Fish You Should Avoid Eating – And Why

Fish provide essential nutrients like omega-3 fatty acids, which help lower the risk of cancer, Alzheimer’s, heart disease, and more. However, not all fish are safe to eat. Mercury pollution from industrial activities contaminates waterways, and as smaller fish get eaten by larger fish, mercury levels increase. Consuming too much mercury can lead to poisoning, making it crucial to choose fish wisely.

Regulatory bodies like the FDA, EPA, and Environmental Defense Fund (EDF) have issued guidelines on fish safety. Below are some species you should avoid.

1. Tilapia – Worse Than Bacon?

Tilapia is one of the most consumed fish in the U.S., but researchers warn that it contains low omega-3 levels and high inflammatory omega-6 fatty acids. Chronic inflammation is linked to heart disease, cancer, and diabetes. If you eat tilapia, avoid imports from China, where farming practices are concerning. The best sources include the U.S., Canada, the Netherlands, Ecuador, and Peru. Wild-caught tilapia is better but hard to find.

2. Atlantic Cod – A Species in Trouble

Centuries of overfishing led to the collapse of the Atlantic cod fishery in the 1990s. Though fishing has decreased, the population struggles to recover. Experts say this collapse has disrupted the North Atlantic food web, and the species now faces extinction.

3. Atlantic Flatfish (Halibut, Flounder, Sole) – Victims of Wasteful Fishing

Overfishing and wasted bycatch plague this species. U.S. fisheries discard around 2 billion pounds of bycatch yearly—wasting what could be half a billion meals. The California gillnet fishery, known for targeting halibut, ranks among the worst offenders.

4. Caviar – The Cost of Luxury

Caviar comes from the Beluga Sturgeon, a fish that can live for 100 years. Due to high demand, this species and many other sturgeon face extinction.

5. Chilean Sea Bass – High in Mercury

This fish contains dangerous mercury levels, making it unsafe for frequent consumption.

6. Eel – Full of Toxins

Eels mature slowly and have been overfished. They play a vital role in spreading mussels, which filter water naturally. Worse, eels easily absorb pollutants, prompting some regions to recommend eating them no more than once per year.

7. Imported Catfish (Basa, Swai, Tra, Striped Catfish) – Bacteria Risk

Often mislabeled as “catfish,” these fish frequently contain Vibrio bacteria, which cause shellfish poisoning. A 2016 study found 70-80% of these fish were contaminated.

8. Imported Farmed Shrimp – Pesticides and Antibiotics

Most pesticides used in shrimp farming are banned in the U.S. These shrimp also receive heavy doses of antibiotics, increasing the risk of exposure to antibiotic-resistant bacteria when handled raw.

9. Imported King Crab – Know Your Source

Around 75% of crab sold in the U.S. comes from Russia, where overfishing is common. Only crab caught in Alaska qualifies as “Alaskan King Crab,” but mislabeling is rampant. If a label says both “imported” and “Alaskan,” it’s likely fake.

10. Orange Roughy – Slow Reproduction, High Mercury

This fish can live for decades but doesn’t reach sexual maturity until 20 years old. Overfishing has depleted its population, and its slow reproduction rate makes recovery difficult. It also contains high mercury levels.

11. Shark – Mercury and Overfishing

Sharks have dangerously high mercury levels. Slow to mature and reproduce, they suffer from overfishing, further endangering their populations.

12. Atlantic Bluefin Tuna – A Species at Risk

Highly vulnerable to extinction, Bluefin tuna are also top predators, meaning they accumulate high mercury levels.

13. Swordfish – Too Much Mercury

Due to its high mercury content, the EDF advises women and children to avoid swordfish completely, while men should eat it no more than once per month.

14. King Mackerel – Another Mercury Concern

Both King Mackerel and Spanish Mackerel contain high mercury levels. Women and children should avoid them.

15. Grouper – Mercury and Seafood Fraud

Grouper has moderately high mercury levels and is overfished. It’s also a frequent target of seafood fraud—up to 87% of samples tested in one study were mislabeled, with cheaper fish sold as grouper.

Can Selenium Reduce Mercury Risks?

Some fish contain selenium, which may help prevent mercury absorption. However, this doesn’t mean you can eat high-mercury fish without risk. If a fish has high mercury but low selenium (like shark), it’s best to avoid it.

Better Fish Choices

You don’t have to give up fish entirely—just choose wisely. Some of the best options include:
✔ Wild-Caught Alaskan Salmon
✔ Pacific Sardines
✔ Atlantic Mackerel
✔ U.S. or Canadian-Caught Albacore Tuna
✔ Alaska Cod
✔ Arctic Char
✔ Rainbow Trout

For a comprehensive list of safe seafood options, the EDF Seafood Selector provides guidelines on sustainability and safety.