Which fish has no mercury in it? A Guide to the Safest Seafood Choices

December 24, 2025 •

3 min read

While it is impossible to find a fish with absolutely no mercury due to global environmental contamination, numerous species contain such negligible amounts that they are considered among the safest to eat. The key to minimizing exposure is understanding which fish has no mercury in it, or at least the lowest levels, and making informed choices based on factors like the fish's size and diet.

Quick Summary

This guide examines the reality of mercury in seafood, explaining why no fish is entirely free of it, but offers a definitive list of species with the lowest levels. It details the factors influencing mercury accumulation and provides practical advice on selecting the safest, healthiest fish options for regular consumption.

Key Points

No Fish is Mercury-Free: Due to environmental bioaccumulation, all fish contain some level of mercury, but levels vary significantly by species.
Best Low-Mercury Choices: Small, short-lived fish and shellfish are your safest bets, including sardines, salmon, shrimp, and tilapia.
Avoid High-Mercury Predators: Larger, long-lived predatory fish like shark, swordfish, and king mackerel accumulate the highest levels of mercury and should be limited or avoided.
Prioritize Low-Trophic Species: Fish lower on the food chain, such as those that eat plankton, have the least amount of mercury.
Diversify Your Diet: Consuming a variety of seafood helps to mitigate mercury exposure from any single source.

Understanding Mercury in Seafood: The Scientific Reality

Mercury is a naturally occurring element, but industrial pollution has increased its presence in the environment. In aquatic systems, bacteria convert inorganic mercury into a more toxic form, methylmercury, which is then absorbed by fish and other marine life. This process is known as bioaccumulation, and it is the primary reason why finding a fish with truly no mercury in it is impossible. Mercury levels increase as you move up the food chain, a process called biomagnification. This means larger, predatory fish that consume smaller, mercury-containing fish will have significantly higher concentrations of the toxin in their systems. Conversely, smaller, shorter-lived fish and shellfish that feed on plankton generally have the lowest levels of mercury.

The Low-Mercury Champions: The Safest Seafood Choices

While a zero-mercury fish is a myth, many species have levels so low that they are considered safe for regular consumption by health authorities like the FDA and EPA. These include smaller, non-predatory fish and certain types of shellfish.

List of Best Choices for Low-Mercury Seafood

Sardines: These small, oily fish are consistently ranked among the safest seafood choices. Their short lifespan and plankton-based diet result in very low mercury levels.
Anchovies: Similar to sardines, anchovies are tiny, short-lived, and near the bottom of the marine food chain. They are an excellent low-mercury option.
Salmon: Both wild-caught Alaskan and farmed salmon are generally low in mercury. They are also packed with beneficial omega-3 fatty acids, making them a top choice.
Shrimp: A popular shellfish, shrimp consistently shows very low mercury levels, making it a safe choice for frequent meals.
Tilapia: This freshwater fish is known for its mild flavor and low mercury content, making it a staple for many families.
Catfish: Often farmed, catfish has a very low mercury content and is a versatile, protein-rich option.
Pollock: Commonly used in fish sticks and fast-food sandwiches, pollock is a mild white fish with low mercury levels.
Cod: A flaky white fish, cod is also a low-mercury choice, particularly when sourced from the Atlantic.
Crab: Most crab species, including domestic U.S. varieties, contain low levels of mercury.
Squid (Calamari): This cephalopod is a low-mercury choice and a good source of protein.

How to Minimize Mercury Intake

Beyond choosing species with inherently lower mercury, there are other strategies to reduce your exposure:

Prioritize smaller fish: As a general rule, the smaller the fish, the lower the mercury. This is because it has had less time to accumulate the metal.
Diversify your seafood: Don't rely on just one type of fish. By rotating your seafood choices, you can balance your nutrient intake and minimize potential exposure from any single source.
Check local advisories: If you consume locally caught fish, check advisories from your local environmental or health agency, as regional pollution levels can affect mercury content.
Consider farmed vs. wild: Some studies suggest that certain farmed fish may have lower mercury levels than their wild-caught counterparts due to controlled feeding, though both types generally remain within safe limits for low-mercury species.

Comparison Table: High vs. Low Mercury Fish

This table provides a quick overview of common seafood choices and their general mercury classification, based on FDA guidelines.


Seafood Type	Mercury Level	Notes
Sardines	Best Choice (Lowest)	Small, short-lived plankton eaters.
Salmon	Best Choice (Lowest)	Often farmed or wild-caught Alaskan.
Cod (Alaskan)	Best Choice (Lowest)	Flaky white fish, mild flavor.
Shrimp	Best Choice (Lowest)	Common and versatile shellfish.
Tuna (Canned Light)	Best Choice (Lowest)	Made from smaller skipjack tuna.
Tuna (Canned Albacore)	Good Choice (Moderate)	From larger fish; has higher levels than light tuna.
Mahi Mahi	Good Choice (Moderate)	Predatory fish, but generally lower than top predators.
Swordfish	Avoid (Highest)	Large, top-level predator.
King Mackerel	Avoid (Highest)	Large, predatory fish.
Shark	Avoid (Highest)	Apex predator with high mercury content.

Conclusion

While the search for a fish with absolutely no mercury in it is futile, focusing on species with the lowest levels is a practical and health-conscious approach. Small, short-lived fish and shellfish like sardines, salmon, shrimp, and tilapia are consistently the safest choices, allowing you to reap the numerous health benefits of seafood—such as omega-3 fatty acids—without undue worry. By making informed selections and varying your diet, you can confidently enjoy a wide range of nutritious and delicious seafood options.

For more detailed information, the U.S. Food and Drug Administration (FDA) website provides a comprehensive resource on mercury levels and safe eating guidelines.

Frequently Asked Questions

No, it is not possible for any fish to be completely free of mercury. Due to global environmental pollution, all fish absorb some level of methylmercury from the water they live in. The key is to choose species with very low, negligible amounts.

Some of the fish with the lowest mercury levels include sardines, anchovies, salmon, shrimp, tilapia, pollock, and catfish. These species are smaller and lower on the food chain.

Mercury levels increase through a process called biomagnification. Larger, predatory fish eat smaller fish, absorbing their accumulated mercury. This means top predators like shark and swordfish have the highest concentrations, while smaller, plant-eating fish have the lowest.

The mercury level in canned tuna depends on the type. Canned 'light' tuna (often skipjack) is low in mercury and considered a 'best choice.' Canned 'albacore' or 'white' tuna comes from a larger species and has a moderate mercury level, so consumption should be more limited.

No, cooking does not reduce the mercury content of fish. The methylmercury is tightly bound to the fish's protein, so it remains in the meat whether it is cooked, baked, or eaten raw.

Methylmercury is a highly toxic organic form of mercury that is easily absorbed by the body. It is a neurotoxin that can cause harm to the nervous system, especially in unborn babies and young children, and can affect brain development.

For low-mercury fish, health experts like the FDA recommend eating two to three servings per week. Pregnant and breastfeeding women and young children should adhere to specific guidelines, often limiting intake to around two servings per week.