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10 Fish You Might Want to Think Twice About Ordering at a Restaurant

Seafood can be a nutritious addition to your diet, but mercury levels, sourcing practices, freshness, and sustainability all deserve a closer look before you order.

A friend who works in a seafood restaurant once told me something that completely changed the way I looked at a fish menu.

He explained that when he eats out, he doesn't automatically choose the fish with the most familiar name, the highest price, or the most attractive description. Instead, he considers where the fish came from, how it was caught or raised, how it was handled, and whether there are any health or environmental concerns associated with that particular species.

His advice was surprisingly simple: don't judge seafood by its name alone.

That conversation stayed with me because fish has long enjoyed a reputation as one of the healthiest foods available. And for good reason. Many fish provide high-quality protein, omega-3 fatty acids, vitamin B12, selenium, and other nutrients that support overall health. Eating fish regularly can be part of a balanced diet, and replacing some higher-fat processed meats with seafood may be beneficial.

However, not all fish are alike.

Some large predatory species accumulate more mercury over their lifetimes. Some seafood products come from fisheries facing significant environmental pressures. Others may be mislabeled or substituted with a different species. Even an excellent fish can become an unpleasant meal if it has been stored improperly or overcooked.

The good news is that these concerns don't mean you need to avoid seafood altogether. In most cases, a little knowledge can help you make a better choice.

Here are 10 types of fish that may deserve a second thought when you see them on a restaurant menu—and what to consider before deciding whether to order them.

1. Swordfish: Delicious, but potentially high in mercury

Swordfish is a popular restaurant choice because of its firm texture and rich, meaty flavor. Unlike delicate white fish that can flake apart easily, swordfish holds its shape on a grill and can be served as a thick steak. Its substantial texture makes it particularly appealing to people who don't usually enjoy traditional flaky fish.

But swordfish has one important drawback: it is a high-mercury fish.

Mercury enters aquatic ecosystems through natural processes and human activities. Certain forms, particularly methylmercury, accumulate in fish tissue. Large predatory fish tend to have higher concentrations because they eat smaller fish and retain mercury over time.

Swordfish can live for many years and feed on other marine animals, giving mercury time to accumulate in its body. Regularly eating high-mercury fish can be especially concerning for pregnant people, those who may become pregnant, breastfeeding mothers, and young children because developing nervous systems are particularly vulnerable to mercury exposure.

This doesn't mean swordfish is automatically unsafe for every adult after a single meal. The concern is primarily about exposure over time and the amount consumed.

If you love grilled swordfish, consider how often you order it. For a lower-mercury alternative, ask about salmon, trout, sardines, or another species known to contain less mercury. Preparation matters, too, but grilling, baking, or frying does not remove mercury from the fish.

Restaurant tip: If you're choosing seafood for a child or during pregnancy, consult current local dietary guidance and favor lower-mercury options.

2. King mackerel: Don't confuse every mackerel species

Mackerel is often praised for its rich flavor and beneficial omega-3 fatty acids. It can be grilled, smoked, roasted, or served in a variety of traditional dishes. However, the name covers several species, and their nutritional and safety profiles are not identical.

King mackerel is one species that deserves particular attention because it can contain high levels of mercury.

The distinction is important because not every fish sold as mackerel carries the same mercury concern. Atlantic mackerel, for example, is generally considered a lower-mercury choice, while king mackerel appears on major public health advisories as a fish to avoid for people who are pregnant, breastfeeding, or feeding young children.

At a restaurant, the menu might simply say “mackerel,” especially in a dish where the fish is smoked, seasoned, or incorporated into a sauce. If the species isn't identified, asking a question can help you understand what you're ordering.

Mackerel also has a naturally oily texture, which can be wonderful when the fish is fresh. Its flavor may be stronger than that of mild white fish, so it is worth asking how the kitchen prepares it if you're unfamiliar with the species.

Restaurant tip: Ask which species is being served. If the answer is king mackerel, consider a different option, particularly if you need to limit mercury exposure.

3. Shark: A species group with significant mercury concerns

Shark meat appears in some coastal cuisines and may be sold under regional names or prepared as steaks, grilled portions, or traditional dishes. Its firm texture can make it appealing to diners who prefer a meatier seafood option.

However, shark is generally considered a high-mercury choice.

As long-lived predators, many shark species accumulate mercury through their diets. The amount varies by species, size, location, and other factors, but shark is included on prominent public health lists of fish that pregnant people and young children should avoid.

There are also environmental considerations. Some shark populations face pressure from fishing, and the sustainability of a particular product depends on the species, location, and fishing practices involved. It is not accurate to assume that every shark fishery has the same status, but neither is it wise to treat shark as an environmentally neutral choice.

Because different shark species can look similar once cut into steaks or fillets, diners may have limited ability to identify the exact species from appearance alone.

If shark appears on a menu, consider asking where it was caught, which species it is, and whether the restaurant can provide information about its sourcing. If you want seafood with less mercury, there are plenty of alternatives.

Restaurant tip: Given the mercury concerns and the variability in sustainability, shark is generally a fish worth skipping when lower-mercury options are available.

4. Tilefish: The species and fishing location matter

Tilefish may not be as familiar as salmon or cod, but it appears on some restaurant menus, particularly in establishments specializing in regional seafood or premium fish dishes.

It has a delicate, sweet flavor and a texture that works well with simple preparations such as roasting, pan-searing, or serving with butter-based sauces. Its mild taste can make it an appealing choice for diners who prefer fish without an especially strong ocean flavor.

The concern is mercury. Some tilefish populations have been found to contain high concentrations, and public health advice specifically identifies Gulf of Mexico tilefish as a high-mercury fish.

The distinction between populations matters. Fish with the same common name can have different mercury levels depending on their habitat and other biological factors. A broad label such as “tilefish” may not tell a diner enough to assess the exact source.

This is particularly relevant for pregnant people, those who may become pregnant, breastfeeding mothers, and children. For these groups, current government guidance generally recommends avoiding Gulf of Mexico tilefish and selecting safer alternatives.

Tilefish also illustrates why a restaurant's sourcing information can be valuable. A menu that identifies the species and catch location gives diners a clearer picture than one that offers only a generic name.

Restaurant tip: If the menu lists tilefish, ask about the species and origin. When that information isn't available, choosing a well-established lower-mercury alternative is the simpler option.

5. Bigeye tuna: A popular favorite with a catch

Tuna is a restaurant staple. It appears in sushi, poke bowls, salads, sandwiches, and grilled steaks. Its versatility and distinctive flavor have made it one of the most recognizable seafood choices around.

But “tuna” is not one single species, and the differences can be significant.

Bigeye tuna is a large, predatory species that can contain relatively high mercury levels. It is frequently associated with sushi and sashimi, where its rich flavor and firm texture are prized.

For people who eat tuna frequently, the type of tuna matters. Canned light tuna is generally lower in mercury than albacore, while bigeye tuna is a higher-mercury choice. These distinctions can be hard to recognize when a restaurant menu uses a broad term such as “tuna” without specifying the species.

There are also sustainability questions. Tuna fisheries vary in their effects on fish populations and other marine animals, and responsible sourcing depends on the species, fishing method, and location. A restaurant that can identify its supplier or explain its sourcing practices offers diners more useful information than one that cannot.

It's worth remembering that raw preparation introduces separate food-safety considerations. Sushi-grade presentation does not eliminate every risk associated with raw seafood, and diners who are pregnant or immunocompromised should follow appropriate medical and public health advice.

Restaurant tip: Ask which tuna species is served, particularly if you eat tuna often. Salmon, trout, and other lower-mercury fish can be good alternatives when you want to vary your seafood choices.

6. Orange roughy: A slow-growing fish with sustainability concerns

Orange roughy has a mild flavor and delicate white flesh, making it appealing to people who want a simple, understated seafood meal. It can be served baked, pan-seared, or incorporated into dishes with herbs, lemon, and butter.

Its main concern is not simply the way it tastes or how it is prepared. Orange roughy is known for its exceptionally slow growth and long lifespan.

These biological characteristics make the species vulnerable to fishing pressure. Orange roughy can take many years to mature and may live for well over a century. When a slow-growing fish population is depleted, rebuilding it can be difficult because the fish reproduce relatively late in life.

Deep-sea fishing can also raise environmental concerns, depending on the method used and the habitat affected. Bottom-trawling operations, for example, can damage vulnerable seafloor ecosystems.

That doesn't mean every orange roughy fishery has the same environmental status. Management practices, fishing location, and current population assessments all matter. Nevertheless, the species has long been highlighted in seafood sustainability discussions because of its biological vulnerability.

For diners who want to make environmentally conscious choices, it is worth checking a current seafood guide or asking the restaurant where the fish came from.

Restaurant tip: If the restaurant cannot provide reliable sourcing information, consider a more readily traceable alternative, such as responsibly sourced farmed trout or a well-managed fishery's product.

7. Chilean sea bass: Premium taste, complicated sourcing

Chilean sea bass is prized for its rich, buttery flavor and large, moist flakes. Despite its name, it is not a true sea bass; the commercial name generally refers to Patagonian toothfish, a species found in cold Southern Ocean waters.

Its texture makes it popular in upscale restaurants, where it is often served with refined sauces, vegetables, or carefully prepared side dishes. For many diners, it is a luxurious alternative to more familiar white fish.

However, its history includes significant sustainability challenges. Demand for the fish increased dramatically as restaurants embraced it, creating incentives for illegal and unregulated fishing in some areas. Management and traceability have improved in certain fisheries, but sustainability still depends on where and how the fish was caught.

The name alone does not reveal whether a portion comes from a well-managed fishery or a less responsible source. Certification, traceability, and the specific fishery can all make a difference.

Chilean sea bass is not inherently a poor choice in every circumstance. A responsibly sourced portion may be a more defensible option than one with no clear origin. The key is to avoid assuming that an expensive menu price guarantees ethical sourcing.

Restaurant tip: Ask whether the fish is traceable to a well-managed fishery and whether the restaurant follows a recognized seafood sustainability standard. If staff cannot answer, another species may be easier to evaluate.

8. Farmed salmon: A question of how it was raised

Salmon is one of the most popular fish in restaurants, and it offers several nutritional benefits, including protein and omega-3 fatty acids. Its flavor and versatility make it suitable for everything from grilled fillets to sushi and pasta dishes.

Farmed salmon deserves a closer look, but not because all farmed salmon is unhealthy or unsafe. Aquaculture varies considerably, and many responsible farms produce nutritious fish under carefully managed conditions.

The concerns are more nuanced. Depending on the farm and production system, issues can include waste discharge, the use of medicines to manage disease, parasites, interactions with wild salmon, and the sourcing of feed. Environmental performance varies by region, farming method, and regulatory oversight.

The nutritional profile can also differ between wild and farmed salmon, partly because of diet. Farmed salmon often contains more fat overall, while both farmed and wild salmon can provide beneficial omega-3 fats. Neither category is automatically superior in every nutritional respect.

Another common misconception is that the color of salmon tells you whether it is natural or safe. Farmed salmon's pink or orange color can come from pigments added to its feed, reflecting compounds also found in the diet of wild salmon. Color alone is not a reliable indicator of quality or safety.

Restaurant tip: Rather than avoiding farmed salmon entirely, ask about the producer or country of origin when that information is available. A reputable supplier and transparent sourcing practices are more useful than assuming all farmed fish are the same.

9. Imported basa or swai: Understand what you're being served

Basa and swai are names commonly used for farmed fish in the catfish family, particularly products imported from Southeast Asia. Their mild flavor, soft texture, and relatively low price make them popular in casual restaurants, cafeterias, and prepared seafood dishes.

They are not inherently dangerous fish. Properly farmed and handled basa or swai can be a reasonable source of protein. The concern is that diners may not always know the species, farming conditions, or supply chain behind a menu item described simply as “white fish.”

As with any farmed seafood, quality depends on production standards, water conditions, feed, veterinary oversight, processing, and transport. Regulatory systems and inspection practices differ between countries, but it would be misleading to assume that every imported product is unsafe or that every domestic product is superior.

Mislabeling is another reason to pay attention. Seafood substitution can occur at various points in the supply chain, and inexpensive fillets may be used in dishes where sauces, breading, or seasoning make species difficult to identify. That doesn't establish that a particular restaurant is doing anything wrong; it simply explains why clear labeling and traceable sourcing matter.

The texture of basa and swai is also softer than that of some firmer white fish, which may affect the eating experience. A diner expecting a thick, flaky cod fillet may find the result different from what they imagined.

Restaurant tip: Ask which species is being served and whether the restaurant can identify its supplier. If you prefer a firmer texture or more traceable sourcing, cod, haddock, or responsibly sourced pollock may be alternatives, depending on availability.

10. Escolar: The fish that can cause digestive trouble

Escolar is sometimes served as a rich, buttery white fish, and it can be especially appealing to diners who enjoy a smooth texture and mild flavor. It has appeared in sushi restaurants and seafood establishments, sometimes under names that do not make its identity immediately clear.

Its main concern is unusual: escolar contains high levels of naturally occurring wax esters, which humans do not digest well.

Eating escolar can cause gastrointestinal symptoms, including diarrhea, abdominal cramping, and oily bowel movements. These effects are sometimes referred to as keriorrhea. The likelihood and severity can vary with the amount consumed and individual sensitivity.

Because the fish can resemble other white-fleshed species when served as a fillet or sushi portion, accurate labeling is important. Diners may not realize what they are eating if the menu uses a vague description or if the fish is substituted for another species.

The risk is not the same as mercury poisoning, and it does not mean escolar is contaminated or spoiled. It is related to the fish's natural composition. Cooking does not reliably remove the wax esters responsible for the problem.

Some jurisdictions have specific rules or guidance concerning escolar, and responsible restaurants should identify it accurately.

Restaurant tip: If you see escolar on the menu, understand that it can cause digestive discomfort even when fresh and properly prepared. If you have a sensitive digestive system or simply want to avoid that risk, choose a different fish.

How to make smarter choices when ordering seafood

Knowing which fish deserve extra attention is useful, but the larger lesson is that seafood decisions should be based on several factors rather than a simple list of “good” and “bad” species.

First, consider mercury. Large predatory fish such as swordfish, shark, king mackerel, and bigeye tuna are among the species that may require more caution. For people who are pregnant, breastfeeding, or feeding young children, following current public health guidance is especially important.

Second, think about sustainability. The environmental impact of seafood depends on the species, fishing location, fishing method, farming system, and management practices. A fish that raises concerns in one fishery may be a more responsible choice when sourced from another.

Third, ask about identification and origin. A restaurant that knows its supplier and can explain the species it serves is better positioned to answer questions about traceability. If the menu simply says “white fish,” asking what that means is perfectly reasonable.

Fourth, remember that freshness and food safety are separate from species choice. Fish should be handled and stored correctly, and raw seafood carries risks that cooking can reduce. An unpleasant smell, poor handling, or questionable storage is a reason for concern regardless of whether the species is normally considered a healthy choice.

Finally, don't let an alarming headline persuade you that seafood as a whole is something to fear. Fish can remain a nutritious part of a balanced diet. The goal is to vary the species you eat, pay attention to reliable advice, and choose reputable restaurants.

The bottom line

The next time you open a seafood menu, you don't need to interrogate the waiter about every detail or avoid every unfamiliar fish. A few practical questions can help you make an informed decision.

Swordfish and king mackerel raise mercury concerns. Tilefish requires attention to species and origin. Orange roughy and Chilean sea bass may call for closer scrutiny of sustainability and traceability. Farmed salmon and imported basa or swai should be evaluated on the quality of their sourcing rather than dismissed automatically. Escolar deserves special caution because it can cause digestive symptoms.

The most important point is that no single label tells the whole story. Price does not guarantee sustainability, a familiar name does not guarantee low mercury, and imported or farmed fish is not automatically inferior.

My restaurant-worker friend was right about one thing: ordering seafood becomes much easier when you look beyond the menu description. Learn a little about the fish, ask questions when necessary, and choose a variety of species from reliable sources.

You can still enjoy a beautifully prepared seafood dinner. You'll simply have a better idea of what's on your plate—and why you've chosen it.