in the sun “to bake”. Today coconut products are being heralded by many as the new “wonder food" that can cure many ailments. We take a look at some of these claims. Read more »

  • Food planning is important for hiking safety

    Research does show more injuries occur in the mid-late afternoon in open country than other times of day. This is often when people become dehydrated, their muscle levels of energy (glycogen) can become depleted and blood glucose levels may be falling, all factors which lead to fatigue Read more »

  • Sugar control is essential for better health

    After years of encouraging a low fat diet with some success (a decline in heart disease and some forms of cancer) attention is now focusing on sugar as a possible reason for our weight and diabetic problems. Read more »

  • Boosting fibre intake offers health benefits

    Research shows that a diet high in fibre can reduce the risk of developing diseases such as type 2 diabetes, coronary heart disease, bowel and breast cancer, gallstones, diverticular disease and weight gain. It also seems that some fibres are better than others. Read more »

  • How to increase the ‘Good’ fats...

    If you are thinking of cutting fat out of your diet stop right now. Fat is important for nerve and cellular function but choosing the right “type” of fat is what matters most to our long term health. Read more »

  • Can a high fat diet improve sports performance?

    Fat carries more energy than other macro nutrients (9kcals/37kJ/g compared to 7kcal/29kJ/g for alcohol and 4kcal/17kJ/g for protein and carbohydrate respectively). So with so much energy to offer does eating more improve performance? Read more »

  • How much food do you waste every day?

    In New Zealand around 258,886 tons of food waste is dumped in landfill each year. This equates to around 64kg of food waste per person/year in NZ compared to 82kg /person/ year in the USA. Read more »

  • Healthy ideas for family takeaway meals

    Did you know that in 2012 around 21% of New Zealander’s weekly food expenditure was spent on eating out and takeaways? Read more »

  • Are you a “sneaky snacker”?

    Some people find it hard to control snacking and are continuously thinking about food. They may find themselves constantly picking, stock piling foods in drawers and cupboards at home and work. Read more »

  • Give healthier gifts this Christmas

    If you want to enjoy the company of friends and family when you get older then if is important that you look after their health, as well as your own, as you age. Read more »

  • “Free foods” for hungry children

    Free foods", while bulky, are very low in energy and filling. So their cost in terms of calories is much lower than most other dietary components, hence the term "free". As these foods are also naturally fat free they make ideal snacks for anyone trying to control body weight Read more »

  • Party plans for children

    Birthday parties should be fun and the chance to celebrate a child’s special day with a minimum of work and cost for busy parents. If the party can be timed to fit around a normal meal time then “junk” foods can be kept to a minimum. Read more »

  • Care for “the carers” during family...

    When family members are sick or hospitalised it can be very challenging to find the time to exercise and maintain a healthy diet for yourself. Particularly if you are working, caring for children, or trying to complete a course of study. Read more »

  • What are our children drinking?

    In 2015 New Zealanders consumed a total of 518 million liters of carbonated drinks. Outside of the drinking of milk and water there is real concern about the energy content of some of these beverages because of our rising incidence of diabetes and obesity. Read more »

  • Drink milk for better health

    Fonterra’s announcement that it will sponsor free milk in schools is good news for the future health of young New Zealanders. Milk is promoted on the basis of bone health but there are many other health benefits that should be promoted. Read more »

  • Make healthy decisions this Christmas!

    We all like to think that we call the shots regarding what we eat and drink. But who really has the last say over what we swallow? Read more »

  • Marvellous mushrooms

    Did you know? New Zealanders consume 2.7kg of mushrooms per person each year. Mushrooms rank as the third most popular vegetable in this country in 2010. White button mushrooms are the most commonly eaten type of mushroom in New Zealand. Mushrooms do not need light to grow. They obtain all their goodness and nutrients from … Read more »

  • Brace yourself for the brassicas

    With Winter now upon us its time to eat more Brassica vegetables. What are they? Broccoli – 7th most popular vegetable in New Zealand Cauliflower – 13th most popular Cabbage (all types) – 12th most popular Brussel Sprouts Broccolini – consumption rocketing! Swedes Turnips Why are they so good? Brassicas contain: Antioxidants, from the following … Read more »

  • Navigating Christmas without weight gain

    Measurement is an important evaluation tool at any time of the year, it is only human nature to want some means of measuring progress; however can we rely solely upon any particular measure and expect to obtain a reliable result? For each aspect of life we require some measure to determine our successes or failures, … Read more »

  • Alcohol and type 2 diabetes

    The protective role of alcohol in protecting against heart disease has been reported throughout various media sources in previous years, however only recently has it also been shown in people with Type 2 Diabetes. Epidemiological evidence suggests that a light to moderate alcohol intake may have a protective role against the development of Diabetes in … Read more »

  • Sweeteners

    Public awareness of sugars within our diet has slowly increased in recent years. Whilst fat has borne the majority of blame for its implication in development of excess body weight, sugar has escaped relatively lightly. Read more »

  • Warning signs of excess alcohol

    During times of stress it is tempting to reach for alcohol in the hope that it will relax you and take away the pain or sense of loss you may be feeling. Read more »

  • Food safety

    If you do suffer bouts of vomiting and diarrhoea then here are some helpful tips.. Read more »

  • Easter treats

    If given a tray of Easter Eggs can you stop at one or two or do you eat the whole lot? Read more »

  • Slow food

    Slow Food was founded in Italy in 1989.The reaction of an Italian journalist to the opening of the first McDonald’s in Rome. Find out more. Read more »

  • Summer fruit warning

    High levels of fructose may lead to increased blood levels of triglycerides and lactate. This can be of concern to those who are overweight, diabetic or have elevated blood cholesterol levels. Read more »

  • Fish for good health

    Through out your life, eating fish regularly can greatly improve your health and fitness. Read more »

Would you like to subscribe to our fantastic FREE monthly newsletter?

Each month we'll keep you up-to-date with the latest nutritional articles and healthy recipes from You are free to opt out at any time, but we think you'll enjoy what we've got in-store for you.

Plus as a bonus offer — subscribe today and receive FREE weight loss tips for two weeks! Learn how a number of foods, many one would consider 'healthy', may in fact be slowing your progress.


Yes please, it sounds great! (and it's FREE after all).



No thanks, I'm not interested (or I'm already a subscriber and really enjoying these fantastic newsletters!).