17 Fish You Should Avoid Eating (And Here’s Why)
Ever wonder if that fish on your plate is a good choice? Not all seafood is created equal when it comes to your health and our oceans.
Some fish contain dangerous levels of mercury and other toxins, while others are being fished to the brink of extinction.
Making smart seafood choices protects both your family’s health and our marine ecosystems.
1. King Mackerel: The Mercury Monarch
Swimming in warm Atlantic waters, this predatory fish accumulates alarming levels of mercury throughout its lifetime. The FDA specifically warns pregnant women, nursing mothers, and children to avoid it completely.
Over time, consuming king mackerel can damage your nervous system and brain development. The oceans suffer too—overfishing has depleted populations in many regions, creating ripple effects throughout marine food chains.
2. Shark: Apex Predator, Maximum Risk
Those shark fin soups and steaks come with a hefty price tag, for both you and the ocean. As top predators, sharks accumulate extraordinarily high mercury levels that can harm your brain and nervous system.
Shark populations face catastrophic decline due to finning practices and overfishing. Their slow reproduction rates—some species take 15+ years to reach maturity—mean these magnificent creatures can’t bounce back quickly from fishing pressure.
3. Swordfish: The Mercury Sponge
That impressive swordfish steak might look appetizing, but it’s essentially a mercury sponge on a plate. These magnificent ocean giants live long lives, giving them plenty of time to absorb concerning levels of contaminants.
The FDA and EPA place swordfish in their highest-risk category. The fishing methods used to catch them—primarily longlines—also snag endangered sea turtles, sharks, and seabirds as accidental bycatch, creating a double environmental whammy.
4. Gulf Tilefish: Hidden Toxic Treasure
Lurking at the top of the FDA’s mercury warning list, Gulf tilefish contain some of the highest mercury concentrations of any seafood. These colorful bottom-dwellers from the Gulf of Mexico accumulate toxins from their habitat and prey.
Pregnant women and children should never eat tilefish. Destructive bottom trawling methods used to catch them also damage fragile seafloor ecosystems, crushing coral reefs and disrupting marine habitats that took centuries to form.
5. Orange Roughy: The Centenarian Fish
Would you eat something older than your grandparents? Orange roughy can live up to 150 years, which means they’ve had decades—even centuries—to accumulate toxins and mercury in their fatty tissues.
These deep-sea dwellers grow and reproduce at glacial speeds. When you order orange roughy, you’re potentially eating a fish that was swimming when your great-grandparents were born! This slow life cycle makes them extraordinarily vulnerable to overfishing.
6. Atlantic Bluefin Tuna: Endangered Delicacy
That premium sushi roll might be your last taste of a vanishing species. Atlantic bluefin tuna populations have plummeted by over 80% since 1970, pushing these magnificent creatures toward extinction.
Beyond the ecological disaster, their flesh contains dangerous levels of mercury and PCBs. These magnificent fish can weigh up to 1,500 pounds and swim at 40 mph, yet they can’t outrace the devastating effects of overfishing and illegal poaching fueled by sky-high prices.
7. Bigeye Tuna: Mercury Magnet
Popular in high-end sushi restaurants, bigeye tuna packs a double punch of environmental and health concerns. Its dark, fatty flesh, prized by chefs, accumulates significantly more mercury than lighter tuna varieties.
Bigeye populations continue declining in tropical and subtropical waters worldwide. The fishing methods used to catch them frequently ensnare dolphins, sharks, and sea turtles as bycatch. Think twice before ordering that toro sashimi—it comes with hidden costs.
8. Farmed Atlantic Salmon: Pink Deception
That vibrant pink color? Often artificial dyes added to the feed. Farmed Atlantic salmon are raised in crowded open-net pens where disease spreads rapidly, requiring antibiotics and pesticides that end up in your dinner.
These fish contain elevated levels of PCBs and significantly more inflammatory omega-6 fatty acids than their wild counterparts.
The waste from salmon farms pollutes surrounding waters, threatening wild salmon populations and other marine life with parasites and contamination.
9. Imported Shrimp: Tiny Shellfish, Enormous Problems
Shrimp cocktail lovers beware—90% of shrimp consumed in America comes from overseas farms with shocking health violations. Testing regularly reveals banned antibiotics, E. coli, salmonella, and chemical residues that U.S. inspectors rarely catch.
The environmental toll is equally disturbing. Shrimp farming in Asia has destroyed over 38% of the world’s mangroves—crucial nurseries for marine life and natural storm barriers.
Just one pound of farmed shrimp creates an estimated ten pounds of environmental damage.
10. Imported King Crab: Royal Impostor
That “Alaskan” king crab on the menu? Often, a Russian impostor caught using unsustainable practices in the Barents Sea. Mislabeling runs rampant in the seafood industry, and king crab is among the worst offenders.
Russian king crab fisheries lack the strict management of Alaskan operations. Overfishing threatens wild populations, while processing facilities often employ questionable practices.
When you see suspiciously cheap king crab legs, they’re almost certainly imported and problematic.
11. Chinese Farmed Tilapia: Dirty Little Secret
Once hailed as an affordable protein source, Chinese tilapia farms have become notorious for horrifying practices. Fish are often raised in ponds fertilized with animal manure and treated with prohibited chemicals and antibiotics.
Nutritionally, these fish offer little benefit—they contain minimal omega-3s but high levels of inflammatory omega-6 fatty acids.
Environmental investigations have found Chinese tilapia farms routinely discharging untreated waste directly into rivers and drinking water supplies.
12. Atlantic Cod: Ecological Collapse in a Sandwich
Remember when fish and chips always meant cod? Overfishing triggered one of history’s most dramatic fishery collapses in the 1990s, when Atlantic cod populations crashed by 99% in some areas.
Despite fishing restrictions, many Atlantic cod populations remain at historically low levels. The ecological ripple effects continue decades later, as predator-prey relationships throughout North Atlantic food webs remain disrupted.
That cod sandwich represents a cautionary tale of marine mismanagement.
13. Non-Certified Chilean Sea Bass: The Pirate’s Prize
Known as “white gold” to illegal fishermen, non-certified Chilean sea bass (actually Patagonian toothfish) remains one of the ocean’s most pirated species. These deep-sea dwellers contain concerning mercury levels due to their position at the top of the Antarctic food chain.
Illegal fishing operations target these valuable fish, often using destructive longlines that annihilate thousands of albatrosses and other seabirds annually. Populations have been so decimated that scientists fear they may never fully recover.
14. Farmed Freshwater Eel: Slippery Ethics
That unagi sushi roll comes with serious baggage. Freshwater eels cannot be bred in captivity—wild baby eels (glass eels) are captured, then raised in farms where they accumulate PCBs and mercury from polluted environments.
Wild eel populations have crashed by over 90% in some regions. The glass eel trade has become so lucrative that it’s created black markets worth billions, complete with eel smuggling rings and violence.
Some scientists predict European eels may be extinct within decades.
15. Marlin: Magnificent but Menacing
Hemingway’s famous fish packs a toxic punch. Both blue and striped marlin contain mercury levels so high that a single serving exceeds weekly safety limits for adults.
These spectacular billfish are also struggling against extinction due to overfishing. Their capture typically involves longlines stretching up to 60 miles, which unintentionally hook endangered sea turtles, sharks, and seabirds.
When marlin populations decline, entire open-ocean ecosystems suffer imbalances.
16. Escolar: The Ex-Lax Fish
Ever heard of keriorrhea? This embarrassing condition—explosive, oily orange diarrhea—is escolar’s special gift to unsuspecting diners. The culprit is indigestible wax esters that accumulate in the fish’s flesh.
Escolar is frequently mislabeled as “white tuna” or “super white tuna” in sushi restaurants, leaving customers unaware of potential digestive distress. Japan and Italy have banned escolar outright, while the FDA merely “advises against” serving it.
When you see suspiciously white, buttery tuna, proceed with caution!
17. Imported Catfish: Filthy Imposters
Those bargain “catfish” fillets from Vietnam (labeled as swai, basa, or tra) swim in some truly disgusting conditions. FDA inspections have repeatedly found banned antibiotics, chemicals, and filth, including rodent hair and insect parts.
Vietnamese catfish farms routinely discharge untreated waste directly into the Mekong River. U.S. inspection of imported catfish is notoriously lax—less than 2% gets screened.
Meanwhile, domestic catfish farmers must meet strict safety standards, creating an uneven playing field.