We all know there’s plenty of fish in the sea, but sometimes keeping track of which of fish could be unsafe to eat can be difficult. If you love your seafood and want to stay healthy, safe and environmentally friendly, you might want to steer clear of the fish on this list.

1. Orange Roughy

In addition to its high levels of mercury, orange roughy can be a little, well, rough around the edges. Check out this quote from Seafood Watch: "Orange roughy lives 100 years of more, so the fillet in your freezer might be from a fish older than your grandmother." Holy moly. There’s fresh seafood and then there’s ancient seafood.

2. Swordfish

Fish that are top predators like swordfish spend their lives feeding on other fish. These other fish are often filled with mercury. Eat a fish that ate mercury and you’re eating mercury, too. Try sardines instead.

3. Shark

It was established long ago that people, orcas and polar bears at the top of the Arctic food chain were building up toxin levels in their bodies, sometimes dangerously so. These toxins were linked to accumulated pollution. More recently, scientists discovered that a population of Greenland sharks had accumulated more contamination that any of the other predators. In short, these sharks were more polluted than polar bears.

4. Imported Catfish

Most imported catfish that comes to the United States comes from Vietnam. Antibiotics that have been banned in the US are rampant in Vietnam. Even worse: the two varieties of Vietnamese catfish sold here, Swai and Basa, don’t technically count as catfish by the federal government and are inspected less strictly than other imported catfish.

5. American Eel

You may know this one by another name, like silver eel or yellow eel. A popular ingredient in sushi, this eel is particularly bad because it has high levels of PCBs and mercury. Beyond that, fisheries that these eel come from are contending with problems of pollution and overharvesting. If you don’t want to give this one up, try something safer with a similar taste like Atlantic or Pacific-caught squid.

Before you fear that you’ll never be able to enjoy a nice seafood meal again, be assured that there are plenty of good fish in the sea. It’s just a matter of reading up and making sure you’re making the healthiest choices possible to keep you and your family safe.