Mercury and fish

Most fish in Australia are low in mercury but some are higher and too much mercury can harm developing nervous systems. It’s best to know the mercury levels of different types of fish and how often to eat each type.

Mercury from fish is generally not a health consideration for most people, it's mainly an issue for women planning pregnancy, pregnant women, breastfeeding women and children up to 6 years.

Ready-to-eat, chilled seafood, such as raw sushi, sashimi and oysters or pre-cooked prawns and smoked salmon can be risk for pregnant women because of listeria. Our guidelines have more information about listeria and what to avoid during pregnancy.

Mercury occurs naturally in fish

Mercury occurs naturally in the environment and accumulates in the aquatic food chain, including fish, as methyl-mercury. All fish contain some methyl-mercury, but most fish in Australian waters have very low mercury levels.

Mercury content is not reduced by processing techniques such as canning, freezing or cooking.

Many fish have low mercury levels

The following fish have low mercury levels and are also high in omega-3 fatty acids:

• Mackerel
• Silver Warehou
• Atlantic Salmon
• Canned salmon and canned tuna in oil
• Herrings
• Sardines

Other seafood with low mercury levels include:

• All prawns, lobsters and bugs
• All squids and octopus
• Snapper
• Salmon and trout
• Trevally
• Whiting
• Herring
• Anchovy
• Bream
• Mullet
• Garfish

These fish can be eaten more frequently, up to 2 to 3 times per week.

Canned tuna & salmon

It's generally safe for all population groups, including pregnant women, to consume 2-3 serves of any type of tuna or salmon a week, canned or fresh.

Canned tuna usually has lower mercury levels than other tuna because tuna used for canning are smaller species that are caught when less than 1 year old.

Supplements

Fish oil products and supplements are not a major source of dietary mercury and there is no recommendation to restrict consuming them because of mercury.

Crustacea & molluscs

Crustacea (including prawns, lobster and crabs) and molluscs (including oysters and calamari) are not a concern because they generally contain lower levels of mercury and are usually consumed less often than finfish.

Breastfeeding mothers can continue to eat fish

Fish are rich in protein and minerals, low in saturated fat, and contain omega-3 fatty acids, which are important for the development of your baby’s central nervous system, even after birth.

Although it’s important to continue to eat fish while you are breastfeeding, you need to be careful about which fish you choose. Some fish may contain mercury levels that can harm a baby’s developing nervous system if too much mercury is passed to them through breastmilk.

To safely include fish as an important part of a balanced diet while you are breastfeeding, follow the same guidelines provided to pregnant women.

Fish is good for young children

The healthy nutrients found in fish are excellent for growing children. Simply follow the guidelines for children up to 6 years.

Exceeding the recommended guidelines

Like all foods, fish should be eaten as part of a varied and balanced diet. Over-consumption of any single food group, particularly to the exclusion of other foods, is not recommended because it can lead to dietary imbalances and may increase your intake of potentially harmful substances, such as mercury.

If you have been eating more than 2-3 serves of fish in the past, you can follow the recommended number of weekly portions and your mercury levels will return to normal fairly soon.

Mercury levels will generally halve within several months, providing you follow the dietary advice and limit the amount of Shark (Flake) and Billfish (Swordfish, Marlin) you consume.

If you are concerned about your mercury levels, your doctor can order a blood and/or urine test.

If you choose to eat more than 2-3 serves of fish per week it is important to eat a variety of fish, and avoid those that could have elevated mercury levels, such as Shark (Flake) or Billfish (Swordfish, Marlin).