Fish can be a nutritious source of protein and healthy fats, but some species tend to contain higher levels of mercury or other contaminants than others. The best choice depends on the type of fish, where it was caught, and how often you eat it.

A more accurate approach than saying every fish on this list must be completely avoided is to limit or avoid the highest-contaminant choices, especially for people who are pregnant, breastfeeding, or young children.

1. Shark

Shark is a large, long-lived predator and can accumulate relatively high levels of mercury.

It is generally considered a fish to avoid or limit, particularly for people in groups more vulnerable to mercury exposure.

2. Swordfish

Swordfish can contain high levels of mercury because it is a large predatory fish.

Choosing lower-mercury seafood more often is generally recommended.

3. King Mackerel

King mackerel should not be confused with Atlantic mackerel. King mackerel is known for potentially high mercury levels.

4. Marlin

Marlin is another large predatory fish that may contain elevated mercury levels.

It is often recommended as a fish to avoid or limit.

5. Orange Roughy

Orange roughy is long-lived, which can allow contaminants such as mercury to accumulate over time.

6. Tilefish

Some types of tilefish can have particularly high mercury levels. The risk can also vary depending on where the fish was caught.

7. Bigeye Tuna

Not all tuna is the same. Bigeye tuna generally contains more mercury than lower-mercury canned “light” tuna.

Check the specific type rather than assuming all tuna has the same contamination risk.

8. Certain Types of Grouper

Mercury levels can vary between species and according to fish size and origin.

Some larger grouper may contain more mercury than smaller, short-lived fish.

9. Certain Types of Snapper

Contamination levels can vary by species and location. Larger fish may accumulate more mercury over time.

Local seafood advisories can provide useful information about fish caught in specific waters.

10. Escolar

Escolar is not primarily known for mercury. However, it contains naturally occurring wax esters that some people cannot digest well and may cause digestive problems.

This is a different concern from contamination but is worth knowing when choosing seafood.

11. Fish From Polluted Local Waters

Fish caught in contaminated lakes, rivers, or coastal waters may contain pollutants such as PCBs or other chemicals.

Always check local fish-consumption advisories if you catch your own fish.

12. Unknown or Poorly Labeled Seafood

Seafood that is improperly labeled or sold without clear information about its species and origin can make it difficult to assess potential risks.

Choose reputable sellers and look for clear labeling whenever possible.

🐟 Better Lower-Mercury Choices

Instead of avoiding fish altogether, consider lower-mercury options such as:

• Salmon
• Sardines
• Anchovies
• Trout
• Atlantic and Pacific mackerel (not king mackerel)
• Herring
• Pollock
• Cod

🛒 Smart Tips When Buying Fish

Know the Species

Names such as “mackerel” and “tuna” cover different species with different mercury levels.

Check the Origin

For locally caught fish, pay attention to official advisories for the specific body of water.

Buy From Reputable Sellers

Proper labeling and handling are important for food safety and informed choices.

Vary Your Seafood

Eating a variety of lower-mercury seafood can help reduce repeated exposure to the same contaminants.

The Bottom Line

The phrase “12 contaminated fish to avoid” can be misleading because contamination varies by species, size, origin, and location.

The most important concern for many shoppers is mercury, particularly in large, long-lived predatory fish. Rather than avoiding all seafood, choose a variety of lower-mercury fish and follow official local advisories when available.