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

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

He said that when he eats out, he doesn't choose fish simply because the name sounds familiar or because it happens to be one of the most expensive options on the menu.

Instead, he thinks about where the fish came from, how it was handled, how it was prepared, how frequently the species is mislabeled, and whether there are environmental or health concerns associated with it.

That advice stuck with me.

Seafood has a reputation for being one of the healthiest foods you can order. Fish can provide high-quality protein and important nutrients, including omega-3 fatty acids, vitamin D, vitamin B12, selenium, and other minerals.

But not every fish on a restaurant menu is necessarily an equally good choice.

Some species can contain relatively high levels of mercury. Others can be associated with sustainability concerns. Certain fish are commonly substituted or mislabeled. Some depend heavily on how they were raised or caught, while others may become less appealing because of the way they are stored or prepared.

That doesn't mean you should be afraid of seafood.

It means you should know what you're ordering.

Here are 10 types of fish that may deserve a second thought when you encounter them on a restaurant menu.

1. Swordfish

Swordfish is a favorite in many restaurants because it has a firm texture and a rich, meaty flavor.

Unlike delicate white fish that can fall apart easily, swordfish holds its shape beautifully on a grill. It can be served as a thick steak, making it especially appealing to people who want something substantial.

But there is one major consideration: mercury.

Swordfish is a large predatory fish. Because these fish live for years and eat smaller fish, mercury can accumulate in their bodies over time.

The U.S. Food and Drug Administration lists swordfish among the fish that are highest in mercury and advises certain groups—including pregnant or breastfeeding women and young children—to avoid it. (FDA)

For healthy adults, an occasional serving is different from eating it regularly.

The lesson isn't that swordfish is automatically dangerous.

It's that frequency matters.

If you love swordfish, it may be worth treating it as an occasional choice rather than your standard weekly seafood order.

2. Shark

Shark can sometimes appear on menus under names that make it sound more approachable, depending on the region and restaurant.

But shark presents two separate considerations: mercury and sustainability.

Like swordfish, sharks are large predatory fish that can accumulate mercury.

The FDA places shark among the fish that consumers should avoid because of high mercury levels. (FDA)

There is also a broader environmental question.

Sharks play important roles in marine ecosystems, and many shark populations have experienced serious pressure from fishing.

That doesn't mean every shark fishery is identical.

Sourcing matters.

A restaurant that can explain where its seafood comes from and how it was harvested gives you more information than a menu that simply lists “shark” without any details.

3. King Mackerel

Mackerel is often considered a healthy fish, and that's part of what makes this one surprising.

Many types of mackerel are excellent seafood choices and can be rich in omega-3 fatty acids.

But “mackerel” isn't one single species.

King mackerel is a large predatory fish and is high in mercury. The FDA specifically recommends avoiding king mackerel. (FDA)

Other mackerel species can have very different mercury profiles.

So if a menu simply says “mackerel,” it can be worth asking what species is being served.

That small question can make a surprisingly large difference.

4. Tilefish

Tilefish is another example of why knowing the species matters.

Certain tilefish caught in the Gulf of Mexico can contain very high levels of mercury.

The FDA specifically lists tilefish from the Gulf of Mexico among the fish to avoid because of mercury concerns. (FDA)

However, there is an important distinction.

Not all tilefish comes from the same area.

Tilefish from the Atlantic is treated differently in federal consumer guidance.

This is why blanket statements such as “never eat tilefish” can be misleading.

If you see tilefish on a menu, asking where it was caught can provide useful information.

5. Bigeye Tuna

Tuna is one of the most popular seafood choices in the world.

It's found in sushi restaurants, seafood grills, sandwiches, salads, and countless other dishes.

But tuna varies enormously by species.

Bigeye tuna is a large species that can accumulate significant levels of mercury. The FDA includes bigeye tuna among fish that should be avoided. (FDA)

This can be particularly relevant for people who eat sushi frequently.

A single meal isn't necessarily the issue.

The concern is repeated exposure over time.

If tuna is one of your favorite foods, learning the difference between tuna species can help you make more informed choices.

For example, canned light tuna generally has much lower mercury levels than bigeye tuna, while albacore tuna falls somewhere higher.

The word “tuna” alone doesn't tell you everything you need to know.

6. Orange Roughy

Orange roughy became popular because of its mild flavor and delicate texture.

But there are reasons consumers may want to think twice before making it a regular choice.

First, orange roughy is a long-lived fish.

Some individuals can live for many decades, and long-lived predatory species can accumulate mercury.

The FDA places orange roughy among fish that consumers should avoid because of mercury levels. (FDA)

There are also sustainability considerations.

Because orange roughy can live for such a long time and reproduce relatively slowly, populations may be vulnerable to heavy fishing pressure.

A fish that takes many years to mature can be more difficult for fisheries to replenish.

That's an important reminder that seafood choices aren't only about nutrition.

They can also affect the ocean ecosystems from which our food comes.

7. Marlin

Marlin is another large predatory fish that can be high in mercury.

It sometimes appears in upscale seafood restaurants and can be served grilled, smoked, or prepared in other ways.

Its firm texture makes it attractive to diners who prefer meatier fish.

But the same biological characteristics that make large predatory fish impressive animals can also contribute to mercury accumulation.

The FDA includes marlin among the fish consumers should avoid because of mercury concerns. (FDA)

For someone who eats seafood occasionally, the key issue is knowing what you're ordering and how frequently you consume high-mercury species.

For children and people who are pregnant or breastfeeding, the guidance is more restrictive.

8. Escolar

Escolar is perhaps the most unusual fish on this list.

It has a rich, buttery texture that some diners absolutely love.

That richness, however, comes with a catch.

Escolar contains naturally occurring wax esters that humans cannot digest efficiently.

Eating too much can cause gastrointestinal symptoms, including oily diarrhea and stomach discomfort.

Because of this, some countries have specific rules concerning the sale or labeling of escolar.

One problem is that consumers may not always realize what they are ordering.

Escolar can sometimes be sold under names that are confusing to diners, depending on the market.

This is why transparency matters.

If a restaurant is serving escolar, accurate labeling and preparation information are important.

It isn't necessarily a fish that everyone must avoid.

But it is certainly one where portion size matters.

9. Imported Farmed Fish With Unclear Sourcing

This category is different from the others.

The problem isn't necessarily the species itself.

It's the lack of information.

Farmed seafood can be an excellent option. Aquaculture supplies a substantial share of the world's seafood, and well-managed farms can provide reliable sources of fish while reducing pressure on some wild populations.

But farming practices vary.

Water quality, feed, stocking density, environmental management, antibiotic use, and regulatory standards can differ depending on the country and production system.

That doesn't mean imported farmed fish is automatically bad.

It means consumers should avoid simplistic assumptions.

If a restaurant menu gives no information about the origin of a particular fish, asking the server where it was sourced can be useful.

Restaurants that take seafood seriously are often able to provide that information.

10. Fish With an Unclear Name or Suspiciously Generic Description

This may be the most practical warning of all.

Sometimes the issue isn't the fish you recognize.

It's the fish you don't.

Menus may use broad terms such as “white fish,” “local catch,” “market fish,” or other descriptions that tell diners very little about the species.

In some circumstances, seafood mislabeling can result in one species being substituted for another.

Research and regulatory testing have repeatedly found seafood mislabeling in different markets.

That matters because different species can have different prices, sustainability profiles, allergen considerations, and mercury levels.

If you are paying a premium for a particular fish, it is reasonable to want to know what you are actually eating.

A reputable restaurant should not be offended by a straightforward question.

The Mercury Question Most People Overlook

Mercury is one of the biggest reasons some fish appear on lists like this.

But the subject can easily become confusing.

Mercury occurs naturally in the environment, and human activity has increased the amount entering some ecosystems.

In water, certain forms of mercury can be transformed into methylmercury, which accumulates in fish.

Large predatory fish tend to have higher concentrations because they consume many smaller fish over their lifetimes.

That is why fish such as swordfish, shark, king mackerel, marlin, and bigeye tuna can be higher in mercury.

The solution isn't to stop eating fish.

In fact, the FDA and EPA emphasize that eating fish can provide important nutritional benefits.

Instead, consumers are encouraged to choose a variety of lower-mercury fish.

Fish Can Still Be One of the Best Things on the Menu

After reading a list like this, it would be easy to conclude that ordering seafood at a restaurant is risky.

That's not the message.

Fish can be an excellent part of a balanced diet.

The goal is variety.

Instead of eating the same high-mercury species repeatedly, consumers can choose options that are generally lower in mercury.

Examples include salmon, sardines, trout, shrimp, pollock, and other fish and seafood that fall into lower-mercury categories.

The FDA's consumer guidance provides a useful framework for making these choices. (FDA)

Ask Your Server One Simple Question

One of the best habits you can develop is surprisingly simple.

Ask:

“Where is this fish from?”

That question can tell you a lot.

You may learn whether the fish is wild-caught or farmed.

You may learn the country or region where it was harvested.

You may even discover that the restaurant has a detailed sourcing policy.

You can also ask:

“What species is it?”

That is particularly useful when the menu uses a generic description.

And if you're concerned about mercury, ask whether the fish is considered a lower-mercury choice.

A good restaurant should be able to answer basic questions about its menu.

The Freshness Factor

Sourcing isn't the only consideration.

Freshness and handling matter enormously with seafood.

Fish is highly perishable, and temperature control is critical from the time it is harvested until it reaches your plate.

A restaurant with strong food-safety practices should have systems for receiving, storing, and preparing seafood safely.

As a customer, pay attention to obvious warning signs.

Strong unpleasant odors, poor food handling, visibly deteriorated seafood, or a restaurant that appears generally unhygienic should make you reconsider your meal.

Fresh fish shouldn't smell overwhelmingly “fishy.”

A clean, mild marine smell is generally more reassuring.

The Preparation Can Change the Meal Completely

Even a nutritious fish can become a less healthy choice depending on how it is prepared.

A grilled salmon fillet and a heavily breaded, deep-fried salmon dish are nutritionally very different meals.

Cream-based sauces, large amounts of butter, heavy breading, and deep frying can add substantial calories, saturated fat, and sodium.

That doesn't mean you can never order fried fish.

Food is also about enjoyment.

But if your goal is a healthier meal, preparation matters.

Ask whether the fish can be grilled, baked, steamed, or broiled.

Sometimes that one change can make your restaurant order significantly lighter without sacrificing flavor.

The Real Lesson Behind the “Never Order” List

The title “10 fish you should never order at a restaurant” is certainly attention-grabbing.

But the reality is more nuanced.

There are very few foods that need to be placed into a simplistic category of “never eat” for every person.

Health, age, pregnancy, portion size, frequency, species, sourcing, and preparation all matter.

For some people, avoiding high-mercury fish completely is appropriate.

For others, an occasional serving may fit within dietary guidance.

The important thing is understanding the difference.

A Smarter Way to Order Seafood

The next time you sit down at a seafood restaurant, don't automatically choose the most expensive fish.

Instead, take a moment to think.

What species is it?

Where was it caught or raised?

Is it known to be high in mercury?

Is it a sustainable choice?

Is the restaurant transparent about sourcing?

How will it be prepared?

How often do you eat this type of fish?

Those questions can transform you from a passive customer into an informed seafood consumer.

And you don't need to become an expert marine biologist to do it.

The Bottom Line

My friend's advice at the fish restaurant initially sounded dramatic: there are supposedly 10 fish you should never order.

But the deeper lesson is much more useful.

Some fish deserve extra caution because they can contain high levels of mercury. Others raise sustainability concerns. Some may be associated with unusual digestive effects. And unclear labeling can make it difficult to know exactly what you're buying.

That doesn't mean seafood should disappear from your plate.

Quite the opposite.

Fish remains an important source of protein and nutrients, and choosing a variety of lower-mercury seafood can be a smart part of a balanced diet.

The next time you open a restaurant menu, don't be intimidated by the choices.

Be curious.

Ask questions.

Know your fish.

And remember that the best seafood decision isn't necessarily the most expensive item on the menu.

Sometimes, it's simply the on