There is no universal list of fish that nobody should ever order. A better approach is to consider mercury levels, sourcing, freshness, and how often you eat a particular species.
The FDA places seven fish in its highest-mercury “Choices to Avoid” category: shark, swordfish, king mackerel, marlin, orange roughy, Gulf of Mexico tilefish, and bigeye tuna. This advice is especially important for pregnant or breastfeeding people, those who may become pregnant, and young children.
Three additional restaurant choices deserve questions rather than an automatic ban:
8. Imported farmed shrimp: Farming and labor standards vary considerably, so ask where it came from.
9. Atlantic salmon: Sustainability depends heavily on the farming location and method. Some certified sources are recommended, while other operations receive poor environmental ratings.
10. Unidentified “sea bass” or “whitefish”: These broad menu labels can describe different species. Ask the server for the exact fish and its origin before ordering.
Sustainability ratings are based on the fishery or farm—not simply the species name. Seafood Watch classifies options according to management, environmental effects, overfishing, and harm to other marine life.
Fish remains a nutritious food, and the EPA encourages people to choose varieties lower in mercury rather than avoiding seafood entirely.