Which sea fish has the most mercury?

According to the U.S. Food and Drug Administration (FDA), methylmercury levels in tilefish from the Gulf of Mexico average 1.123 parts per million (ppm), making it the sea fish with the highest average mercury concentration. This is because larger, longer-lived predatory fish accumulate more mercury through bioaccumulation, posing a health risk to consumers.

Quick Summary

This guide reveals the sea fish species with the highest mercury levels, explaining the process of bioaccumulation in marine life. It details which fish the FDA recommends avoiding and provides information on safer, lower-mercury alternatives for a healthier diet.

Key Points

• Tilefish (Gulf of Mexico) is Highest: Tilefish from the Gulf of Mexico has the highest average mercury levels among sea fish, according to FDA data.

• Large Predators Accumulate More Mercury: Fish higher up the food chain, such as shark and swordfish, accumulate more methylmercury through bioaccumulation over their long lifespans.

• Avoid Top Predators: The FDA and EPA advise against eating shark, swordfish, king mackerel, and Gulf of Mexico tilefish due to their high mercury content.

• Opt for Low-Mercury Choices: Safe seafood options include salmon, shrimp, sardines, and canned light tuna, which are lower on the food chain.

• Mercury is Stored in Tissue: Cooking or removing the skin does not reduce mercury, as it is embedded in the fish's muscle tissue.

• Specific Groups Need Caution: Pregnant women, nursing mothers, and young children should be especially careful about limiting their intake of higher-mercury fish.

Why Large Predatory Fish Have Higher Mercury Levels

Mercury is a naturally occurring element that enters the oceans from both natural events, like volcanic eruptions, and human activities, such as industrial waste and coal-burning power plants. In aquatic ecosystems, bacteria convert this mercury into a highly toxic organic compound called methylmercury. This methylmercury enters the food chain when it is absorbed by algae, which are then consumed by smaller fish.

Larger, predatory fish, such as shark, king mackerel, and swordfish, are at the top of the marine food chain and consume many of these smaller fish. Because fish absorb methylmercury but excrete it very slowly, the toxin accumulates in their muscle tissue over their lifespan, a process known as bioaccumulation and biomagnification. This explains why fish that are both long-lived and high on the food chain consistently have the highest concentrations of mercury.

The Fish with the Highest Mercury Content

The U.S. Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) have identified several species that contain the highest levels of mercury and should be avoided, particularly by sensitive groups like pregnant women and young children. These include:

Highest Mercury Species (Choices to Avoid):

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

Comparing Mercury Levels in Common Seafood

It's helpful to compare mercury levels to make informed choices. The table below shows average mercury levels and FDA/EPA recommendations for various seafood types:

Seafood Species	Average Mercury (ppm)	FDA/EPA Recommendation	Why?
Tilefish (Gulf of Mexico)	1.123	Choices to Avoid	Top of food chain, long lifespan.
Swordfish	0.995	Choices to Avoid	Large, long-lived predator.
Shark	0.979	Choices to Avoid	Top predator, bioaccumulation.
King Mackerel	0.730	Choices to Avoid	Larger individuals, top of food chain.
Bigeye Tuna	0.689	Choices to Avoid	High on the food chain, long life.
Orange Roughy	0.571	Choices to Avoid	Very long lifespan, slow maturation.
Marlin	0.485	Choices to Avoid	Large predator, accumulates mercury.
Canned Albacore Tuna	0.350	Good Choice (limited)	Higher mercury than light tuna.
Canned Light Tuna	0.126	Best Choice (2-3 servings/week)	Smaller species, lower on food chain.
Cod	0.111	Best Choice (2-3 servings/week)	Lower on the food chain.
Salmon	0.022	Best Choice (2-3 servings/week)	Lower on the food chain, shorter life.
Shrimp	0.009	Best Choice (2-3 servings/week)	Very low on food chain.

Safer Seafood Choices: Focus on Low-Mercury Fish

Choosing low-mercury options allows you to enjoy seafood benefits with less risk. These are typically smaller, shorter-lived species lower on the food chain.

Best Choices (2-3 servings per week):

• Salmon
• Shrimp
• Sardines
• Canned light tuna
• Catfish
• Anchovies
• Tilapia
• Pollock
• Scallops

Good Choices (1 serving per week):

• Halibut
• Snapper
• Mahi Mahi
• Canned albacore tuna (limit 4 oz/week for sensitive populations)

These choices provide nutritional benefits like omega-3s with reduced mercury risk.

How to Mitigate Your Mercury Risk

Managing your seafood intake is key. Mercury is in the muscle tissue, so cooking or removing skin doesn't help.

• Vary your fish choices from the 'Best' and 'Good' lists.
• Control portion sizes, especially for sensitive groups.
• Check local advisories for recreationally caught fish.
• Consider that larger, older fish generally have more mercury.

Conclusion

Identifying which sea fish has the most mercury, like the Gulf of Mexico tilefish, helps consumers make safer dietary choices. Avoiding high-mercury predators and opting for low-mercury fish such as salmon and sardines allows you to enjoy the health benefits of seafood while minimizing methylmercury exposure. Informed choices are vital for a balanced diet.

Further Reading

• For official guidelines on safe fish consumption, consult the FDA and EPA's advice: What You Need to Know About Mercury in Fish and Shellfish

Frequently Asked Questions

Which sea fish has the most mercury?

Tilefish from the Gulf of Mexico contains the highest average levels of mercury among sea fish, though other large predators like swordfish and shark also have very high concentrations.

Why do some fish contain more mercury than others?

Larger, long-lived predatory fish consume many smaller fish that contain trace amounts of mercury. Because mercury accumulates in their tissue and is not easily excreted, it builds up over their lifespan, a process called biomagnification.

Which fish should I avoid due to high mercury levels?

The FDA recommends avoiding fish with the highest mercury levels, including shark, swordfish, king mackerel, and tilefish from the Gulf of Mexico.

What are some low-mercury fish options?

Safe, low-mercury fish options include salmon, shrimp, sardines, canned light tuna, catfish, anchovies, and tilapia.

Is canned tuna high in mercury?

It depends on the type. Canned light tuna (typically skipjack) is relatively low in mercury and is considered a 'Best Choice,' while canned albacore ('white') tuna has higher levels and should be eaten less frequently.

Does cooking fish reduce its mercury content?

No, cooking methods do not reduce the mercury content of fish. The mercury is stored in the muscle tissue, not on the surface, so it cannot be cooked off.

Who should be most concerned about mercury in fish?

Pregnant women, women trying to conceive, nursing mothers, and young children are most vulnerable to the neurotoxic effects of methylmercury and should be particularly cautious about limiting high-mercury fish.