Watch out for the mercury in the fish you eat! How to avoid it, which species to eat

All fish contain mercury, but only four should be avoided. Learn which ones they are and how to choose safe fish without complicating things....

Table of Contents

1. Does all the fish we eat contain mercury?
2. What is methylmercury and how does it end up on your plate
3. The four fish best avoided because of their high mercury content
4. Low-mercury fish you can eat with confidence
5. Special recommendations for pregnant women, children and vulnerable groups
6. How to choose safe fish without going crazy in the supermarket

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Does all the fish we eat contain mercury?

Yes. Practically all the fish that reaches your plate contains some methylmercury. Sounds dramatic, I know, but take a deep breath 😅

The key is this:

• All fish contain mercury in small amounts.


• Only a few species accumulate truly concerning levels.


• Most fish remain safe and very healthy.

Think of mercury like household dust. There's always a bit, but that doesn't mean you live in a cave forgotten by civilization. The problem comes when it builds up.

And with fish it's the same: what matters is not just whether it has mercury, but how much, how often you eat it, and who is eating it.

What is methylmercury and how does it end up on your plate

The journey of mercury is an unromantic but rather fascinating story:

• It's released from volcanoes, coal and oil burning, mining, industry and waste incineration.


• It reaches rivers, lakes and oceans, where many microorganisms transform it into methylmercury.


• That methylmercury accumulates in small organisms, then in larger fish that eat them, and so on.


• The bigger and older the fish, the more mercury it accumulates.

That process is called bioaccumulation. In short:
small fish eat a little mercury, big fish eat many small fish and keep all the mercury. And then we come along with the frying pan.

Why is methylmercury so worrying?

• It mainly affects the nervous system.


• It can damage the brain development of fetuses and young children.


• It can cause tremors, memory problems and cognitive difficulties if exposure remains high for a long time.

The most vulnerable groups:

• Pregnant women 🤰 or those trying to become pregnant.


• Nursing mothers.


• Babies and young children 👶.

For the rest of the population, the goal is not to panic, but to learn to choose fish wisely.

Fun fact:
In the famous Minamata tragedy in Japan, a factory discharged mercury into the sea for years. People who ate fish from that area developed severe neurological problems. Since then, the world has taken methylmercury in fish very seriously.

The four fish best avoided because of their high mercury content

Here's what matters for shopping.
According to various food safety agencies, including the European one, only a few species are really problematic, especially for pregnant women, children and nursing mothers.

In practice, there are four types of fish to avoid in these groups:

• Swordfish or emperor (Xiphias gladius) 🗡️
  Large predatory fish, long-lived and eats other fish. Result: it accumulates a lot of methylmercury.



• Bluefin tuna (Thunnus thynnus)
  Not the typical canned tuna, but the large tuna usually consumed fresh or in high-end sushi. The larger the tuna, the more mercury.



• Large sharks
  For example, commercially caught species like:
  
  
  
  • Mako (Isurus oxyrinchus)
  
  
  • Blue shark (Prionace glauca)
  
  
  • School shark (Galeorhinus galeus and related species)
  
  
  
  They are top predators and accumulate a lot of mercury.



• Pike (Esox lucius)
  A freshwater predator common in lakes and rivers in some temperate areas. It also lives long and eats other fish.

For pregnant women, nursing mothers, babies and young children, the most cautious recommendations usually are:

• Avoid these four options completely.


• Choose smaller, short-lived fish.

For healthy adults in general, many authorities allow occasional consumption of these fish, but skipping them will give you more peace of mind.

And now the question buzzing on social media:
Canned tuna — regular or light?

Comparisons that circulate often rely on commercial categories that change by country. Also, mercury differences between actual cans vary a lot.
Conclusion: obsessing over the label “tuna” vs “light tuna” doesn't give you as much protection as you think. What matters more:

• How much you eat per week.


• What other fish you include in your diet.


• Whether you belong to a risk group or not.

Low-mercury fish you can eat with confidence

Here's the good part: most common fish fall into the “safe” zone ✅

Generally, these have low mercury:

• Small oily (blue) fish:
  
  
  
  • Sardine (Sardina pilchardus)
  
  
  • Anchovy (Engraulis encrasicolus)
  
  
  • Herring (Clupea harengus)
  
  
  • Small sardinella (Sardinella spp.)
  
  
  
  They live short lives and feed low on the food chain.



• White fish:
  
  
  
  • Cod (Gadus morhua)
  
  
  • Hake (Merluccius spp.)
  
  
  • Pollack or Alaska pollock (Pollachius virens or Gadus chalcogrammus, depending on area)
  
  
  • European sole (Solea solea)
  
  
  • Gilthead sea bream (Sparus aurata)
  
  
  • Sea bass (Dicentrarchus labrax)
  
  
  • Farmed trout, e.g. rainbow trout (Oncorhynchus mykiss)
  
  



• Other moderate oily fish:
  
  
  
  • Atlantic mackerel (Scomber scombrus)
  
  
  • Horse mackerel / jack mackerel (Trachurus trachurus and related species)
  
  
  • Farmed Atlantic salmon (Salmo salar)
  
  
  • Pacific salmon, e.g. sockeye or silver salmon (Oncorhynchus spp.)
  
  



• Shellfish and cephalopods:
  
  
  
  • Mussel (Mytilus spp.)
  
  
  • Clams (family Veneridae)
  
  
  • Cockles (Cerastoderma edule and relatives)
  
  
  • Shrimp and prawns (families Penaeidae and relatives)
  
  
  • Squid (Loligo spp.)
  
  
  • Octopus (Octopus vulgaris and related species)
  
  
  • Cuttlefish (Sepia officinalis and similar)
  
  
  
  Shellfish usually have low mercury levels, though they bring other nutrients to balance.

In many countries, food safety agencies recommend:

• 3 to 4 servings of fish per week for the general population.


• 2 to 3 servings per week for pregnant women, always choosing the lower-mercury species.

Nutritional fun fact:
Some of these fish, like salmon, sardines or mackerel, provide large amounts of omega-3.

Special recommendations for pregnant women, children and vulnerable groups

If you're pregnant, breastfeeding or have young children at the table, apply an extra filter.

For pregnant women and those planning pregnancy:

• Avoid:
  
  
  
  • Swordfish or emperor (Xiphias gladius).
  
  
  • Large bluefin tuna (Thunnus thynnus).
  
  
  • Large sharks like mako, blue shark or school shark.
  
  
  • Pike (Esox lucius).
  
  


• Limit canned tuna to a moderate amount per week, according to your country's recommendations.


• Prioritize:
  
  
  
  • Salmon, sardines, anchovies, herrings.
  
  
  • White fish like hake, cod, sea bream, sole.
  
  
  • Varied shellfish in moderation.
  
  

For babies and young children:

• Introduce fish gradually, following your country's pediatric guidelines.


• Mainly use:
  
  
  
  • Soft white fish, without large bones.
  
  
  • Well-cooked salmon.
  
  
  • Small oily fish in age-appropriate preparations.
  
  


• Avoid the four high-mercury fish completely during early childhood.

For people with neurological or kidney diseases, or with a diet very high in fish, it's wise to discuss it with a healthcare professional. Sometimes it's worth adjusting:

• How often you eat fish.


• Which types of fish you choose.

How to choose safe fish without going crazy in the supermarket

Here are simple rules that actually help when you stand at the counter thinking “now what do I buy?” 😅

Rule 1: the smaller the fish, the less mercury it usually has

• Anchovy, sardine, small mackerel, horse mackerel are good friends.


• The giants of the sea often come with “extra mercury”.

Rule 2: rotate species

Don't always eat the same thing.

• Alternate white fish, oily fish and shellfish.


• This dilutes possible contaminants and provides different nutrients.

Rule 3: don't obsess over microdetails on the label

The fight between “tuna” and “light tuna” creates more noise than solutions.

• Focus on:
  
  
  
  • Choosing low-mercury fish more often.
  
  
  • Respecting the recommended weekly portions.
  
  
  • Adjusting a bit more if you're pregnant or breastfeeding.
  
  

Rule 4: fish is still worth it 🐠

Despite mercury, studies show that:

• People who eat fish regularly, especially varieties rich in omega-3, tend to have a lower risk of cardiovascular disease.


• During pregnancy, adequate fish consumption (avoiding highly contaminated species) is associated with better neurological development in the baby.

Rule 5: trust simple rules

If you want an ultra-practical summary:

• Eat fish about 3 to 4 times a week, varied.


• Prioritize sardines, salmon, hake, cod, white fish and shellfish.


• Avoid swordfish, large sharks, bluefin tuna and pike if there are pregnant women or young children at home.


• Don't be swayed by viral alarms that focus on a single type of can without context.

And one last thought:
The problem of mercury in fish exists, but the solution doesn't require a master's in toxicology. You just need a few clear ideas, some common sense and a bit of critical thinking when you see things on social media.

Your plate can keep being full of tasty, safe and nutritious fish. And you can keep enjoying the flavor without methylmercury stealing your sleep… or your appetite 😉

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