Revised February 2025
Polluted Oceans Mean Toxic Fish
Oceans today are increasingly contaminated with mercury and other toxic metals, microplastics and toxic chemicals. Just as we absorb the toxins from the air we breathe, the water we drink, and the food we eat, fish absorb (and accumulate) toxins as well. The more polluted the water, the more polluted the fish who live and hunt in that water.
Fish remain one of the few natural sources of the essential Omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Fish obtain these by consuming algae—the only true source of EPA and DHA.
Benefits of EPA and DHA
These Omega-3 fatty acids (specifically EPA and DHA) are anti-inflammatory, reduce the occurrence of blood clots, increase skin collagen production, and support the structural integrity of cell membranes.
DHA, in particular, is essential for brain function and development. Babies born to mothers who supplemented with DHA during pregnancy tend to have better brain function, and research shows that higher levels of EPA and DHA can improve cognitive function, particularly in older adults. Deficiencies in DHA have been linked to conditions such as Multiple Sclerosis and cognitive decline.
Note: Because EPA and DHA reduce inflammation and blood clotting, there are times when one should stop eating fish and/or supplementing with EPA-DHA, such as after a wound or before surgery, when inflammation and clotting are necessary for healing.
Wild-Caught Versus Farm-Raised
While fish are an excellent source of EPA and DHA, it’s essential to select wild-caught species rather than farm-raised ones. Farmed fish often lack these vital nutrients due to unnatural diets that exclude algae, the primary source of EPA and DHA. The crowded conditions in fish farms also make the fish more susceptible to parasites and diseases, leading to the use of antibiotics and extreme chemicals, which further reduce their nutritional value and pose health risks. In some cases, farmed fish even have different appearances; for example, farmed salmon have a greyish color, while wild salmon’s natural pink or red hue comes from eating krill. Farm-raised salmon are fed colorants to mimic the natural color of their wild counterparts.
Certain wild-caught fish species not only have higher levels of EPA and DHA but also lower mercury content, making them a safer and more nutrient-rich choice for those looking to boost their Omega-3 intake. Opting for wild-caught fish from cleaner waters also helps avoid the nutrient deficiencies and contaminants commonly found in farm-raised fish. When we say “cleaner waters”, it’s hard to know what that means. The dirtiest and most farmed oceans are East Asian, off of China, India and Indonesia. The cleanest waters tend to be the North Pacific.
Best and Worst Fish
Predatory fish (like shark, swordfish and tuna) not only get mercury from the water, but eat other fish and collect their mercury. Additionally, fish who tend to frequent deeper water where mercury accumulates more will have more exposure. To make it easier for everyone, we have compiled a list of healthiest and least healthy fish below.
These are sorted from fish with the highest EPA and DHA and lowest mercury at the top, to fish with the lowest EPA and DHA and highest mercury at the bottom.
If you are supplementing with EPA and DHA, you can enjoy any of the fish with low mercury content (from the blue, green or yellow zones) and continue to supplement. If you are trying to get your EPA and DHA from fish, select options closer to the top (blue and green zones) to maximize EPA/DHA and minimize mercury exposure.
Remember to always get wild-caught fish, ideally from North Pacific (avoid Asian/Indian Oceans). Do not undercook. Do not eat old fish or fish that smells bad.
| Fish | Mg of Omega-3 | Mcg of Mercury |
|---|---|---|
| Salmon: Atlantic, Chinook, Coho | 1200 | 2 |
| Sardines: Atlantic and Pacific | 1100 | 2 |
| Salmon: Pink and Sockeye | 700 | 2 |
| Anchovies, Herring and Shad | 2300 | 10 |
| Mackerel: Atlantic and Pacific | 1350 | 13 |
| Pollock: Atlantic and Walleye | 600 | 6 |
| Trout: Freshwater | 1000 | 11 |
| Tilapia | 150 | 2 |
| Flounder, Plaice and Sole (Flatfish) | 350 | 7 |
| Haddock and Hake | 200 | 5 |
| Tuna: Bluefin and Albacore | 1700 | 58 |
| Tuna: White (Albacore), Canned | 1000 | 40 |
| Marlin, Striped | 1030 | 69 |
| Cod: Atlantic and Pacific | 200 | 14 |
| Catfish | 100 | 7 |
| Tuna: Light canned | 150 | 13 |
| Shark | 1250 | 151 |
| Swordfish | 1000 | 147 |
| Tilefish from the Gulf of Mexico | 1000 | 219 |
| Mackerel: King | 450 | 110 |
| Marlin, Blue | 250 | 69 |
| Tuna: Skipjack and Yellowfin | 150 | 49 |
| Orange Roughy (aka Deep Sea Perch) | 42 | 80 |
Source: https://stvincents.org/about-us/news-press/news-detail?articleid=26837&publicId=745