Which Fish Has the Least Mercury in It? Your Comprehensive Guide to Safer Seafood

The FDA and EPA advise that certain populations, including pregnant women and young children, limit their consumption of specific fish due to mercury contamination. Knowing which fish has the least mercury in it is crucial for making informed, health-conscious decisions, allowing you to enjoy the nutritional benefits of seafood with minimal risk.

Quick Summary

Smaller, shorter-lived fish and shellfish typically contain lower levels of mercury. This includes nutrient-dense choices like salmon, sardines, and shrimp, while larger, predatory fish like swordfish have the highest concentrations. Making informed choices helps reduce your mercury exposure while still enjoying the health benefits of seafood.

Key Points

• Sardines and Salmon are Safest: Smaller fish like sardines, anchovies, salmon, and shellfish have the lowest mercury levels, making them excellent choices for regular consumption.

• Avoid Large Predators: Bigger, longer-lived predatory fish such as shark, swordfish, and king mackerel accumulate the most mercury and should be avoided or severely limited.

• Canned Tuna Matters: Opt for canned light tuna (skipjack) over canned albacore (white) tuna, as it contains significantly less mercury.

• At-Risk Groups Need Caution: Pregnant or breastfeeding women, as well as young children, are more vulnerable to mercury's effects and should strictly follow consumption guidelines.

• Variety is Key: To minimize risk and maximize nutrient intake, eat a variety of different low-mercury fish and shellfish throughout the week.

• Farmed vs. Wild: Some research suggests farmed fish, like certain salmon and catfish, may have lower mercury levels than their wild-caught counterparts due to controlled environments.

Understanding Mercury in Fish

Mercury is a naturally occurring heavy metal that finds its way into waterways from both natural sources and human activities, such as coal-fired power plants. In water, bacteria convert this element into methylmercury, a highly toxic organic compound that fish absorb. As larger predatory fish consume smaller fish, the concentration of methylmercury bioaccumulates up the food chain, meaning the largest, longest-lived fish tend to have the highest levels. For humans, prolonged exposure to high levels of methylmercury can cause neurological and developmental problems. However, the nutritional benefits of eating fish, rich in omega-3 fatty acids, protein, and other essential nutrients, are substantial and can be safely enjoyed by choosing lower-mercury options.

The Safest Choices: Low-Mercury Fish and Shellfish

When aiming to reduce mercury intake, focusing on smaller species and shellfish is the best strategy. The FDA and EPA have compiled extensive lists of seafood classified by mercury content, making it easier for consumers to choose wisely.

Best Choices (Lowest Mercury):

• Anchovies: Tiny, oily fish with virtually no mercury and high omega-3 content.
• Atlantic Mackerel: Smaller mackerel species are a good choice; avoid king mackerel.
• Catfish: Farmed catfish is a very low-mercury option.
• Clams, Oysters, Scallops: Most shellfish are among the lowest in mercury.
• Cod: A mild, white fish that is widely available and low in mercury.
• Haddock: Similar to cod, with a mild flavor and low mercury levels.
• Herring: A small, oily fish rich in omega-3s and low in mercury.
• Pollock: A commonly used fish in fish sticks and fast food, with low mercury content.
• Salmon: Both wild and farm-raised salmon are excellent low-mercury choices and are packed with healthy fats.
• Sardines: A nutritional powerhouse, sardines are small, oily, and very low in mercury.
• Shrimp: A very popular shellfish with some of the lowest mercury concentrations.
• Squid (Calamari): A cephalopod with very low mercury levels.
• Tilapia: This farm-raised fish is a reliably low-mercury option.
• Trout (Freshwater): Another great low-mercury choice, especially farm-raised.
• Tuna (Canned Light): Specifically, canned light tuna, typically made from skipjack, has much lower mercury than albacore.

Moderate and High-Mercury Fish to Watch For

While a balanced diet includes variety, it's wise to limit or avoid fish that fall into the higher-mercury categories. This is particularly important for pregnant women, breastfeeding mothers, and young children, who should limit their intake of "Good Choices" fish and strictly avoid those on the "Choices to Avoid" list.

Good Choices (Moderate Mercury):

• Albacore (white) tuna (canned and fresh/frozen)
• Grouper
• Halibut
• Mahi-mahi
• Yellowfin tuna
• Atlantic Ocean tilefish

Choices to Avoid (Highest Mercury):

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

Mercury Levels in Common Fish

Fish Type	Mercury Level (ppm, average)	Primary Reason for Level	Recommended Consumption	Source
Sardines	0.013	Small size, low on food chain	Best Choice (2-3 times/week)
Salmon	0.022	Short lifespan, not predatory	Best Choice (2-3 times/week)
Shrimp	0.009	Small invertebrate, low on food chain	Best Choice (2-3 times/week)
Canned Light Tuna	~0.04	Typically skipjack, smaller species	Best Choice (2-3 times/week)
Cod	0.111	Moderate size, varied diet	Best Choice (2-3 times/week)
Yellowfin Tuna	~0.35	Larger, more predatory	Good Choice (Limit to 1 meal/week)
Albacore Tuna	~0.35	Larger, more predatory than skipjack	Good Choice (Limit to 1 meal/week)
Swordfish	0.995	Large predator, long lifespan	Choice to Avoid (Limit to 1 meal/fortnight)
King Mackerel	0.73	Large predator, long lifespan	Choice to Avoid (Limit)

Factors Influencing Mercury Contamination

Several factors contribute to the level of mercury in a fish, providing additional insight into making safer choices:

• Size and Age: Larger, older fish have had more time to accumulate mercury from their environment and prey.
• Food Chain Position: Fish at the top of the food chain, such as sharks and swordfish, consume many smaller fish, leading to higher mercury accumulation.
• Habitat and Environment: The specific water body can play a role. Local advisories exist for specific lakes, rivers, or coastal areas where mercury levels may be higher than average due to localized pollution.
• Wild vs. Farmed: Research suggests that farmed fish may contain less mercury than their wild-caught counterparts, as their feed and environment are more controlled. For example, studies found that mercury levels were lower in farmed fish compared to wild-caught fish, though both were within safe limits.

How to Reduce Your Exposure

In addition to choosing lower-mercury fish, you can take other steps to minimize your intake:

• Diversify Your Choices: Instead of eating the same type of fish all the time, vary your selections from the “Best Choices” list. This helps balance your exposure and ensures you get a wider range of nutrients.
• Moderate Intake of Higher-Mercury Fish: If you do eat fish from the “Good Choices” list, follow the recommended serving limits. For most adults, this means no more than one average meal per week.
• Be Mindful of Local Advisories: If you consume fish caught by friends or family from local waterways, check for advisories from your local health or environmental department. Local conditions can sometimes lead to unexpectedly high mercury levels.

Conclusion: Making Informed Decisions

For anyone looking to maintain a healthy diet, particularly those in vulnerable populations, understanding which fish has the least mercury in it is a vital part of seafood consumption. By prioritizing smaller, shorter-lived species like salmon, sardines, and shellfish, and moderating or avoiding larger predatory fish, you can reap the numerous benefits of seafood, including essential omega-3s, while effectively managing your exposure to mercury. Always refer to the latest guidelines from health organizations like the FDA and EPA to ensure your choices are based on the most up-to-date scientific recommendations. For more information on seafood consumption guidelines, refer to the official FDA advice(https://www.fda.gov/food/consumers/advice-about-eating-fish).

Frequently Asked Questions

What are some of the lowest mercury fish I can eat regularly?

Some of the lowest mercury fish and shellfish options include sardines, salmon, cod, shrimp, anchovies, tilapia, and freshwater trout.

Why do larger fish tend to have higher mercury levels?

Larger, predatory fish are at the top of the aquatic food chain. They consume many smaller fish, and over their longer lifespan, the mercury they absorb bioaccumulates in their bodies to higher concentrations.

Is canned tuna a safe choice, or does it have a lot of mercury?

It depends on the type. Canned 'light' or skipjack tuna is considered a 'Best Choice' with low mercury levels. Canned albacore ('white') tuna has higher levels and should be limited.

Is it better to eat farmed fish or wild-caught fish to reduce mercury intake?

Studies suggest that farmed fish may have lower mercury levels than wild-caught fish, likely due to a more controlled environment and diet. For example, farmed salmon typically contains less mercury than wild salmon.

How often can pregnant women and young children safely eat fish?

The FDA and EPA advise that pregnant and breastfeeding women, and young children, eat 2 to 3 servings per week of 'Best Choices' fish. They should avoid 'Choices to Avoid' fish entirely.

Does cooking fish change its mercury content?

No, cooking fish does not reduce its mercury content. The methylmercury is bound to the fish's protein and is not released through standard cooking methods.

What are the health risks of eating high-mercury fish?

Excessive mercury exposure can lead to neurological issues, such as tremors, memory problems, and loss of coordination. It is especially harmful to the developing nervous system of an unborn baby or young child.