Mercury Levels in Fish – From High to Low


Image used by the BBC to show the varying levels of mercury in fish

Mercury Levels in Fish – From High to Low *KNOW YOUR FISH*

So for those of you who do not know, I am recently pescetarian and this has naturally lead me to think more about the fish I eat. One consideration is the level of Mercury in fish. I need to know this information for myself but I thought it may be helpful to share it with y’all who eat fish; whether on a regular basis or on occasion.

Please note: I am excited to write this, as it is my first requested post. 🙂 

Why should you be concerned with the level of Mercury in Fish?

Most fish/seafood contain some level of Mercury, even if only a trace. This can be harmful to human health as mercury itself is a toxic/harmful pollutant that can damage the nervous, digestive and immune systems; including certain organs, such as the lungs and kidneys. If high levels of Mercury are consumed or inhaled, it can be fatal.

To minimise their risk, pescetarians and other fish eaters will typically look carefully to find fish that is low in Mercury and limit their consumption of fish higher in Mercury. In addition, it is thought that eating more foods containing Selenium, such as eggs and spinach can reduce the effects of Mercury.

The above was taken from my previous post

How does Mercury get into the Fish we eat?


During the burning of fossil fuels and mining of iron, Mercury is released into the air. Mercury eventually contaminates water sources where fish are when it rains. This is then absorbed into the fish bodies. Over time, something called bio-accumulation occurs, which essentially means that fish higher up the food chain accumulate even higher levels of Mercury than the fish they ate, as they eat many of the same fish that contain Mercury. As more Mercury is absorbed by fish, it turns into a toxic form, Methylmercury. This is bad as Methylmercury bonds to proteins in the fish, meaning it cannot be removed during washing or cooking. You may find this guide from the BBC useful.

The age of the fish will also make some difference, as the older the fish, the more opportunity it has to build up Mercury in its body through eating fish during its life. Therefore, some younger fish such as young albacore tuna is often associated with lower levels of Mercury than albacore tuna that is more mature. Whether fish is caught when it is young or old depends on the country it is imported from.

To think that the dominating reason for Mercury in food is due to human activity is depressing to say the least. Opportunities to try fish now higher in Mercury is unfortunately reduced because some people are understandably worried about the Mercury content in the fish that they would then take on by eating it. I’m not going to lie, some of my favourite fish is higher in higher in Mercury, and it is a shame because fish higher in Mercury is typically wild, meaning that people will tend towards eating farmed fish lower in mercury. Thus, due to human activity, some of the tastiest fish is being denied to us. On the other hand.. we (humans) are to blame for this occurrence, from using non-renewable fossil fuels as an energy source to power our homes, our cars and machinery (as well as many others) instead of using renewable energy, such as wild and solar.

You may like to see this YouTube video for a some visuals and more information. 

Fish relatively High in Mercury

Generally fish higher up the food chain has more Mercury, but it also depends on where the fish are caught. Women who are pregnant or nursing, and young children should avoid fish high in Mercury due to the negative effects on cognitive development. The following are all considered to have high levels of Mercury and their intake, if any, should be limited. For selected fish (*) if you choose to eat them it is recommended that you eat less than three 6-ounce servings per month.

  • King Mackerel/Kingfish

    King Mackerel
  • Spanish Mackerel*
  • Gulf Mackerel*
  • Shark
  • Swordfish
  • Fresh/Frozen Tuna (Tuna Sushi, Bluefin, Yellowfin*, White ‘Albacore’*, Ahi, Bigeye)
  • Marlin
  • Gulf Tilefish
  • Tilefish (Golden snapper)
  • Orange Roughy
  • Atlantic Halibut
  • Oysters (Gulf Coast)
  • Lingcod
  • Scorpionfish
  • Sea bass*
  • Freshwater Bass
  • Grouper*
  • Pacific Croaker
  • American Lobster
  • Bluefish*
  • Sablefish (black cod)

Please note this is not an exhaustive list.

Fish relatively Moderate in Mercury

The following fish are considered neither high or low in Mercury. Their Mercury content is average or moderate and their Mercury levels should be considered when incorporating them into your diet. You are considered to be generally safe to eat up to six 6-ounce servings each month.

  • Haddock
  • Pacific Mackerel
  • Smelt
  • Atlantic Tilefish
  • Canned light Tuna, such as ‘skipback tuna’
  • Cod (except ‘black cod’)
  • Spiny Lobster
  • Striped Bass
  • Black Bass
  • Saltwater Bass
  • Snapper
  • Lobster
  • Porgy
  • Sheepshead
  • Skate
  • Freshwater Perch
  • Hake
  • Monkfish
  • Mahi Mahi
  • Trout
  • Whitefish

Please note this is not an exhaustive list.

Fish relatively Low in Mercury

Luckily for me many of the fish lighter in Mercury are my favourites (massive salmon lover-evidence on my Instagram), but there are some other fish/seafood lower in Mercury that I am yet to try. Low Mercury fish are excellent choices for pregnant women, or those nursing and children. The FDA recommends up to 12 ounces of low Mercury fish per week if you’re pregnant or nursing.


Check them out below:

  • Catfish
  • (Wild) Salmon
  • Pollock
  • Shrimp
  • Crabs
  • Oysters
  • Mussels
  • Crayfish
  • Clams
  • Atlantic Mackerel
  • Tilapia
  • Flounder
  • Scallops
  • Freshwater Trout
  • Anchovies
  • Herring
  • Shad
  • Plaice
  • Pike
  • Butterfish
  • Squid
  • Atlantic Croaker
  • Sardines
  • Ocean Perch
  • Mullet
  • Sole

Please note this is not an exhaustive list.

Even though these fish are considered low in mercury, you may still want to limit your consumption of them to further prevent the accumulation of Mercury in your body. Generally, the FDA considers the risks of Mercury in fish far outweigh the benefits of eating them, especially in the case of low Mercury fish.

I will continue to eat fish lower in Mercury, and eat other foods, such as eggs and spinach, which are high in the selenium to help combat the effects of Mercury.

Comment your thoughts below. I would love to see whether reading this post has had an effect on what seafood (if any) you will will be eating in future.


Written by Robyn Elms

My aim is to help the world in any way I can. Awareness is the first step to positive change. That’s what I am trying to achieve with my blogs.

Stay Beautiful, Be Positive Peeps!


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