High Mercury Content: The Biggest Offenders
Larger, older predatory fish tend to accumulate higher levels of mercury throughout their lives, a process called bioaccumulation. This occurs because the mercury builds up in the fish's body faster than it can be eliminated. Excessive consumption of these fish can lead to mercury poisoning, which can cause brain and nerve damage in adults and severely affect the development of the nervous system in fetuses and young children.
Fish with Dangerous Mercury Levels
- King Mackerel: Especially those caught in the Pacific Ocean, are known for their very high mercury levels.
- Shark: As a top predator, shark meat contains extremely high concentrations of mercury and is also a severely overfished species.
- Swordfish and Marlin: Both are large, long-living predatory fish that pose a significant mercury risk and are often subject to overfishing.
- Orange Roughy: These fish, also called slimeheads, can live up to 150 years, giving them a long time to accumulate mercury and other contaminants. Their population is also severely depleted from overfishing.
- Tilefish (Gulf of Mexico): The Gulf of Mexico variety has some of the highest mercury levels measured in fish. Atlantic tilefish is a better, but still moderate, option.
- Bigeye and Ahi Tuna: These larger tuna species contain more mercury than smaller types, like skipjack or canned light tuna.
Contaminants and Pollutants: Why Sourcing Matters
Beyond mercury, seafood can be a source of other contaminants due to the environment it is harvested from or the practices used in aquaculture. This includes harmful chemicals like polychlorinated biphenyls (PCBs) and dioxins, as well as antibiotics and pesticides.
Farm-Raised vs. Wild-Caught Concerns
Concerns exist regarding some farm-raised seafood. These include the use of antibiotics and pesticides to control disease and parasites in crowded conditions, as well as the higher levels of PCBs found in some farmed fish compared to their wild counterparts. On the other hand, the mercury content in wild fish can also be a concern, depending on the species and harvest location. Consumers should always research the source and specific type of seafood they are purchasing.
Other Risky Seafood
- Escolar: Often mislabeled as "white tuna," this fish contains an indigestible wax ester called gempylotoxin. Consumption can cause a type of oily diarrhea known as keriorrhea, with symptoms that include severe abdominal cramps and nausea.
- Pufferfish (Fugu): This Japanese delicacy is lethally poisonous if not prepared correctly. Its organs contain tetrodotoxin, a neurotoxin 1,200 times more potent than cyanide, for which there is no known antidote. Only highly trained and licensed chefs should ever prepare fugu.
Unsustainable and Endangered Species
Choosing seafood responsibly also means considering the environmental impact. Overfishing can decimate fish populations and disrupt entire ecosystems. Reputable resources like the Monterey Bay Aquarium’s Seafood Watch program can guide consumers toward more sustainable options.
Endangered Species to Avoid
- Atlantic Bluefin Tuna: Highly prized and critically endangered due to decades of overfishing, this species should be avoided entirely.
- European Eel: Listed as critically endangered, this species has suffered a massive decline in population.
- Atlantic Halibut: With its population significantly depleted by commercial fishing, this species is considered endangered.
- Shark: In addition to high mercury, many shark species are listed as endangered due to overfishing for fins and meat.
- American Eel: This species is also on the endangered list, making it another one to avoid for sustainability.
A Comparison of Seafood Options
| Attribute | High-Risk Seafood (AVOID) | Better-Choice Seafood (EAT) |
|---|---|---|
| Mercury Content | King Mackerel, Shark, Swordfish, Bigeye/Ahi Tuna | Salmon, Sardines, Tilapia, Anchovies, Catfish |
| Sustainability | Atlantic Bluefin Tuna, European Eel, Atlantic Halibut | Alaskan Salmon (Wild), Pacific Sardines, Farmed Mussels and Oysters |
| Contaminants | Escolar (Keriorrhea), Atlantic Farmed Salmon (Higher PCBs) | Wild-caught fish from cleaner waters, responsibly farmed seafood |
| Toxicity | Pufferfish (Deadly tetrodotoxin if improperly prepared) | Non-toxic species; all seafood should be cooked properly |
| Primary Reason for Caution | Potential for brain/nerve damage, extinction risk | Excellent source of Omega-3s, lower contaminants, abundant populations |
Conclusion
Making mindful choices about seafood consumption is essential for both your personal health and the preservation of our marine ecosystems. By understanding the risks associated with certain species—from the neurotoxins in high-mercury predators to the environmental impact of unsustainable fishing—you can navigate the market more responsibly. Stick to smaller fish lower on the food chain, research your sources using guides like Monterey Bay's Seafood Watch, and always prioritize properly sourced and prepared options to ensure your dinner is both delicious and safe.
A Guide to Safer Shellfish Choices
While this article primarily focuses on finfish, it's also worth noting that not all shellfish are created equal. Oysters and mussels are often excellent choices from a sustainability standpoint, particularly when farmed, as they can even improve water quality. However, some crab species, particularly the blue crab from certain overfished areas, can be less sustainable. Furthermore, shellfish can accumulate heavy metals from the seabed, making sourcing important. Following regional consumption advisories is crucial for all seafood, including shellfish.
The Importance of Cooking Properly
Regardless of the type of seafood, proper handling and cooking are critical for safety. This is especially true for shellfish and for raw dishes like sushi. Always cook seafood to the recommended internal temperature to kill harmful bacteria and parasites. Never attempt to cook potentially toxic seafood like pufferfish at home without expert training. For raw fish dishes like sushi, ensure the fish has been properly frozen beforehand to eliminate parasites.
Making a Positive Impact
Your choices as a consumer have a direct impact on the health of our oceans. By avoiding endangered species and opting for sustainable alternatives, you contribute to preserving marine life for future generations. Supporting responsible fisheries and aquacultures helps drive the industry toward better practices. Educating yourself and others is the first step toward a healthier planet and a healthier you.
