Which is the safest seafood to eat?

December 15, 2025 •

4 min read

Methylmercury, a contaminant found in many aquatic organisms, can become highly concentrated in large predatory fish, a process known as biomagnification. For consumers, this highlights the importance of understanding which seafood options carry the lowest risk while still providing valuable nutrients like omega-3 fatty acids.

Quick Summary

Identify seafood with low levels of mercury and other contaminants. This resource clarifies the risks associated with different species, outlines how to choose safer options, and details proper preparation techniques.

Key Points

Prioritize smaller fish and shellfish: Focus on species lower on the food chain, such as sardines, anchovies, shrimp, and scallops, to minimize mercury and other contaminant exposure.
Choose wisely among popular options: Opt for canned light tuna over bigeye tuna, and wild-caught salmon over potentially less regulated farmed varieties.
Avoid large predatory fish: Species like shark, swordfish, and king mackerel accumulate high levels of mercury and should be limited or avoided entirely.
Cook thoroughly: Properly cooking seafood, especially shellfish, is critical for killing bacterial and viral pathogens like Vibrio and Norovirus.
Trim fat: To reduce intake of fat-soluble contaminants like PCBs, remove the skin and fatty portions of fish before cooking.
Consult reputable guides: Use resources like the Monterey Bay Aquarium Seafood Watch program to find current recommendations on sustainable and safe seafood.

Understanding Seafood Contamination

When evaluating the safety of seafood, consumers must consider potential contaminants that can accumulate in fish and shellfish over time. The two primary concerns are:

Mercury: Released into the atmosphere by both natural and industrial sources, mercury can be converted to methylmercury in aquatic environments. It is then absorbed by small organisms and accumulates in the muscle tissue of fish through the food chain, with larger, older predatory fish having the highest concentrations due to a process called biomagnification.
PCBs (Polychlorinated Biphenyls): These man-made industrial chemicals, though banned in the U.S. since 1979, persist in the environment. PCBs are highly fat-soluble and accumulate in the fatty tissues of aquatic organisms. They biomagnify up the food chain, with higher levels found in fatty fish, especially older ones.

Both mercury and PCBs can pose significant health risks with long-term exposure, affecting the nervous system, immune system, and development, particularly in children and pregnant women.

Safest Choices: The 'Best' and 'Good' Options

Making safer seafood choices involves prioritizing species lower on the food chain and considering their source. The Monterey Bay Aquarium Seafood Watch program offers excellent, scientifically-backed recommendations to guide consumers toward environmentally responsible and healthier options.

Fish and Shellfish with Lowest Contaminant Levels

Sardines and Anchovies: These small, oily fish are low in mercury and high in omega-3s. Because of their short lifespan and diet, they accumulate very few contaminants.
Shrimp and other Shellfish: Most crustaceans and mollusks, such as shrimp, clams, oysters, and scallops, are very low in mercury and offer a safe protein source. Cooking thoroughly is essential to minimize the risk of bacterial or viral pathogens.
Salmon: Wild-caught Alaska salmon and canned salmon are considered low in mercury. Farmed salmon can also be a good option if sourced from well-managed, eco-friendly farms, such as those certified by the Aquaculture Stewardship Council (ASC).
Trout: Farmed rainbow trout, particularly from the U.S. or in indoor recirculating tanks, is a sustainable and low-mercury choice.
Tilapia: Farmed tilapia is a low-mercury, affordable fish option.
Mackerel: Atlantic mackerel and Pacific chub mackerel are good choices with low mercury levels, in contrast to the higher-mercury King mackerel.

Seafood to Limit or Avoid

Some species consistently appear on lists of high-mercury fish due to their size, age, and position at the top of the marine food chain.

High-Mercury Fish

Shark: A top predator with some of the highest recorded mercury levels.
Swordfish: Also a large predator, listed as high in mercury by the FDA.
King Mackerel: Distinct from its smaller Atlantic and Pacific cousins, this large mackerel species has high mercury content.
Tilefish (Gulf of Mexico): This species, particularly from the Gulf, contains very high mercury levels and should be avoided.
Bigeye Tuna: This specific tuna variety has significantly higher mercury levels than canned light tuna.
Orange Roughy: A long-lived species that accumulates high levels of mercury.

Comparison of Seafood Contaminant Risks

Here is a table comparing some common seafood options based on their typical mercury levels and other potential risks.


Seafood Type	Typical Mercury Level	PCB / Fat Content	Pathogen Risk (If raw)
Sardines	Very Low	High (Healthy Omega-3 Fat)	Low
Wild Salmon	Low	High (Healthy Omega-3 Fat)	Low
Shrimp	Very Low	Very Low	Yes (Vibrio)
Oysters	Very Low	Very Low	Yes (Vibrio, Norovirus, Hepatitis A)
Canned Light Tuna	Low	Low	Very Low
Crab	Low	Low	Yes (Vibrio, etc.)
King Mackerel	Very High	High	Low
Swordfish	Very High	Medium	Low
Shark	Very High	High	Low
Bigeye Tuna	High	High	Low

Sustainable Sourcing and Certifications

In addition to contaminant levels, the sourcing of your seafood is critical for both environmental health and human safety. Organizations provide resources to help consumers make informed decisions.

Monterey Bay Aquarium Seafood Watch: This program provides detailed recommendations for wild-caught and farmed seafood based on scientific assessments of sustainability. Their ratings use a simple color-coding system: green for 'Best Choice', yellow for 'Good Alternative', and red for 'Avoid'.
Certifications: Look for seafood carrying labels from recognized third-party certifiers. The Marine Stewardship Council (MSC) certifies sustainable wild fisheries, while the Aquaculture Stewardship Council (ASC) focuses on responsible farming practices.
Proper Preparation: While cooking doesn't eliminate mercury, it is crucial for killing harmful bacteria and viruses, especially in shellfish. PCBs and dioxins, which concentrate in fat, can be reduced by trimming the skin and fatty portions before cooking. Baking, broiling, or grilling on a rack allows fat to drip away, further reducing intake.

Conclusion

While potential risks like mercury, PCBs, and pathogens exist in some seafood, the benefits of consuming low-contaminant fish rich in omega-3s are well-established. By opting for smaller, shorter-lived species like sardines, salmon, and most shellfish, you can significantly reduce your exposure to harmful substances. Always cook seafood thoroughly, particularly shellfish, and use resources like the Monterey Bay Aquarium's Seafood Watch guide to make informed choices that are both healthy for you and the planet. For personalized advice, particularly for vulnerable populations like pregnant women and young children, always consult your doctor or health authority guidelines, which often provide specific recommendations for fish consumption.

An excellent resource for up-to-date seafood ratings can be found here: Seafood Watch.

Frequently Asked Questions

Canned light tuna is generally a safe option with low mercury levels because it's made from smaller, younger skipjack or yellowfin tuna. Canned white (albacore) tuna, however, has higher mercury content and should be consumed less frequently.

The safest seafood for pregnant women includes options that are both low in mercury and high in beneficial omega-3s, such as salmon, sardines, and trout. Health authorities provide specific weekly consumption limits for pregnant women to ensure safety.

No, cooking does not reduce the mercury content in fish. Mercury is bound to the muscle tissue, so preparation methods like baking or frying will not remove it. The best way to reduce mercury intake is to choose species known to have low levels.

You cannot visually detect PCBs in seafood. These chemicals accumulate in the fat and are tasteless. The best way to minimize exposure is to choose smaller, less fatty fish and to trim away the skin and fat before cooking.

Eating raw or undercooked shellfish, such as oysters, mussels, or clams, carries a risk of exposure to bacteria (like Vibrio and Salmonella) and viruses (like Norovirus). Sourcing from regulated waters is important, but thorough cooking is the most reliable way to ensure safety.

It depends on the species and farming practices. Some U.S.-farmed fish, like rainbow trout, are excellent choices. Conversely, some intensive, open-net pen farming can raise environmental and contamination concerns. Wild-caught options are not uniformly safer; larger wild predators have high mercury levels.

Harmful algal blooms (HABs), also known as 'red tides,' can produce marine toxins that contaminate filter-feeding shellfish like mussels and clams. These toxins, which are not destroyed by cooking, can cause severe illness, including amnesic or paralytic shellfish poisoning.