What poisonous fish is served at restaurants?

The term "poisonous" is often used incorrectly when referring to fish. It's important to distinguish between poisonous and toxic fish:

* Poisonous fish contain toxins in their flesh that are harmful to humans, even when cooked properly. These are very rare and not typically served in restaurants.

* Toxic fish may accumulate toxins in their flesh from their environment, primarily from eating algae or other contaminated organisms. The level of toxins can vary depending on the fish, location, and season. These fish are sometimes served, but require careful handling and preparation to avoid consuming harmful levels of toxins.

Here are some examples of what people might mistakenly call "poisonous" fish, but are actually toxic:

* Pufferfish (Fugu): This fish contains tetrodotoxin, a deadly neurotoxin. It's only served by highly trained chefs in Japan, and even then, there is a risk of poisoning.

* Certain types of shellfish: Some shellfish, like mussels and clams, can accumulate toxins from algae blooms, leading to paralytic shellfish poisoning (PSP). These toxins are destroyed by heat, so properly cooked shellfish are safe to eat.

* Tuna: Certain types of tuna can contain high levels of mercury, especially large, older fish. Mercury is a heavy metal that can damage the nervous system, so it's important to consume tuna in moderation.

It's always best to err on the side of caution when it comes to fish. If you're unsure about the safety of a particular fish, ask your waiter or chef. You can also consult with a local fishmonger or the National Oceanic and Atmospheric Administration (NOAA) for information on safe seafood consumption.