14 Fish You Should Be Cautious About Eating

Fish are a cornerstone of a healthy diet, offering omega-3 fatty acids, high-quality protein, and essential vitamins and minerals.

Regular fish consumption can reduce the risk of heart disease, Alzheimer’s, cancer, dementia, age-related macular degeneration, and rheumatoid arthritis. However, not all fish are created equal. Certain species carry high levels of mercury or are caught using unsustainable practices, making them risky for both your health and the environment.

Mercury, a heavy metal released from industrial activities such as coal-fired power generation, smelting, and waste incineration, accumulates in waterways and gradually builds up in marine life. This process, known as bioaccumulation, means larger predatory fish can carry dangerously high mercury concentrations. Long-term exposure can lead to mercury poisoning, with symptoms ranging from cognitive impairment to cardiovascular issues.

The US Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) provide guidance on safe mercury consumption, while the Environmental Defense Fund (EDF) lists fish that should be avoided.

Here’s a detailed guide on 14 fish you should consider never eating, along with safer alternatives.

1. Tilapia

Tilapia is one of the most widely consumed fish in the United States, but it may contribute to inflammation rather than providing health benefits. Research from Wake Forest University and studies published in the Journal of the American Dietetic Association indicate that tilapia contains very low levels of beneficial omega-3s and unusually high amounts of inflammatory omega-6 fatty acids.

Why it’s risky:

• High omega-6 levels can worsen chronic inflammation.

• May aggravate autoimmune disorders or contribute to heart disease, diabetes, and cancer.

Tips if you eat tilapia:

• Avoid tilapia from China due to questionable farming practices.

• Prefer wild-caught tilapia or sources from the U.S., Canada, Netherlands, Ecuador, and Peru.

2. Atlantic Cod

Atlantic cod is a classic seafood staple, but overfishing has caused its population to collapse. Although fishing has decreased, recovery has been slow, and the species is now classified as vulnerable to extinction.

Environmental concern:

• Decades of overfishing disrupted the North Atlantic food web.

• Consuming Atlantic cod contributes indirectly to unsustainable fishing practices.

3. Atlantic Flatfish (Halibut, Flounder, Sole)

These fish are often affected by wasted bycatch, which occurs when non-target marine species are accidentally caught and discarded. U.S. fisheries discard roughly 2 billion pounds (907,000 metric tons) of bycatch annually, equivalent to half a billion meals.

Specific issues:

• California gillnet fisheries targeting halibut are notable offenders.

• Eating these fish supports practices that damage marine ecosystems.

4. Caviar

Caviar comes from sturgeon, primarily the Beluga Sturgeon, which can live up to 100 years. High demand has pushed the species toward extinction, with other sturgeon species similarly at risk.

Why it matters:

• Harvesting caviar threatens ancient fish populations.

• Conservation experts advise avoiding caviar unless it’s certified sustainable.

5. Chilean Bass

Chilean bass is a high-mercury fish, posing a health risk, particularly for pregnant women, children, and frequent seafood consumers. Mercury can impair neurological development in children and contribute to long-term health issues in adults.

6. Eel

Eels are slow-growing, overfished in many regions, and play a key role in aquatic ecosystems by spreading mussels that filter water naturally. They also absorb toxins and pollutants readily.

Consumption caution:

• Residents in some regions are advised to eat eel no more than once per year.

7. Imported Basa, Swai, Tra, Striped Catfish

These imported fish are often mislabeled simply as “catfish.” Studies show that 70–80% of these fish were contaminated with Vibrio bacteria, which can cause serious shellfish-related illnesses.

Avoidance tip:

• Choose domestically farmed catfish or certified seafood to reduce exposure.

8. Imported Farmed Shrimp

Imported farmed shrimp may be treated with pesticides banned in the U.S. and high doses of antibiotics, creating risks of antibiotic-resistant bacteria. Handling raw shrimp from unknown sources can also cause infection.

Safer alternative:

• Look for U.S.-sourced shrimp or products with transparent farm certifications.

9. Imported King Crab

Most crab sold in the U.S. is imported from Russia, where unsustainable practices are common. Labels claiming “Alaskan King Crab” may be misleading.

Tip:

• Only trust crab explicitly caught in Alaska with verifiable certification.

10. Orange Roughy

Orange roughy can live for up to 150 years and matures sexually around 20 years of age, making it highly vulnerable to overfishing. Mercury levels are also elevated, posing additional health risks.

11. Shark

Sharks are top predators, slow to mature, and often overfished, leading to population declines. They also carry very high mercury levels, making them unsafe for regular consumption.

12. Atlantic Bluefin Tuna

Bluefin tuna populations are now highly vulnerable to extinction. As large predatory fish, they also accumulate mercury, making them a double risk for both health and sustainability.

13. Swordfish

Swordfish contain high mercury levels. Guidelines suggest that women and children avoid it entirely, while men consume it no more than once per month.

14. King and Spanish Mackerel

Both mackerel types have high mercury content. They should be avoided, especially by pregnant women and children.

15. Grouper

Grouper faces overfishing threats and often suffers from seafood mislabeling, with cheaper fish sold under its name. Studies found up to 87% of grouper, cod, and snapper may be mislabeled.

Selenium and Mercury: A Balancing Act

If you enjoy seafood but worry about mercury, selenium-rich fish can help reduce mercury absorption. Fish with high selenium and low-to-moderate mercury levels are safer. However, consuming high-mercury, low-selenium species like shark should be rare or avoided.

Fish You Can Eat Safely

You don’t need to give up seafood entirely. Healthier choices include:

• Wild-caught Alaskan Salmon (rich in omega-3s)

• Pacific Sardines

• Atlantic Mackerel

• Albacore Tuna (U.S./Canada-caught)

• Alaska Cod

• Arctic Char

• Rainbow Trout

These options provide nutritional benefits, lower mercury exposure, and a smaller environmental impact. For a comprehensive list of safe seafood, refer to the EDF Seafood Selector.

Just that.