7 Types of Fish High in Mercury: Limit Them No Matter How Much You Like Them

Consuming too much of these fish can damage the brain, kidneys, and even increase the risk of cancer.

Fish have long been considered a “golden food” thanks to their richness in protein and omega-3 fatty acids, which benefit the heart and brain. However, not all fish are safe for frequent consumption. Some species contain high levels of mercury, which—if consumed excessively—can cause serious health problems such as neurological damage, impaired kidney function, and even higher cancer risk.

In fetuses and young children, mercury poisoning can lead to severe conditions such as cerebral palsy, blindness, deafness, intellectual disability, respiratory disorders, and abnormal growth.

According to Very Well Fit, the larger and longer a fish lives, the higher its mercury accumulation tends to be.

7 Fish High in Mercury

Business Insider has listed the 7 fish with the highest mercury content:

1. King Mackerel
According to the U.S. Food and Drug Administration (FDA), king mackerel is a medium-sized fish with rich flavor but high mercury levels. However, not all mackerel species are the same—Atlantic mackerel, for instance, has low mercury levels and is considered a safer alternative.

2. Marlin
Also known as blue marlin, this large predatory fish consumes many smaller fish, making it more likely to accumulate mercury from its prey. As a result, marlin often contains high levels of mercury.

3. Orange Roughy
Orange roughy has an exceptionally long lifespan—up to 149 years. The longer it lives, the more mercury it accumulates in its body.

4. Shark
As an apex predator, shark easily accumulates mercury from smaller fish. A 2011 study in New Jersey (USA) found mercury levels in shark to be 2–6 times higher than the recommended maximum limit for human consumption.

5. Swordfish
Although highly popular, swordfish is among the fish species that should be limited due to its high mercury content.

6. Tilefish
The FDA has issued warnings that tilefish is one of the fish species containing very high levels of mercury.

7. Bigeye Tuna
Bigeye tuna is one of the tuna species with the highest mercury levels. The FDA lists bigeye tuna as a fish to limit, especially for children and pregnant women. In contrast, skipjack tuna has lower mercury levels and is considered safer to eat.

Expert Recommendations

Nutritionists recommend consuming at least two servings of fish per week—about 340 g in total. However, one should be cautious with mercury-rich species and prioritize low-mercury, omega-3-rich fish such as salmon, sardines, herring, and Atlantic mackerel.

Pregnant or breastfeeding women should eat only 2–3 servings per week, with a total not exceeding 340 g, and should strictly avoid the 7 high-mercury fish listed above. If catching fish from rivers, lakes, or local seas, it is essential to check safety advisories from environmental authorities before consuming.