The safest fish to eat are small, short-lived species that sit low on the food chain: salmon, sardines, anchovies, herring, and shrimp. These fish accumulate very little mercury because they don’t live long enough or eat enough smaller fish for the metal to build up in their tissues. Shrimp contains just 0.009 ppm of mercury on average, and salmon comes in at 0.022 ppm, both far below the levels found in larger predatory fish like swordfish or shark.
The “Best Choices” List
The FDA and EPA jointly maintain a three-tier ranking of fish based on mercury content. The “Best Choices” category includes more than 30 species you can safely eat two to three servings per week. Among the most widely available options on that list: salmon, shrimp, cod, catfish, tilapia, pollock, flounder, sole, sardines, anchovies, herring, canned light tuna (skipjack), trout, clams, scallops, and crab.
A second tier, “Good Choices,” includes fish with moderate mercury levels that are safe at one serving per week. This group covers halibut, mahi mahi, snapper, grouper, albacore tuna, and yellowfin tuna. The difference is real: canned albacore tuna averages 0.350 ppm of mercury, nearly three times the 0.126 ppm found in canned light tuna.
A small number of fish should be avoided entirely, especially by pregnant women and young children. These include shark, swordfish, king mackerel, and tilefish from the Gulf of Mexico. These large, long-lived predators accumulate mercury throughout their lifetimes and consistently test at the highest levels.
The Best Nutrient-to-Risk Ratio
If you want to maximize the health benefits of fish while minimizing contaminant exposure, five species stand out. Nutritionists sometimes call them the “SMASH” fish: sardines, mackerel (canned or Atlantic), anchovies, salmon, and herring. California’s Office of Environmental Health Hazard Assessment specifically flags these five as having both the lowest mercury levels and the highest concentrations of omega-3 fatty acids.
This combination matters because omega-3s are the main reason health guidelines recommend eating fish in the first place. They reduce inflammation, support heart health, and play a critical role in brain development. Getting those benefits from a fish that also happens to carry minimal mercury makes these five species the practical sweet spot. Salmon is the easiest to find in most grocery stores, while canned sardines and anchovies are inexpensive and shelf-stable.
Farmed vs. Wild-Caught Fish
The farmed-versus-wild debate mostly centers on salmon, the most popular fish in the U.S. Both are safe to eat, but they carry different contaminant profiles. Farm-raised Atlantic salmon has significantly higher concentrations of dioxins, PCBs, and certain pesticides compared to wild Pacific salmon. The gap is especially pronounced in European-farmed salmon, which tests higher in these industrial pollutants than salmon farmed in North or South America.
Wild-caught salmon tends to be leaner and lower in total contaminants. If you eat salmon frequently (more than once a week), choosing wild-caught Alaskan varieties like sockeye or pink salmon reduces your cumulative exposure. If you eat it once a week or less, the difference is small enough that either option falls well within safe limits.
Shellfish Safety
Clams, oysters, mussels, and scallops are generally low in mercury and appear on the FDA’s “Best Choices” list. Their primary contaminant concern is different from finfish: bivalves filter large volumes of water and can accumulate heavy metals like cadmium and lead from their environment. Oysters and shrimp tend to have relatively higher cadmium levels than clams, though commercially sold shellfish in the U.S. are tested against FDA action limits and rarely exceed them.
Pacific shellfish tend to carry slightly more cadmium than Atlantic shellfish due to natural ocean chemistry. Buying from reputable sources and sticking to commercially harvested shellfish (rather than recreationally gathered) is the simplest way to reduce risk, since commercial operations are subject to regular monitoring for both heavy metals and harmful algal toxins.
Freshwater Fish Carry Extra Risks
Fish caught recreationally from lakes, rivers, and streams often carry higher contaminant loads than commercially sold seafood. This includes not just mercury but also PFAS, the persistent “forever chemicals” found in many waterways. Most existing research on PFAS in fish has focused on freshwater species, and concentrations can be high enough that some state health departments advise limiting consumption of locally caught fish.
If you fish recreationally, check your state’s fish consumption advisories before eating your catch. These advisories are updated based on local testing and can vary dramatically from one body of water to another, even within the same county.
How Cooking Reduces Contaminants
Certain contaminants, particularly PCBs and dioxins, concentrate in the fatty tissue of fish. Simple preparation steps can cut your exposure to these fat-soluble pollutants by up to 50%. Remove the skin and any visible fat before cooking. Choose grilling, broiling, or baking over frying, and let the fat drip away during cooking rather than collecting it. Eat the fillet only, and skip using the drippings for sauces or gravy.
These steps matter most for fattier fish like farmed salmon, bluefish, or lake trout. For lean, low-contaminant species like cod, tilapia, or shrimp, preparation method makes less of a difference because there’s little fat to harbor pollutants in the first place.
Serving Sizes for Children and Pregnancy
The FDA recommends that pregnant and breastfeeding women eat two to three servings of “Best Choices” fish per week. One adult serving is about 4 ounces, roughly the size of the palm of your hand. For children, servings are smaller: about 1 ounce for ages 1 to 3, 2 ounces for ages 4 to 7, and 3 ounces for ages 8 to 10.
Children and developing fetuses are more sensitive to mercury’s effects on the nervous system, which is why the species selection matters more for these groups. Sticking to the SMASH fish or shrimp keeps mercury exposure minimal while still delivering the omega-3s that support brain development. The goal is not to avoid fish during pregnancy, but to choose the right ones.