Does Wahoo Have a Lot of Mercury? A Guide to Consumption

December 22, 2025 •

3 min read

While many types of fish are an excellent source of lean protein and heart-healthy omega-3s, some, including wahoo, can contain elevated levels of mercury. The amount of mercury depends on factors like the fish's size, age, and diet, and potential health impacts are most significant for vulnerable groups.

Quick Summary

Wahoo, a large predatory fish, contains moderate to high levels of mercury, classifying it as a 'Good Choice' for consumption with weekly limits recommended by health authorities. Pregnant women, nursing mothers, and young children should exercise greater caution due to mercury's neurotoxic effects on developing nervous systems.

Key Points

Wahoo Contains Moderate-to-High Mercury: As a large, predatory fish, wahoo (ono) accumulates moderate-to-high levels of methylmercury.
Consumption Should Be Limited: For most adults, health authorities advise limiting wahoo consumption to about one serving per week to manage mercury exposure.
Vulnerable Groups Need Caution: Pregnant or breastfeeding women and young children should severely limit or avoid wahoo entirely due to mercury's risks to a developing nervous system.
Choose a Variety of Fish: To get the health benefits of seafood with less risk, opt for a wider variety of low-mercury fish like salmon, sardines, and tilapia.
Size Matters for Mercury Levels: Larger, older wahoo tend to have higher mercury concentrations, so choosing smaller, younger fish is a safer option.
Benefits Outweigh Risks for Most Adults: For those without health vulnerabilities, the nutritional benefits of fish, including omega-3 fatty acids, often outweigh the potential risk from moderate, mindful mercury intake.

Wahoo (Acanthocybium solandri), often known as 'ono' in Hawaii, is a swift, powerful oceanic fish prized for its firm texture and mild, sweet flavor. However, like other large predatory fish, it accumulates mercury, a neurotoxin that can pose health risks if consumed in high quantities over time. Understanding the factors influencing mercury levels and following expert consumption advice is key to enjoying this nutritious fish safely.

The Science of Mercury in Fish

Mercury is a naturally occurring element, but industrial pollution has increased its presence in the environment. In aquatic ecosystems, microorganisms convert this element into methylmercury, a highly toxic organic form that is then absorbed by small fish.

Bioaccumulation and Biomagnification

Bioaccumulation: As fish absorb methylmercury, it binds to proteins in their muscle tissue and accumulates over their lifespan.
Biomagnification: This process causes mercury concentrations to increase as you move up the food chain. Smaller fish with low mercury are eaten by larger fish, which are in turn eaten by even larger fish. Wahoo, being a top-level predator, sits high on this food chain, explaining its elevated mercury levels.

Factors Influencing Mercury in Wahoo

Age and Size: Older, larger wahoo generally have higher mercury levels than younger, smaller individuals, as they have had more time to accumulate the neurotoxin.
Diet: A wahoo's diet of smaller fish directly contributes to its mercury content.
Location: Mercury levels can vary depending on the specific ocean waters a fish inhabits, influenced by localized environmental factors.

Wahoo Mercury Levels in Perspective

Official health advisories provide context on where wahoo's mercury content stands compared to other common seafood choices. The U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) offer a helpful framework for consumption. While not as high in mercury as species like king mackerel or swordfish, wahoo is typically categorized as a 'Good Choice,' indicating that it can be enjoyed with weekly limits.

Comparison Table: Mercury Levels in Fish


Fish Species	Mercury Concentration (Average µg/g)	FDA/EPA Category	Consumption Advice	[Source]
Wahoo (Ono)	~0.50 (range: 0.021-3.4)	Good Choice	Eat 1 serving per week
Tuna, Canned Light	0.13	Best Choice	Eat 2-3 servings per week
Tuna, Fresh/Frozen Yellowfin	0.35	Good Choice	Eat 1 serving per week
Swordfish	1.00	Choices to Avoid	Do not eat for vulnerable populations
King Mackerel	0.73	Choices to Avoid	Do not eat for vulnerable populations
Salmon, Fresh/Frozen	0.02	Best Choice	Eat 2-3 servings per week

Note: Vulnerable populations include pregnant women, nursing mothers, and young children.

Balancing Risks and Benefits

Eating fish offers numerous health benefits, and for most adults, moderate consumption of wahoo is considered safe. Wahoo is a lean, protein-rich fish that provides omega-3 fatty acids, B vitamins, and minerals like potassium and selenium. Health advisories do not suggest forgoing fish entirely, but rather making informed choices based on mercury content.

Practical Recommendations

For the general adult population, eating one serving of wahoo per week is a common recommendation. However, vulnerable groups must be more cautious.

For vulnerable individuals (pregnant or breastfeeding women, young children):

Limit wahoo consumption: Some advisories suggest limiting 'ono' (wahoo) to no more than once every two weeks.
Vary your fish intake: Emphasize fish from the 'Best Choices' category, such as salmon, sardines, and canned light tuna, which are lower in mercury and high in beneficial omega-3s.

For all consumers:

Eat smaller fish: When possible, choose smaller, younger wahoo, as their mercury levels will be lower.
Diversify your diet: Incorporate a variety of low-mercury fish and shellfish to gain the nutritional benefits of seafood while minimizing mercury exposure.

Conclusion: Making an Informed Choice

Wahoo does have a lot of mercury compared to smaller, less predatory species, and is classified by health authorities as a fish to be consumed in moderation. For the average adult, including wahoo as part of a varied diet is generally safe, but should be limited to about one serving per week. For pregnant women, nursing mothers, and young children, stricter limits or avoidance is recommended due to the potential neurotoxic effects of methylmercury. By being mindful of consumption guidelines and choosing a variety of seafood, you can safely enjoy the delicious taste of wahoo while protecting your health.

The Mercury Question: Risk vs. Reward with Fish

For a broader understanding of how to balance fish consumption with mercury concerns, see this educational resource from the Harvard T.H. Chan School of Public Health: The Mercury Question: How to Understand Risk vs. Reward when Eating Fish.

Frequently Asked Questions

Yes, for most adults, wahoo is safe to eat in moderation, typically limited to one serving per week due to its moderate-to-high mercury content.

No, it is not recommended for pregnant women to consume wahoo or other high-mercury fish due to the risk of harming the fetus's developing brain and nervous system.

Wahoo generally has mercury levels similar to or higher than yellowfin tuna, but less than bigeye tuna and significantly more than canned light tuna.

No, cooking methods like baking or grilling do not significantly reduce the methylmercury that is bound to the protein in the fish's muscle tissue.

Excessive intake of high-mercury fish can lead to methylmercury poisoning, with symptoms that may include neurological issues such as tingling, muscle weakness, and impaired coordination.

Safer, lower-mercury fish options include salmon, sardines, anchovies, shrimp, and tilapia, which can be eaten more frequently.

Yes, methylmercury accumulates in the body with regular consumption of high-mercury fish, but the body can excrete it over several months with reduced intake.