Why some fish are off the menu
Making informed choices about the fish we consume goes beyond simply liking the taste. Several critical factors influence whether a particular species is safe, healthy, or environmentally responsible to eat. By understanding these reasons, you can navigate the seafood market with confidence.
The dangers of mercury contamination
Mercury is a naturally occurring element that, through industrial pollution, finds its way into waterways and oceans. In water, it's converted into methylmercury, a potent neurotoxin that accumulates in fish. Large, predatory fish at the top of the food chain accumulate the highest concentrations of mercury over their long lifespans. For most healthy adults, small amounts of mercury aren't a significant concern, but certain populations are highly vulnerable.
- Vulnerable populations: Pregnant women, women who are planning a pregnancy, nursing mothers, and young children should be especially cautious about mercury exposure. The developing nervous system of an unborn baby or young child is particularly sensitive to its harmful effects.
- Fish to avoid: To reduce exposure, the FDA and EPA advise against eating fish with the highest mercury levels. This list includes shark, swordfish, king mackerel, marlin, and tilefish from the Gulf of Mexico.
The ecological impact of unsustainable seafood
Overfishing and destructive fishing practices threaten the health of our oceans and the survival of marine species. When certain fish stocks are depleted, it can disrupt entire ecosystems. To promote ocean health, it's important to be mindful of unsustainable choices.
- Overfished species: Certain species are at high risk due to overfishing. This list often includes Atlantic bluefin tuna, European eel, and Atlantic cod. Organizations like the World Wildlife Fund (WWF) provide guides to help consumers identify at-risk populations.
- Destructive harvesting methods: Some fishing methods can harm the environment by causing high levels of bycatch (the unintentional capture of other marine life) or destroying crucial habitats. Consumer guides, such as the Monterey Bay Aquarium's Seafood Watch, offer recommendations on which types of fish are caught using sustainable methods.
Understanding naturally occurring toxins and pollutants
Beyond mercury, some fish can contain other toxins that pose a risk to human health. These can be naturally occurring or a result of environmental pollution.
- Pufferfish: This fish contains tetrodotoxin, a deadly neurotoxin. Properly trained and licensed chefs can prepare it as a delicacy (fugu), but it is never safe to prepare at home.
- Ciguatera poisoning: This occurs from eating fish that have consumed a certain type of algae. Large reef fish like barracuda, grouper, and amberjack are most often associated with this poisoning, and the toxins are not destroyed by cooking.
- PCBs and dioxins: These industrial pollutants can build up in the fatty tissues of fish. Like mercury, they bioaccumulate up the food chain. State and local fish advisories often warn against consuming certain species from specific water bodies due to contamination from these chemicals.
Low vs. High-Risk Fish: A Comparison
To simplify your seafood choices, here is a comparison of some commonly available fish based on general health and sustainability factors. For the most precise information, always consult a reliable seafood guide from your region.
| Feature | Lower-Risk Choices | Higher-Risk Choices |
|---|---|---|
| Mercury Content | Salmon, sardines, shrimp, scallops, canned light tuna, tilapia, cod, pollock, anchovies, herring. | Shark, swordfish, king mackerel, bigeye tuna, marlin, orange roughy, tilefish (Gulf of Mexico). |
| Sustainability | Farmed mussels and oysters, farmed US tilapia, wild Alaska salmon, and Pacific halibut are often considered good choices. | Atlantic bluefin tuna, European eel, and Atlantic cod are often overfished and considered unsustainable. |
| Toxin Risk | Properly sourced and cooked fish from trusted providers pose minimal risk. | Pufferfish, barracuda, and other large reef fish can carry ciguatera toxin. Improperly stored scombridae fish (like tuna and mackerel) risk histamine poisoning. |
| Parasite Risk | Properly cooked fish has very low parasite risk. Farmed fish generally have lower risk of parasites than wild-caught. | Eating raw or undercooked wild-caught fish, especially salmon, increases risk of parasites like roundworms. |
Making smart seafood choices
To make the most responsible and healthy choices, follow these best practices:
- Prioritize smaller fish: Fish lower on the food chain, such as sardines and anchovies, have less time to accumulate toxins like mercury.
- Use regional seafood guides: Use resources from organizations like the Monterey Bay Aquarium Seafood Watch, which provide region-specific guidance on sustainable and safe options.
- Choose farmed wisely: Not all farmed fish are created equal. Choose farmed seafood that is certified as sustainable by a reputable organization.
- Check local advisories: For fish caught in local rivers or lakes, check with your local or state health department for specific consumption advisories.
- Always cook thoroughly: Cooking fish to the proper internal temperature will kill parasites and bacteria. Pregnant women, in particular, should avoid uncooked or undercooked fish and shellfish.
- Diversify your diet: By eating a variety of fish and shellfish low in mercury, you can reap the nutritional benefits while minimizing your exposure to any single contaminant.
Conclusion
While fish offers valuable nutrients like omega-3 fatty acids, it's crucial to be aware of the risks associated with certain species. By understanding what fish do we not eat, including those high in mercury, at risk of overfishing, or susceptible to toxins, you can protect your health and support sustainable ocean practices. Relying on trusted resources and choosing smaller, lower-risk fish will allow you to enjoy the benefits of seafood responsibly. Ultimately, making conscious and educated decisions is the best way to ensure your dietary choices are both healthy and ethical.
For more detailed information on specific species and current guidelines, a useful resource is the FDA's official advice on eating fish.
