swordfish fillet
Brittany Hambleton
Brittany Hambleton
March 26, 2024 ·  7 min read

14 Fish You Should Consider Never Eating

Fish can be an excellent part of a healthy diet, providing important nutrients like omega-3 fatty acids which can lower your risk for diseases like cardiovascular disease, cancer, Alzheimer’s and dementia, age-related macular degeneration, and rheumatoid arthritis, among others [1]. However, there are some fish you shouldn’t eat. Unfortunately, due to human industrial activity like coal-fired electricity generation, smelting, and the incineration of waste, large amounts of mercury are ending up in our waterways, and subsequently, the fish that swim in them. Once this mercury gets into the marine food chain, it “bioaccumulates.”

This means that as smaller fish get eaten by gradually larger fish, the concentration of mercury at each level becomes greater [2]. Consuming too much mercury can be dangerous to your health, and lead to mercury poisoning. For this reason, the US Food and Drug Administration (FDA) and the US Environmental Protection Agency (EPA) have issued guidelines regarding how much mercury is safe for humans to ingest, and the non-profit Environmental Defense Fund (EDF), provides suggestions for which fish you shouldn’t eat [2].

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1. Atlantic Cod

Atlantic Cod fish
Image Credit: Fishing Booker

The problem with Atlantic cod has less to do with your health, and everything to do with the environment and the fish population. Atlantic cod has been fished heavily for a thousand years, and in the late 1990s, the fishery collapsed. Fishing for Atlantic cod has been dramatically reduced since then, but the species has struggled to rebound. Scientists agree that the collapse of the fishery has fundamentally changed the North Atlantic food web, and the species is now considered vulnerable to extinction [3].

2. Atlantic Flatfish (halibut, flounder, and sole)

Atlantic Flatfish (halibut, flounder, and sole)
Image Credit: SFN

This is another case of overfishing and general waste. Commercial fisheries have what is referred to as “wasted bycatch”, which is when a fish or other marine species are caught unintentionally while catching other fish. US fisheries throw about 2 billion lbs of wasted bycatch overboard every year. This is equivalent to about half a billion meals! The California gillnet fishery, which targets halibut, has been identified as one of the worst, and if you’ve eaten halibut in the US it likely came from this operation [4].

3. Caviar

Fish Caviar
Image Credit: La Patiala

Caviar are the eggs of the Beluga Sturgeon, an ancient fish that can live for one hundred years. Its eggs are highly sought after and can be sold for thousands of dollars a pound. Because of this, this special fish is now highly vulnerable to extinction [5]. The same goes for many other types of Sturgeon as well.

4. Chilean Bass

Chilean Bass
Image Credit: Wine Knows Travel

In terms of the environment, this is another species that has been highly over-fished. In addition to that, its high mercury content poses a health risk to humans [6].

Read More: When Researchers Discovered an Underwater Volcanic Range it was Teeming With New Scary-looking Fish Species

5. Eel

Eel fish
Image Credit: Bradley’s Fish

This is one fish you may want to avoid on the sushi menu. Eels are slow to mature and have been overfished in many parts of the world, causing some populations to collapse. This is problematic because eels play an important role in spreading mussel populations, which act as natural water filters [7]. Additionally, eels absorb and store harmful chemicals and pollutants very easily. This is such a problem that in some areas residents are advised to eat eel no more than once per year [8].

6. Imported Basa, Swai, Tra, Striped Catfish

Imported Basa, Swai, Tra, Striped Catfish
Image Credit: vinmec

In many cases, these fish are simply labeled “catfish”, and should be avoided. A 2016 study found that seventy to eighty percent of these fish were contaminated by Vibrio Bacteria, which is what causes most cases of shellfish poisoning [9].

7. Imported Farmed Shrimp

Imported Farmed Shrimp fish
Image Credit: The Fish Site

There are a number of pesticides that are used globally in shrimp production. All but one of them are banned in the United States. On top of that, these shrimps have often been treated with large quantities of antibiotics, and so any time you handle these raw shrimp you run the risk of being infected with antibiotic-resistant bacteria [19].

Read More: The Atlantic Ocean Could Be Swallowed by a Terrifying ‘Ring of Fire’

8. Imported King Crab

Imported King Crab
Image Credit: Crab Meat

Around three-quarters of all crab sold in the United States is imported from Russia, where unsustainable fishing practices are very common. Technically, the only crab that was caught in Alaska can be called “Alaskan King Crab.” However, mislabelling is incredibly common, so it is important to know where your crab is coming from. If it says “imported” and “Alaskan” on the label, something is amiss and you should stay away [10].

9. Orange Roughy

Orange Roughy fish
Image Credit: Chef’s Mandala

These fish can live for several decades and don’t typically reach sexual maturity until they’re at least twenty years old. They are another species that have been overfished, but because of their very slow reproduction cycles, they have an extremely difficult time recovering [11]. Orange Roughy is also known to have high levels of mercury [7].

10. Shark

Image Credit: Geographical

Since sharks are at the top of the food chain, they have very high levels of mercury [7]. They are also slow to mature and reproduce, and thus overfishing has depleted their populations as well.

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11. Atlantic Bluefin Tuna

Atlantic Bluefin Tuna fish
Image Credit: vox

Bluefin tuna have been severely overfished, and are now considered to be highly vulnerable to extinction [12]. They are also large predatory fish and thus contain high levels of mercury [7].

12. Swordfish

Image Credit: Shimano

Another predatory fish, mercury is the main concern here. In fact, the EDF has recommended that women and children avoid swordfish altogether and men consume it no more than once per month [13].

13. King Mackerel

King Mackerel and Spanish Mackerel fish
Image Credit: The Pete is On

Both King Mackerel and Spanish Mackerel have high levels of mercury and should be avoided, especially by women and children [7].

14. Grouper

Grouper fish
Image Credit: Katie’s Seafood

Grouper has moderately high mercury levels and is vulnerable to overfishing [7]. It is also often the target for seafood fraud. The “grouper” that is for sale is may actually be a cheaper form of fish that is being mislabeled. One study found that up to 87% of seafood like grouper, cod, and snapper may be mislabeled [14].

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A Note on The Role of Selenium in Mercury Toxicity

Source: WPCouncil.org

If you love fish but you are concerned about mercury toxicity, there is some good news for you- many of the fish that people routinely eat are high in selenium, which may play a role in preventing the absorption of excessive mercury [15]. Still, there is a caveat. This does not mean that you can eat as many high-mercury fish as you want. However, if you do choose to eat some fish that have a higher content of the heavy metal occasionally, co-consuming enough selenium may help to negate negative effects.
The core message here is this: If you’re eating high selenium fish that is low to moderately high in mercury, the overall risk is lower. If you’re consuming fish that is high in mercury but low in selenium (i.e. shark), it’s best to avoid or to consume very rarely.

Fish To Eat More Of

Atlantic mackerel (Scomber scombrus)
Image Credit: The Fish

This does not mean you have to give up fish altogether, but it highlights the importance of reading labels and knowing where your fish is coming from. Wild-caught Alaskan salmon, Pacific Sardines, and Atlantic mackerel are all high in omega-3s, as well as several other nutrients, and have less of a negative impact on the environment. Other good choices include Albacore tuna that was caught in the US or Canada, Alaska Cod, Arctic Char, Rainbow Trout, among others. The EDF Seafood Selector provides a comprehensive list of the best seafood and fish to eat, including where it should come from and how it should be produced.

The Bottom Line

Variety of seafood
Image Credit: Metro

When you’re choosing which foods to eat, it is important not only to consider the impact that those foods will have on your health but also the impact that they’re having on the planet. It is crucial that we as consumers make responsible choices to ensure that our planet- and all the organisms upon it- continue to thrive for future generations.

Read More: Discover the Upside-Down Lakes and Waterfalls at the Bottom of the Ocean


  1. Omega-3 Fatty Acids.” ODS
  2. How Does Mercury Get Into Fish?Scientific American. December 30, 2011.
  3. Atlantic Cod.” Oceana
  4. Why 500 Million U.S. Seafood Meals Get Dumped In The Sea.” NPR. Alastair Bland. March 21, 2014.
  5. Beluga Sturgeon.” Oceana
  6. Mercury Levels in Commercial Fish and Shellfish (1990-2012).” FDA
  7. “”The American Eel (Anguilla rostrata) – An Under-Appreciated Resident and Important Link to the Health of the Delaware River.” DelawareRiver.
  8. New Jersey River Polluters Fund Toxic Fish Swap — But There’s A Snag.” NPR. Sarah Gonzalez. January 26, 2016.
  9. Microbiological and chemical safety concerns regarding frozen fillets obtained from Pangasius sutchi and Nile tilapia exported to European countries.” PubMed. Piotr Kulawik, et al. March 2016.
  10. Golden King Crab.” Fish Choice
  11. Orange Roughy.” Oceana
  12. Atlantic Bluefin Tuna.” Oceana
  13. SWORDFISH.” Seafood
  14. “Grouper, snapper, cod? Mislabeling is rampant in the seafood industry” CBS News. Oct, 20, 2021.
  15. Selenium and mercury in pelagic fish in the central north pacific near Hawaii.” PubMed. J John Kaneko , Nicholas V C Ralston. December 2007.

    Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.