12 Unhealthy Fish to Avoid: What Not to Order and What to Eat Instead

Many popular catches carry hidden toxins and push vulnerable species toward collapse.

By Medha deb

Created on Sep 24, 2025

Many popular catches carry hidden toxins and push vulnerable species toward collapse.

Fish is often considered a smart dietary choice, thanks to its lean protein content and omega-3 fatty acids. However, not all fish are equally beneficial – some are tainted by unsafe levels of contaminants, suffer from sustainability issues, or are linked to questionable farming practices. This guide explores the twelve fish varieties you should steer clear of and offers healthier, more sustainable alternatives for your plate.

What Makes Some Fish Unhealthy?

Contamination: High levels of mercury, polychlorinated biphenyls (PCBs), and other pollutants can pose serious health risks.
Overfishing: Many species are being pushed to the brink of extinction, undermining marine ecosystems and future fish stocks.
Questionable Farming Techniques: Some farmed fish are exposed to overcrowded pens, antibiotics, and pesticides, raising both environmental and health concerns.
Seafood Fraud: Mislabeling and substitution can cause consumers to unknowingly eat less sustainable or more contaminated species.

Fish to Avoid—and Why

1. Tilapia (Farmed)
Why it’s bad: Farmed tilapia, especially from China, often contains elevated levels of inflammatory omega-6 fatty acids and very low omega-3s. In addition to poor nutrition, farming practices may involve the use of substandard feeds and antibiotics.
- Low omega-3 fatty acid content, high omega-6 fatty acid levels.
- Risk of inflammatory health effects.
- Questionable farming standards in some countries.
Eat this instead: Seek out wild-caught tilapia (rare), or opt for U.S., Canadian, or Peruvian farmed tilapia, or choose mild domestically farmed catfish for a similar taste.
2. Caviar (Beluga and Wild Sturgeon)
Why it’s bad: Beluga caviar and caviar from wild-caught sturgeon are endangered due to overfishing and water pollution from dam building. These fish take years to mature, making their populations slow to recover.
- Overfishing jeopardizes species’ survival.
- Habitat disruption from dams and pollution.
Eat this instead: Try American Lake Sturgeon or Hackleback/Shovelnose Sturgeon caviar from the Mississippi River system. These are more sustainable choices.
3. Atlantic Cod
Why it’s bad: Decades of overfishing have devastated Atlantic cod stocks, leaving them precariously close to extinction. Management failures have worsened their situation.
- Population collapsed, listed as threatened.
- Critical for marine food webs and local economies.
Eat this instead: Pacific cod stocks are healthy and sustainable. Also consider eco-friendly white-fleshed fish from domestic sources.
4. American Eel
Why it’s bad: Known as yellow or silver eel, this sushi staple is highly contaminated with PCBs and mercury. Fisheries are hurt by pollution and overharvesting.
- PCBs and mercury pose health risks.
- Fisheries negatively impacted by pollution and overexploitation.
Eat this instead: Atlantic or Pacific-caught squid is a safer alternative for eel lovers looking for a similar texture and flavor.
5. Imported Shrimp
Why it’s bad: The dirtiest of the “dirty dozen,” imported farmed shrimp is rife with antibiotics, chemical residues, and contaminants including insect fragments and rat hair. Less than 2% of imported seafood is inspected prior to sale in the U.S.
- 90% of U.S. shrimp is imported.
- Linked to E. coli, filth, and harmful residues.
- Minimal government inspection.
Eat this instead: Choose domestic shrimp, ideally from the Gulf of Mexico or pink shrimp certified from Oregon.
6. Atlantic Flatfish (Flounder, Sole, Halibut)
Why it’s bad: Heavily contaminated due to centuries of overfishing, Atlantic flatfish populations are as low as 1% of sustainable levels.
- Extremely low population numbers.
- High contamination risk.
Eat this instead: Pacific halibut remains a sustainable choice, as does domestically farmed catfish or tilapia for a similar mild flavor.
7. Atlantic Salmon (Wild-Caught and Farmed)
Why it’s bad: Wild Atlantic salmon are so scarce that commercial fishing is illegal. Farmed salmon cause environmental damage due to crowded conditions, disease, and the use of antibiotics and pesticides. Escapees threaten native populations.
- Farmed salmon pens pollute and spread disease.
- Risk of antibiotics and pesticide residues.
- Illegal to catch wild Atlantic salmon due to low stocks.
Eat this instead: Opt for wild-caught Alaskan salmon, which are well managed and less contaminated.
8. Imported Catfish (Vietnamese Pangasius)
Why it’s bad: Pangasius (often sold as catfish or basa) is imported mainly from Vietnam, where it may be contaminated by antibiotics and environmental pollutants.
- Risk of antibiotic contamination.
- Environmental pollution from farming practices.
Eat this instead: U.S.-farmed catfish is subject to stricter regulations and is a safer, more sustainable choice.
9. Atlantic Bluefin Tuna
Why it’s bad: Overfished nearly to extinction, Atlantic bluefin tuna is also a large predatory species that accumulates high levels of mercury.
- Population at just 2.6% of historic levels.
- High mercury content poses health risks.
- Targeted fisheries threaten the species further.
Eat this instead: Skipjack tuna caught by Pacific troll or pole methods is a more sustainable sushi option.
10. Swordfish
Why it’s bad: Swordfish has high mercury levels; women and children are advised to avoid it completely, while men should limit to one serving per month.
- Mercury contamination is dangerous, especially for vulnerable groups.
- Predatory fish bioaccumulate toxins.
Eat this instead: If you crave firm, meaty fish, consider Pacific-caught albacore tuna, which is lower in mercury and more sustainably managed.
11. King Mackerel
Why it’s bad: Another high-mercury fish, king mackerel is off limits for women and children. Spanish mackerel also shows elevated mercury levels.
- FDA advises avoidance for at-risk populations.
- Health risk due to mercury contamination.
Eat this instead: Atlantic mackerel is lower in mercury and considered a healthy, sustainable seafood option.
12. Grouper
Why it’s bad: Grouper contains moderately high mercury and faces overfishing threats. It’s also subject to frequent seafood fraud, with cheaper fish sold as grouper.
- Mercury contamination and overfishing risks.
- Commonly mislabeled, leading to seafood fraud.
Eat this instead: Opt for U.S.-sourced black sea bass or Pacific rockfish for a similar texture with lower contamination risk.

Summary Table: Fish to Avoid & Better Alternatives

Fish to Avoid	Main Issue	Recommended Alternative
Tilapia (Farmed, China)	Low omega-3, high omega-6, questionable farming	Wild/U.S./Canadian tilapia, domestic catfish
Beluga Caviar/Sturgeon	Overfishing, pollution, slow maturation	American sturgeon caviar
Atlantic Cod	Overfishing, threatened status	Pacific Cod
American Eel	Contaminants: PCBs, mercury	Squid (Atlantic/Pacific-caught)
Imported Shrimp	Antibiotics, chemicals, poor inspection	Domestic Gulf/Pink shrimp
Atlantic Flatfish	Heavy contamination, very low stock	Pacific Halibut, farmed U.S. catfish
Atlantic Salmon	Illegal fishing, farming pollution	Wild Alaskan salmon
Imported Catfish (Pangasius)	Antibiotics, environmental pollution	U.S. Farmed Catfish
Atlantic Bluefin Tuna	Overfishing, high mercury	Pacific Skipjack Tuna
Swordfish	High mercury	Pacific Albacore Tuna
King Mackerel	High mercury	Atlantic Mackerel
Grouper	Mercury, overfishing, seafood fraud	Black Sea Bass, Pacific Rockfish

Frequently Asked Questions (FAQs)

Q: Is all farmed fish unhealthy?

A: Not all farmed fish are unhealthy. The risk depends on the species, origin, and farming practices. Domestically farmed fish often follow stricter standards and may be safer, while imported farmed fish (from countries with less oversight) may be contaminated.

Q: How can I find out if my seafood is sustainably sourced?

A: Look for certifications such as the Marine Stewardship Council (MSC) or the Best Aquaculture Practices (BAP) label. Ask your fishmonger or read package details for source information.

Q: Are mercury levels dangerous in fish?

A: Mercury is especially harmful for pregnant women, nursing mothers, and children. In adults, excessive mercury may impact neurological health. Stick to small fish lower on the food chain to minimize exposure.

Q: What fish are both healthy and eco-friendly?

A: Good options include wild-caught Alaskan salmon, sardines, Atlantic mackerel, U.S. farmed catfish, and Pacific halibut. These species are typically lower in contaminants and managed sustainably.

Q: Why does seafood fraud occur?

A: Some fish are replaced with cheaper alternatives for profit, or to keep up with high demand when supply is low. This deception can give consumers unintended exposure to contaminants or unsustainable species.

Additional Tips for Safe Seafood Choices

Choose smaller, non-predatory fish, which generally accumulate fewer toxins.
Favor wild-caught options when possible, especially from well-managed U.S. or Canadian fisheries.
Check seafood guides from organizations such as Seafood Watch for current recommendations based on region and season.
Ask your server or fishmonger about the catch’s origin and handling practices.

Conclusion: Choose Fish Wisely—For Your Health and the Planet

Being an informed consumer means making choices that prioritize both personal health and environmental sustainability. Avoiding these twelve fish varieties helps reduce your exposure to contaminants and lightens the burden on threatened marine species. By opting for recommended alternatives, you increase your well-being and support responsible fishing and farming methods for future generations.

References

Author

medha deb

Medha Deb is an editor with a master's degree in Applied Linguistics from the University of Hyderabad. She believes that her qualification has helped her develop a deep understanding of language and its application in various contexts.

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