Which Has Less Mercury: Mackerel or Tuna? A Complete Breakdown

November 15, 2025 •

4 min read

With mercury levels varying significantly even within the same species, the question of whether mackerel or tuna has less mercury depends heavily on the specific type of fish you're choosing. In general, smaller, short-lived fish contain less mercury than larger, predatory ones due to bioaccumulation up the food chain.

Quick Summary

Comparing mackerel and tuna for mercury requires distinguishing between species. Generally, smaller mackerel species and light canned tuna have lower mercury levels than larger, long-lived tuna. Your choice should align with FDA/EPA guidelines, especially for vulnerable populations.

Key Points

Species Matters: Mackerel is generally lower in mercury than tuna, but the specific species of each fish is the determining factor.
Choose Low-Mercury Types: Opt for Atlantic mackerel or canned light tuna (skipjack), which are categorized as 'Best Choices' by the FDA/EPA.
Limit High-Mercury Fish: Avoid king mackerel and bigeye tuna, which are among the highest in mercury due to their size and diet.
Bioaccumulation is Key: Larger, older fish higher up the food chain, such as bigeye tuna, accumulate more mercury than smaller fish like Atlantic mackerel.
Cooking Does Not Remove Mercury: Since mercury accumulates in the muscle tissue, cooking methods cannot eliminate it.
Vulnerable Populations Need Caution: Pregnant women, nursing mothers, and young children should adhere strictly to consumption limits for moderate-mercury fish and avoid high-mercury options entirely.

The Simple Answer: It Depends on the Species

Determining whether mackerel or tuna has less mercury is not a straightforward 'either-or' question; the answer is highly dependent on the specific species and its size. A fundamental principle of mercury accumulation in seafood is bioaccumulation, the process by which a substance like mercury accumulates in an organism. This means larger, older, and more predatory fish tend to have higher concentrations of mercury because they eat other, smaller fish that have already accumulated some mercury. Therefore, smaller species of fish, which are lower on the food chain, typically contain less mercury. As we will see, this principle is crucial when comparing the two fish families.

Mercury Content: Mackerel vs. Tuna Breakdown

The mercury levels in mackerel and tuna vary widely across their different species and preparation methods.

Mackerel Species and Mercury

While the mackerel family includes some of the highest-mercury fish, it also offers some of the lowest.

Atlantic Mackerel: Considered a "Best Choice" by the FDA and EPA for its very low mercury content. A small, fast-growing fish, it is a safe, omega-3 rich option for regular consumption.
Chub Mackerel (Pacific Mackerel): Also a low-mercury option and listed as a "Best Choice".
King Mackerel: This species is a major exception and should be avoided, especially by pregnant women and young children, due to its high mercury levels. Its larger size and longer lifespan allow for significant mercury accumulation.
Spanish Mackerel: Categorized as a "Good Choice" by the FDA, meaning it has moderate mercury levels and consumption should be limited.

Tuna Species and Mercury

Tuna species also show a broad range of mercury levels, from low to high.

Canned Light Tuna (Skipjack): A "Best Choice" for its low mercury content, making it safe to eat up to two or three servings per week. Most canned "light" tuna is made from smaller skipjack tuna.
Albacore Tuna: Often called "white" tuna, albacore has higher mercury levels than canned light tuna. The FDA lists it as a "Good Choice" but recommends limiting consumption, especially for sensitive populations.
Bigeye Tuna: This large species has some of the highest mercury levels among tuna and is classified as a "Choice to Avoid" by the FDA due to its potential health risks. It is typically found fresh or frozen rather than in cans.
Yellowfin Tuna: Categorized as a "Good Choice," yellowfin has moderate mercury levels, placing it between canned light and albacore tuna.

Nutritional Comparison Beyond Mercury

While mercury is a key concern, it's also worth noting the other nutritional aspects of these fish.

Omega-3 Fatty Acids: Mackerel is an oily fish and generally contains significantly higher levels of heart-healthy omega-3 fatty acids than tuna. A 3.5-ounce serving of mackerel can have over 4,000 mg of omega-3s, while tuna offers a more modest amount.
Protein: Both are excellent sources of protein. However, tuna tends to be leaner, with a higher protein-to-fat ratio than mackerel.
Vitamins and Minerals: Both fish offer a range of essential nutrients, including vitamin D and B12. Mackerel is particularly high in vitamin B12, while tuna offers more selenium and phosphorus.

Safe Fish Selection Tips

When choosing seafood, a few practical tips can help you minimize mercury exposure:

Favor Smaller Species: The golden rule is to choose smaller, younger fish that are lower on the food chain, as they accumulate less mercury.
Diversify Your Choices: Instead of eating the same type of fish repeatedly, vary your seafood consumption to reduce exposure from a single source. The FDA/EPA recommends eating a variety of fish from the "Best Choices" list.
Consult Advisories: Pay attention to local and national fish consumption advisories, which provide guidance based on the latest data. You can find official guidance on the FDA/EPA advice about eating fish website.

Mackerel vs. Tuna: Mercury and Nutrients Comparison Table


Feature	Atlantic Mackerel (Best Choice)	Canned Light Tuna (Best Choice)	Albacore/Yellowfin Tuna (Good Choice)	King Mackerel/Bigeye Tuna (Avoid)
Mercury Level	Very Low	Low	Moderate	Very High
FDA/EPA Rating	Best Choice	Best Choice	Good Choice	Choice to Avoid
Omega-3s	Very High	Moderate	Moderate	High
Protein	High	High	Very High	High
Typical Size	Small	Small to medium (Skipjack)	Medium to large	Very large
Consumption Limit	2-3 servings/week+	2-3 servings/week+	1 serving/week (sensitive pop.)	Avoid

Conclusion: Making the Safest Choice

For individuals seeking the lowest mercury levels, the choice between mackerel and tuna depends entirely on the specific variety. Smaller mackerel species, such as Atlantic or Chub mackerel, are consistently rated as low-mercury options and are nutritionally dense. Similarly, canned light tuna, typically sourced from skipjack tuna, offers a low-mercury, convenient alternative. However, larger, long-lived tuna species like bigeye and king mackerel should be limited or avoided due to their high mercury content, especially by at-risk groups like pregnant women, nursing mothers, and young children. By focusing on smaller species and varying your fish intake, you can confidently enjoy the significant health benefits of seafood while minimizing mercury exposure.

Frequently Asked Questions

No, not all mackerel is low in mercury. While smaller species like Atlantic and Chub mackerel are very low in mercury, the larger King mackerel has a high concentration and should be limited or avoided.

Canned light tuna, which is typically made from smaller skipjack tuna, has significantly less mercury than canned white (albacore) tuna. The FDA lists it as a 'Best Choice'.

For pregnant women, smaller species are safer. Atlantic mackerel and canned light tuna are 'Best Choices' for low mercury. High-mercury fish like king mackerel and bigeye tuna should be avoided.

Larger, older fish that are higher on the food chain tend to have higher levels of mercury. This is due to a process called bioaccumulation, where mercury builds up in their systems over time by consuming other fish.

No, cooking does not remove mercury. Mercury is found in the muscle tissue of the fish, so methods like baking, grilling, or frying will not reduce the mercury content.

Yes, mackerel is an oily fish and is an excellent source of omega-3 fatty acids, with higher concentrations than most tuna. It also offers a variety of vitamins and minerals.

For most people, including pregnant and breastfeeding women, the FDA advises eating 2 to 3 servings (8 to 12 ounces) of low-mercury fish, such as canned light tuna, per week.