Mercury in Fish: Health Risks, High-Mercury Species & Safe Eating Guidelines

Methylmercury, a potent neurotoxin, accumulates in fish and shellfish. Fetuses, infants, and young children are most vulnerable—exposure impairs cognitive development, memory, attention, language, and motor skills. Adults can experience neurologic symptoms (paresthesia, ataxia, vision/hearing changes) at high exposures.

How Mercury Enters Seafood

Inorganic mercury from coal combustion, mining, and industrial emissions settles in waterways. Microorganisms convert it to methylmercury, which bioaccumulates up the food chain. Large, long-lived predatory fish have the highest levels.

Fish to AVOID (Highest Mercury)

Pregnant women, those planning pregnancy, nursing mothers, and children <6 years should not eat these:

• King mackerel
• Marlin
• Orange roughy
• Shark
• Swordfish
• Tilefish (Gulf of Mexico)
• Bigeye tuna (often sold as ahi, sushi-grade)

Fish to LIMIT (Moderate Mercury)

No more than 1 serving/week (4 oz adult, 1–2 oz child) for sensitive groups:

• Albacore (white) tuna (canned or fresh)
• Grouper, Halibut, Mahi-mahi, Spanish mackerel, Snapper, Striped bass, Bluefish, Chilean sea bass
• Walleye, pike, bass (freshwater—check local advisories)

Best Choices (Lowest Mercury) — Eat 2–3 Servings/Week

• Salmon (wild or farmed)
• Shrimp, scallops, crab, clams, oysters, mussels
• Canned light tuna (skipjack)
• Pollock, tilapia, catfish, cod, haddock, flounder, sole
• Anchovies, sardines, herring
• Trout (farmed)

Practical Tips to Reduce Exposure

• Vary your seafood: Don't eat the same type daily.
• Choose smaller, younger fish: Lower on food chain = less mercury.
• Check local advisories: For recreationally caught fish (EPA/fish advisories by state).
• Cooking doesn't remove mercury: It's bound to protein, not fat. Trimming fat helps with PCBs/dioxins, not mercury.
• Rinsing canned tuna: Minimal effect; mercury is in the flesh.

Special Populations

• Pregnancy/Preconception: FDA/EPA recommend 8–12 oz/week of low-mercury fish for fetal brain development (omega-3s). Avoid high-mercury species entirely.
• Children: 2 servings/week of best choices, portion size by age.
• General adults: Benefits of fish (protein, omega-3s, selenium, vitamin D) outweigh risks if following guidelines.

Resources: FDA/EPA Advice About Eating Fish | EPA Mercury in Fish