Chilean sea bass is a nutritious fish, rich in omega-3 fatty acids, protein, and several key vitamins. It does carry moderate mercury levels, though, which means you’ll want to limit how often you eat it. The FDA categorizes it as a “Good Choice” fish, recommending no more than one serving per week.
What’s in a Serving
Chilean sea bass is not actually a bass. It’s a Patagonian toothfish, a large deep-water species found in some of the coldest ocean waters on Earth. That frigid habitat is exactly why the fish is so rich in fat: its body stores dense layers of oil to survive near-freezing temperatures, giving it the buttery, mild-flavored flesh that made it a restaurant staple.
A 100-gram serving (roughly 3.5 ounces) delivers around 124 calories and 18 grams of protein. That protein-to-calorie ratio is solid, though the fish is fattier than leaner options like cod or tilapia. The fat it carries is mostly the beneficial kind. Omega-3 fatty acids make up a significant portion of its total fat content, which is the main nutritional selling point.
Beyond the macros, a 100-gram serving provides about 70% of the daily value for vitamin B12, 45% for selenium, and 10% for vitamin D. B12 is essential for nerve function and red blood cell production. Selenium acts as an antioxidant and supports thyroid health. Vitamin D, which many people run low on, is hard to find in food outside of fatty fish and fortified products, so even 10% of the daily value from a single serving adds up.
Omega-3s and Heart Health
The omega-3 fatty acids in Chilean sea bass benefit your cardiovascular system in several ways. They lower triglycerides (a type of blood fat linked to heart disease), reduce the risk of irregular heartbeat, slow the buildup of artery-clogging plaque, and modestly lower blood pressure. These effects are well established and apply broadly to fatty fish consumption, not just this species.
For context, wild-caught salmon delivers about 1,210 milligrams of omega-3s per 3-ounce serving. Chilean sea bass is also omega-3 rich due to its high fat content, though salmon remains the gold standard for omega-3 density. If you’re eating fish specifically for heart health, both are strong choices, but salmon gives you more omega-3s with far less mercury.
The Mercury Tradeoff
This is where the picture gets more complicated. Chilean sea bass has a mean mercury concentration of 0.354 parts per million, based on FDA testing data. That’s roughly 16 times higher than fresh or frozen salmon, which averages just 0.022 ppm. It’s not in the highest-risk category (swordfish, shark, and king mackerel are all worse), but it’s elevated enough to matter.
The FDA places Chilean sea bass in its “Good Choices” tier rather than the “Best Choices” tier. The practical difference: you should eat no more than one serving per week from the “Good Choices” list. A serving is roughly the size of your palm, or about 4 ounces for pregnant or breastfeeding women. If you’re eating other moderate-mercury fish that same week, like tuna or mahi-mahi, that counts toward the same weekly limit.
Mercury accumulates in your body over time, and the concern is greatest for developing brains. Pregnant women, breastfeeding mothers, and young children should be the most careful about staying within the one-serving-per-week guideline for this fish. For other adults, occasional consumption poses minimal risk, but making Chilean sea bass your everyday protein source would not be wise.
MSC-Certified Fish Has Less Mercury
Not all Chilean sea bass carries the same mercury load, and where the fish was caught matters significantly. A study published in PubMed Central found that retail fish labeled as MSC-certified (Marine Stewardship Council) had, on average, only half the mercury of uncertified fish.
The geographic differences are striking. Fish from the South Georgia and Shag Rocks stock in the South Atlantic averaged just 0.23 ppm of mercury, while fish sourced from waters near Chile carried more than three times that amount at 0.73 ppm. That’s a huge range, and it means that choosing MSC-certified Chilean sea bass isn’t just a sustainability decision. It’s a health decision too.
There is a complication, though. The same study found that seafood mislabeling and stock substitutions can obscure these patterns. Some fish sold as MSC-certified had mercury levels on par with uncertified fish from higher-mercury regions. Buying from reputable retailers who can trace their supply chain gives you the best chance of getting what the label promises.
How It Compares to Salmon
If you’re choosing between Chilean sea bass and salmon purely on health merits, salmon wins on most counts. Wild-caught salmon delivers more omega-3s per serving, carries negligible mercury (0.022 ppm versus 0.354 ppm), and falls into the FDA’s “Best Choices” category, meaning you can safely eat two to three servings per week instead of just one. Salmon is also typically less expensive.
Where Chilean sea bass has an edge is flavor and texture. Its buttery, rich flesh appeals to people who dislike “fishy” tasting fish, making it a gateway for those who wouldn’t otherwise eat seafood at all. If the choice is between Chilean sea bass once a week and no fish at all, the sea bass is clearly the healthier option. Getting omega-3s from a moderate-mercury fish is better than skipping fish entirely.
For people who enjoy both, a practical approach is to eat salmon as your regular fish and treat Chilean sea bass as an occasional indulgence, keeping it to once a week at most and looking for the MSC-certified label when you buy it.