What has more mercury, tuna or tilapia?

November 17, 2025 •

3 min read

According to data from the FDA, tuna contains significantly more mercury than tilapia. This critical difference is primarily due to the process of bioaccumulation, where mercury levels increase as it moves up the food chain, positioning predatory fish like tuna as a higher-mercury option compared to lower-chain feeders like tilapia.

Quick Summary

Tuna accumulates higher mercury levels than tilapia due to its predatory nature and higher position in the food chain. Mercury content in tuna also varies greatly by species, with larger types containing the most, making species choice important.

Key Points

Tuna has significantly more mercury than tilapia: Due to its predatory nature and higher position on the food chain, tuna accumulates higher levels of mercury through bioaccumulation.
Tilapia is a low-mercury fish: As a low-trophic-level, often farmed fish with an herbivorous diet, tilapia consistently contains very low levels of mercury.
Mercury levels vary greatly among different types of tuna: Canned light or skipjack tuna contains the lowest mercury among tuna varieties, while fresh or frozen albacore and bigeye tuna have the highest concentrations.
Vulnerable populations should limit or avoid high-mercury fish: Pregnant women, nursing mothers, and young children are particularly susceptible to the effects of mercury and should follow specific consumption guidelines.
Informed choices can reduce mercury intake: Opting for lower-mercury species like tilapia, salmon, or shrimp, and choosing canned light tuna over albacore when eating tuna, can help manage overall mercury consumption.
The larger the fish, the higher the mercury concentration: As a general rule of thumb, bigger, older predatory fish like large tuna will have higher levels of accumulated mercury in their tissues.

The Science of Mercury Bioaccumulation

Mercury exists naturally in the environment and as a result of industrial pollution. When it enters waterways, bacteria convert it into a highly toxic form called methylmercury, which is then absorbed by aquatic life. This methylmercury builds up in the tissues of organisms faster than it can be excreted. A key principle of toxicology is that this concentration intensifies at each level of the food chain, a process known as biomagnification. Small organisms consume mercury-contaminated plankton, and then larger fish prey on those smaller fish, accumulating the mercury they contain.

How Bioaccumulation Impacts Tuna and Tilapia

Tuna's Predatory Habits: As a top predator in the marine food chain, tuna consumes many smaller, mercury-laden fish throughout its lifespan. Because mercury accumulates over time, larger and older tuna species, like bigeye, will have the highest concentrations. This is why all types of tuna, even the canned varieties, contain more mercury than tilapia.
Tilapia's Lower Trophic Level: Tilapia, by contrast, is a low-mercury fish for several reasons. It is typically farmed and feeds on a primarily herbivorous diet, which is low in mercury. This places it at a much lower trophic level, meaning it is less exposed to mercury-contaminated prey. The result is a consistently low mercury content, though local pollution in wild tilapia habitats can increase levels.

Comparison of Mercury Content: Tuna vs. Tilapia

The amount of mercury in tuna is not uniform; it varies significantly by species and size. Smaller, younger species like skipjack have the lowest levels of tuna mercury, while larger species like bigeye have the highest. Tilapia consistently ranks among the lowest mercury seafood options available. The following table, based on FDA data, highlights the stark differences.

Mercury Levels: Tuna vs. Tilapia (Mean ppm)


Species	Mercury Concentration (Mean ppm)
Tilapia	0.013
Tuna (Canned, Light)	0.126
Tuna (Canned, Albacore)	0.350
Tuna (Fresh/Frozen, Yellowfin)	0.354
Tuna (Fresh/Frozen, Bigeye)	0.689

Health Recommendations and Consumption Guidelines

While all fish contains some trace amount of mercury, health organizations provide guidelines to help consumers enjoy the benefits of seafood while minimizing risk.

Who Needs to Be Careful?

Vulnerable Populations: Pregnant women, nursing mothers, and young children are most susceptible to the neurological effects of mercury and should be the most careful. The NHS, for example, advises pregnant women to limit tuna intake and avoid high-mercury fish like shark altogether.
Regular Fish Eaters: For the general adult population, moderation is key. Regularly consuming high-mercury fish could lead to a buildup over time. The FDA recommends eating 2–3 servings per week of low-mercury fish.

Choosing Your Fish Wisely

To minimize your mercury exposure, you can take a few simple steps:

Select Lower-Mercury Varieties: Choose lower-mercury fish and shellfish like tilapia, salmon, shrimp, and cod more frequently.
Pick the Right Tuna: When eating tuna, opt for canned light or skipjack varieties instead of albacore or bigeye. Canned light tuna has significantly lower mercury levels than albacore.
Check Local Advisories: If you consume wild-caught fish, check with local authorities for any water-specific contamination advisories.

For authoritative information, consider consulting the FDA's Mercury Levels in Commercial Fish and Shellfish data.

Conclusion: Making Informed Seafood Choices

When comparing tuna and tilapia, the answer is clear: tuna has substantially more mercury, especially the larger, fresh varieties. Tilapia is a much lower-mercury choice, making it a safer option for frequent consumption and for vulnerable populations. By understanding the differences in mercury accumulation between these fish, consumers can make informed decisions to balance the health benefits of seafood with managing mercury intake. Always refer to current health guidelines for the most accurate and up-to-date recommendations.

Frequently Asked Questions

Yes, it is safe to eat tuna in moderation. The amount you can safely consume depends on the type of tuna (canned light is lower mercury than albacore) and your individual health, especially if you are in a vulnerable group like pregnant women or young children.

Yes, tilapia is a lean source of protein and a very low-mercury fish, making it a healthy option for most people. Concerns are more commonly related to farming practices or local pollution, not mercury content.

Larger, predatory fish like tuna accumulate mercury through a process called bioaccumulation. They eat many smaller fish throughout their longer lives, and since mercury is not easily flushed from their systems, it builds up over time.

Canned light or skipjack tuna is the safest option in terms of mercury content. These species are smaller and have a shorter lifespan, resulting in less mercury accumulation compared to albacore or bigeye tuna.

For most healthy adults, the FDA recommends consuming 8 to 12 ounces of low-mercury fish per week. For tuna specifically, this translates to about 3 servings of canned light tuna or 1 serving of albacore tuna per week.

Generally, yes, farmed fish like tilapia often have lower mercury levels than many wild-caught species, especially large predators. This is because their diet is controlled and typically has lower mercury content than a natural aquatic food chain.

Excellent low-mercury alternatives include tilapia, salmon, cod, shrimp, sardines, and catfish. These options provide protein and other nutrients with a lower risk of mercury exposure.