Nutrition Diet: What fish is not recommended to eat?

October 8, 2025 •

3 min read

According to the FDA, certain fish, including shark and swordfish, contain high levels of mercury and are listed as "Choices to Avoid" for vulnerable groups. Understanding what fish is not recommended to eat is crucial for a healthy and safe diet, ensuring you reap the benefits without the risks.

Quick Summary

This guide examines the fish species to avoid or limit due to high levels of mercury, environmental toxins, and unsustainable fishing practices. We explain why larger predatory fish pose a greater risk and provide safer, healthier alternatives for your dietary needs.

Key Points

Avoid High-Mercury Species: Steer clear of large predatory fish like shark, swordfish, king mackerel, and Gulf of Mexico tilefish due to very high mercury levels.
Risk to Vulnerable Groups: Pregnant women, breastfeeding mothers, and young children are most susceptible to mercury's harmful effects and should stick to the lowest-mercury options.
Beware of Biomagnification: Larger, older fish accumulate higher concentrations of mercury over their lifespan, making them a greater health risk.
Choose Sustainable Options: Consider environmental factors by avoiding fish like orange roughy, Chilean sea bass, and Atlantic bluefin tuna, which are often overfished.
Opt for Low-Mercury Alternatives: Healthy choices include salmon, sardines, shrimp, pollock, and canned light tuna, which are low in mercury and rich in nutrients.
Check Local Advisories: For fish caught in local rivers or lakes, consult local health or fishing advisories to check for specific contaminant warnings.

The Dangers of High-Mercury Fish and Other Contaminants

While fish is a valuable source of protein, omega-3 fatty acids, and essential vitamins, certain species can accumulate harmful contaminants. The most significant concern is mercury, particularly methylmercury, a potent neurotoxin that can damage the nervous system. This heavy metal enters waterways from natural sources and human activities, like industrial pollution, and is absorbed by aquatic life.

A key process behind dangerous mercury levels is biomagnification. As larger, predatory fish consume smaller fish and organisms, the mercury from their prey accumulates in their own tissues. This means species at the top of the aquatic food chain, which are often the largest and longest-lived, typically contain the highest concentrations of mercury. For this reason, vulnerable populations, including pregnant women, breastfeeding mothers, and young children, are advised to be especially cautious about their seafood choices. In addition to mercury, other environmental toxins like PCBs (polychlorinated biphenyls) and dioxins can be found in some fish, as can naturally occurring biotoxins that cause ciguatera and scombroid poisoning.

High-Mercury Fish to Avoid

Based on guidance from the FDA and EPA, several species should be avoided or significantly limited due to their high mercury content. These include larger, predatory fish that accumulate more mercury through their lifespan and diet.

Shark
Swordfish
King Mackerel
Tilefish (Gulf of Mexico)
Orange Roughy
Bigeye Tuna
Marlin

Sustainability and Contamination Concerns Beyond Mercury

Beyond mercury, other factors can make certain fish options less ideal for your diet, including concerns about unapproved antibiotics, poor farming practices, overfishing, and unsustainable methods that harm ecosystems. Fish to consider avoiding or limiting for these reasons include:

Imported Catfish and Pangasius (Swai/Basa)
Chilean Sea Bass (Patagonian Toothfish)
Atlantic Bluefin Tuna
Most Imported Farmed Shrimp

Choosing Safe and Healthy Seafood Alternatives

The key to a healthy diet that includes seafood is moderation and informed choices. Opt for smaller, lower-mercury fish and shellfish, and consider sustainability ratings from resources like the Monterey Bay Aquarium's Seafood Watch. Many excellent, low-mercury fish can be enjoyed regularly.

Here is a list of some of the "Best Choices" according to the FDA:

Salmon
Sardines
Anchovies
Catfish
Trout (freshwater)
Pollock
Atlantic Mackerel
Tilapia
Shrimp
Scallops
Clams

Fish Options Comparison


Fish Category	Example Species	Mercury Level	Sustainability Notes
Choices to Avoid	Shark, Swordfish, King Mackerel, Gulf of Mexico Tilefish, Bigeye Tuna, Orange Roughy, Marlin	Very High	Overfished, slow to reproduce, poor fishing methods
Good Choices (Limit to 1 serving/week)	Albacore/White Tuna (canned/frozen), Chilean Sea Bass, Grouper, Halibut	Moderate	Depends on species and catch method; some are vulnerable or have high bycatch
Best Choices (2-3 servings/week)	Salmon, Sardines, Canned Light Tuna, Catfish, Tilapia, Atlantic Mackerel, Shrimp, Pollock	Low	Generally more sustainable and lower risk, though farming methods can vary

Conclusion

While fish offers undeniable nutritional benefits, including heart-healthy omega-3s, a balanced diet requires awareness of potential risks. By understanding what fish is not recommended to eat, you can make informed decisions that protect your health and the environment. Prioritizing smaller, lower-mercury fish like salmon, sardines, and canned light tuna minimizes your exposure to harmful contaminants. For those with higher-risk profiles, such as pregnant women and children, adhering strictly to the "Best Choices" list is the safest course of action. Variety in your seafood consumption is also a smart strategy to avoid over-reliance on any single species. Always check local advisories for fish caught in your area, as contaminant levels can vary significantly. For comprehensive and regularly updated recommendations, consult resources from the FDA and reliable sources like Seafood Watch.

Frequently Asked Questions

Pregnant women should avoid shark, swordfish, king mackerel, and tilefish from the Gulf of Mexico due to high mercury content. It's recommended to eat 8–12 ounces per week of a variety of low-mercury fish, such as salmon or sardines.

Mercury levels are higher in some fish due to biomagnification, a process where contaminants accumulate up the food chain. Larger, older predatory fish consume smaller fish, inheriting and concentrating the mercury in their own bodies.

No. Canned light tuna (often skipjack) is a "Best Choice" with low mercury levels. However, albacore (white) tuna has more mercury, and large, predatory bigeye or ahi tuna have the highest levels and should be avoided, especially by vulnerable groups.

Symptoms of fish poisoning can include nausea, vomiting, abdominal pain, diarrhea, and tingling of the lips and tongue. Ciguatera poisoning can also cause neurological issues, while scombroid poisoning can cause a flushing or burning sensation.

For most adults, the Dietary Guidelines for Americans recommend eating at least 8 ounces of seafood per week. For pregnant or breastfeeding women, the recommendation is 8–12 ounces per week from the low-mercury "Best Choices" list.

No. Mercury is found throughout the muscle tissue of the fish, so cleaning or cooking it does not reduce the mercury content. The only way to limit mercury intake is to choose lower-mercury fish species.

Yes. Some fish, like Chilean sea bass or farmed shrimp from certain regions, are considered unsustainable due to overfishing or harmful farming practices, in addition to potential health risks. Always check sustainability guides for more specific information.