Chilean sea bass isn’t dangerous in small amounts, but it carries enough mercury to warrant limiting how often you eat it. The FDA classifies it as a “Good Choice” rather than a “Best Choice” fish, meaning adults should stick to one serving per week, and pregnant or breastfeeding women should cap it at one 4-ounce serving per week. Beyond mercury, the fish raises environmental concerns that have put it on conservation watchlists for decades.
Mercury Levels in Chilean Sea Bass
Chilean sea bass contains an average of 0.354 parts per million (ppm) of mercury, with individual fish ranging from undetectable levels all the way up to 2.18 ppm. That upper end is well above the FDA’s 1.0 ppm action level for commercially sold fish. The wide range exists because mercury accumulates over a fish’s lifetime, and Chilean sea bass (technically called Patagonian toothfish) is a slow-growing, long-lived deep-water species. Older, larger fish concentrate far more mercury in their flesh than younger ones.
For context, fish on the FDA’s “Best Choices” list, like salmon, sardines, and tilapia, typically have mercury concentrations below 0.15 ppm. Chilean sea bass sits roughly two to three times higher than that average, which is why the FDA places it one tier down. You can safely eat it, but not as freely as lower-mercury options.
Who Needs to Be Most Careful
Mercury is a neurotoxin, and developing brains are especially vulnerable. The FDA advises pregnant and breastfeeding women to eat no more than one 4-ounce serving of Chilean sea bass per week, and to avoid combining it with other “Good Choice” fish that same week. Children need even smaller portions: about 1 ounce for toddlers ages 1 to 3, scaling up to 4 ounces by age 11. The FDA recommends children stick to the “Best Choices” list entirely, eating two servings per week from that lower-mercury tier.
For the average adult, occasional Chilean sea bass is fine. The concern grows when it becomes a regular part of your diet. Mercury leaves the body slowly, so frequent exposure lets it build up in your bloodstream over weeks and months. Symptoms of chronic low-level mercury exposure include fatigue, difficulty concentrating, numbness in the hands and feet, and mood changes. These are subtle enough that most people wouldn’t connect them to a fish they eat twice a week.
High Fat Content
Chilean sea bass is a notably fatty fish, with about 15 grams of total fat per 100-gram serving. That’s part of what makes it so popular in restaurants: the high fat content gives it a rich, buttery texture that holds up well to various cooking methods. Some of that fat comes from omega-3 fatty acids, which are genuinely beneficial for heart and brain health. But the total fat load is significantly higher than leaner white fish like cod, haddock, or tilapia, which typically contain 1 to 3 grams of fat per serving. If you’re watching your overall fat intake, Chilean sea bass is closer to salmon territory than to the light, flaky white fish most people picture.
Environmental Problems With the Fishery
The “bad for you” question extends beyond personal health for many people. Chilean sea bass became wildly popular in the 1990s, and the resulting demand drove widespread illegal, unregulated fishing that decimated populations in the Southern Ocean. International quotas now exist through CCAMLR (the Commission for the Conservation of Antarctic Marine Living Resources), which sets strict catch limits and requires boats to stop fishing once those limits are reached. Vessels must also relocate if they pull up more than one tonne of bycatch in a single haul.
The fishing method itself poses problems. Longline fishing for toothfish involves deploying millions of baited hooks. In 2002 alone, artisanal boats in southern Chile set 19.5 million hooks for Patagonian toothfish. These longlines are considered a primary threat to albatross and petrel populations worldwide. Seabirds dive for the bait as lines are being set, get hooked, and drown as the line sinks. While bycatch rates per hook are low (roughly 0.047 birds per 1,000 hooks in toothfish fisheries), the sheer number of hooks deployed makes the cumulative toll significant.
Not all Chilean sea bass is equal on sustainability. The fishery around South Georgia Island in the sub-Antarctic has earned Marine Stewardship Council (MSC) certification, meaning it meets specific standards for stock health and ecosystem impact. Seafood Watch recommends purchasing toothfish from MSC-certified sources. However, genetic testing of retail fish bearing MSC labels has revealed mislabeling, meaning some fish sold as sustainably caught may actually come from unregulated fisheries. The blue MSC label on packaging is your best available indicator, but it’s not a guarantee.
Lower-Risk Alternatives
If you love Chilean sea bass for its rich, meaty texture, several lower-mercury fish can fill a similar role. Salmon is the closest match in terms of fat content and omega-3s, with mercury levels typically one-fifth of Chilean sea bass. Black cod (sablefish) offers a similarly buttery quality. For lighter options, halibut, striped bass, and mahi-mahi all provide firm, satisfying fillets while falling lower on the mercury scale.
The FDA’s full “Best Choices” list includes dozens of species you can eat two to three servings of per week without concern: salmon, sardines, trout, shrimp, tilapia, pollock, cod, catfish, and scallops among them. Swapping even one weekly serving of Chilean sea bass for any of these meaningfully reduces your mercury exposure over time.