Understanding the Confusion Around "Dory" Fish
When people ask, “is Dory fish high in mercury?” they are often confused by the varying types of fish that are marketed under this name. The animated movie Finding Nemo featured a character named Dory, who was a Pacific regal blue tang (Paracanthurus hepatus). This species is an ornamental fish kept in aquariums and is not eaten. In the culinary world, the term 'Dory' typically refers to one of two different fish, and their mercury content varies significantly.
John Dory: A Low-Mercury Choice
The true John Dory, or Zeus faber, is a saltwater fish with delicate, white, sweet-tasting flesh that is highly prized for cooking. Unlike predatory fish at the top of the food chain, John Dory is not considered a high-mercury species. Multiple sources confirm that John Dory is a low-mercury option and safe for regular consumption. A study found a median mercury level of just 0.17 mg/kg (or ppm), placing it well within safe limits.
Basa Fish (Cream Dory): A Different Concern
A common, and often less expensive, substitute for John Dory is the Basa fish (Pangasius bocourti), an Asian catfish species frequently sold under names like 'Pacific Dory' or 'Cream Dory'. While Basa is also generally considered a low-mercury fish, its mercury levels have raised concerns due to its farming practices. Some research has shown that Basa, while within safe limits, can have contaminants based on its environment. For example, the FDA includes catfish on its list of 'Best Choices' for low-mercury fish, but the farming conditions of some imports can be controversial.
Factors Affecting Mercury Levels
Mercury levels in fish are not determined by species alone but are also influenced by several environmental factors. These factors can help explain why some fish contain more mercury than others.
- Position in the Food Chain (Biomagnification): Mercury accumulates up the food chain. Larger, predatory fish eat many smaller fish, absorbing their mercury. This process, called biomagnification, is why apex predators like shark and swordfish have higher mercury levels.
- Age and Size: Older and larger fish have had more time to accumulate mercury in their tissues. This is a key reason why John Dory, which is not an exceptionally large fish, has low mercury levels.
- Environment: The specific water body a fish inhabits can affect its mercury load, especially in freshwater fish. Some local areas may have advisories for mercury.
Comparison Table: John Dory vs. Basa (Cream Dory)
| Feature | John Dory (Zeus faber) | Basa (Pangasius bocourti) |
|---|---|---|
| Mercury Level | Low | Low, but varies depending on farming source |
| Origin | Wild-caught, found in coastal waters worldwide | Farmed, freshwater catfish from Southeast Asia |
| Flavor | Delicate, sweet, and mild | Mild and flaky, sometimes sold as a cheaper alternative |
| Consumer Warning | No specific warnings for regular consumption | Some concerns regarding farming practices, should be purchased from reputable sources |
Choosing Low-Mercury Seafood Options
To ensure a low mercury intake while enjoying the benefits of fish, it's wise to choose from a variety of low-mercury options. The FDA and EPA provide guidance on which fish are considered 'Best Choices,' allowing for 2-3 servings per week.
- Best Choices (Low Mercury):
- Salmon (wild Alaskan)
- Shrimp
- Sardines
- Tilapia
- Cod
- Catfish
- Haddock
- Good Choices (Moderate Mercury):
- Albacore tuna (canned, limited to 1 serving per week)
- Mahi Mahi
- Choices to Avoid (High Mercury):
- Shark
- Swordfish
- King Mackerel
- Marlin
- Orange Roughy
Conclusion
Ultimately, whether a specific Dory fish is high in mercury depends on the species. The true John Dory is a safe, low-mercury option, while the Basa fish often labeled as 'Cream Dory' remains a relatively low-mercury choice, although its quality and contaminant levels can be influenced by farming conditions. Consumers should be mindful of the label to distinguish between these species. By choosing a variety of low-mercury seafood, like John Dory and other options listed by the FDA, consumers can enjoy the nutritional benefits of fish while minimizing their mercury exposure.
For authoritative advice on mercury levels and seafood consumption, the U.S. Food and Drug Administration provides comprehensive guidance on its website: https://www.fda.gov/food/consumers/advice-about-eating-fish.
