Which Fish Are Highest in Mercury

Which Fish Are Highest in Mercury

Fish are the best source of omega-3 proteins, nutrients like iron and potassium, and B vitamins. Additionally, fish are believed to be anti-aging foods.

However, eating the wrong fish can lead to high mercury levels in the body. Due to this fear, many people ask which fish are highest in mercury?

Most seafood is already contaminated with high mercury levels. And for this reason, you should take modern nutrition with extra seriousness. Else, we all suffer incurable diseases.

How Fish Ingests Mercury

blue and orange tang fish

Mercury is a natural chemical element found in the soil, water, and air. However, modern industrialization and other technologies have led to increased mercury levels in our environment.

For that reason, pollution-free water bodies and the atmosphere are a thing of the past. Mercury is released into the environment daily by;

  • Burning coal
  • Burning oil
  • Burning natural gas
  • Medical wastes
  • Forest fires

When all this happens, at last, it rains, and all the mercury elements are swept into the rivers and later into the oceans, seas, and lakes.

Once the mercury elements settle into the large water bodies, they are absorbed into fish tissues through gills or digestive tracts.

Why Mercury is Hazardous to Human Health

Since mercury is released into the environment daily, all fish have traces of mercury. You need to know which fish are highest in mercury because mercury isn’t good for your health.

According to the Journal of Preventive Medicine and Public Health’s 2012 study, mercury can affect the brain by damaging the central nervous system. An earlier study in the same year revealed that mercury could also cause heart disease.

There are three types of mercury;

  • Organic
  • Inorganic
  • Metallic (Elemental)

Methylmercury, found in the organic type, is the most toxic in the human body. It can turn into liquid at room temperature, therefore easily ingestible.

According to US Food and Drug Administration, pregnant and breastfeeding women and children are more prone to Methylmercury. For this reason, they warned them against feeding on high mercury fish.

Methylmercury is proven to damage the brains of unborn babies and infants, which causes neurological and behavioral issues like;

  • Mood swings
  • Anxiety
  • Memory loss
  • Anxiety
  • Vision impairment
  • Breathing complications
  • Muscle weakening

Additionally, methylmercury increases the production of free radicals in the body and reduces antioxidants which brings oxidative stress.

Read: How do you treat tap water for fish?

silver fishes underwater

How to Avoid too Much Mercury

The first trick you can master to identify less mercury fish is observing the size. Smaller fish contain less mercury compared to predator fish. Further, the longer the fish’s lifespan, the more mercury level it has in its tissues.

Secondly, lower your fish consumption to at least once or twice a week.

Third, know the types of fish that contain higher mercury levels. If possible, minimize consuming their meat to preserve your health.

Which Fish Are Highest in Mercury

Consuming fish with more than 0.5 ppm mercury level may cause health problems. Check on the table below;

 Fish TypeMercury Level in Parts Per Million
1.King Mackerel0.73 ppm
2.Bigeye Tuna0.689 ppm
3.Orange Roughy0.571 ppm
4.Shark0.96 ppm
5.Sword Fish0.995 ppm
6.Tile Fish1.45 ppm

King Mackerel

King mackerel fish is a migratory species usually found in the Gulf of Mexico and the Atlantic Ocean. The fish is medium-sized and can weigh from 5 to 14 kilograms. However, some are reported to exceed 40 kilograms.

Their external bodies are covered with loosely attached scales. King mackerels are carnivorous since they feed on smaller fish.

Read: When to euthanize a betta fish humanely

shallow focus photo of green fish

Bigeye Tuna

Bigeye tuna belongs to the large mackerel family. They are usually found in open waters of tropical and temperate oceans.

The fish can grow up to 8 feet and weighs up to 180 kilograms. They have deep and streamlined bodies with big heads and eyes. Like the king mackerel, they feed on other smaller fish like the crustaceans.

Orange Roughy

Also known as red roughy, they are deep-sea fish. They are popularly recognized for their long lifespan of over 200 years. This long lifespan causes their tissues to carry higher levels of mercury. They are slow in growth and late to maturity.

See also: How much do piranhas cost?


According to a fossil study, sharks existed 400 million years ago. They are fish, even though many people refer to them as mammals. Sharks are found in nearly all deep seas, and they are of different sizes.

The largest is a whale shark around 12 meters in length.

Sword Fish

Sword fish is large and highly migratory. They are well recognized for their long, flat, and pointed bills. These predatory fish have elongated and rough bodies.

You’ll easily find swordfish in tropical and temperate areas of the Indian Ocean, Pacific Ocean, and Atlantic Ocean.

Usually, they are found near the water surface, and they can grow to 10 feet in length. The heaviest reported swordfish weighed around 650 kilograms.

Read: How to get air bubbles out of fish tank

Tile Fish

They are small marine fish you’ll mostly find in sandy areas. The US Food and Drug Administration pointed out the tilefish as one of the highest mercury fish. As such, they warned pregnant and breastfeeding mothers from consuming them.

Tilefish length can range up to 4.3 inches. On the other hand, they love temperate and tropical areas of the Indian Ocean, Atlantic Ocean, and Pacific Ocean.

FAQs on Which Fish are Highest in Mercury

Which Fish Has Least Mercury?

Although most predatory fish are high in mercury, small fish categories have low mercury safe for consumption.

Here is the list of five common fish with low mercury;
– Salmon
– Pollock
– Catfish
– Shrimp; and
– Canned light tuna

What is the Healthiest Fish to Eat?

Salmon is one of the best sources of omega-3 proteins. Eating salmon regularly can keep your body free from omega 3 deficiency since it isn’t capable of making omega 3s on its own.

How Do You Rid Your Body of Mercury?

Mercury is eliminated from the body through urine. As such, drinking a lot of water can speed up the process. Unfortunately, some mercury elements can be lethal, and the best way is to avoid them. One of the ways to avoid this is to know which fish are highest in mercury.

Read: Why is salmon low in mercury?


State Government of Victoria: Mercury in fish

U.S Food and Drug Administration: Mercury Levels in Commercial Fish and Shellfish (1990-2012)

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