Numerous types of fish can be caught all over the world, but not every fish is good to eat. Some fish have poisonous scales, slimy skin, or sharp teeth that can get lodged in your hand if you aren’t careful.
Even if you manage to catch a good fish, many others will be quicker to do so again because they are also more common in some locations. This is why we talk about the most dangerous types of fish you can catch in freshwater and saltwater.

Freshwater Fish
Freshwater fish are found in rivers, lakes, ponds, and other bodies of water that are less salty than the ocean. Most freshwater fish are great for eating. Some, like the paddlefish, even swim upstream to lay their eggs, invisible to humans. While freshwater fish are mostly safe to eat, some species are known to carry harmful diseases like hepatitis, purple mouth, and amoebic dysentery.
The FDA recommends that you avoid eating certain species of fish that are farmed in human-run facilities, like carp, salmon, and tilapia, due to the spread of infectious diseases. If you do decide to eat freshwater fish, make sure you thoroughly wash them before consuming them.
Nowadays, supermarkets and restaurants often keep their fish in enormous tanks, so you could go ahead and just ask them to wash the fish for you.
Saltwater Fish
Like freshwater fish, saltwater fish can be eaten, but more often they are caught as a sport or commercial fish and then eaten frozen or canned. Saltwater fish are found in oceans, seas, and other bodies of saltwater. Most saltwater fish are great to eat and safe to catch, but a few species are known to carry harmful parasites or are just too dangerous to eat.
One dangerous type of saltwater fish is the Bluefin Tuna, which has been overfished and is now endangered. Bluefin has a sweet, mild taste that has made it a delicacy around the world, but it has been overfished so much that it is now endangered. Bluefin is still eaten in some countries, but only by specially trained chefs.
The FDA also warns against eating sharks and other large carnivorous fish that are caught in dangerous ways, including by using hooks and lines that are too heavy, or that may have been used to catch other fish that may be poisonous.

Tuna and Other Large Gamefish
Most types of tuna such as yellowfin and bluefin can be safely eaten raw, but they are dangerous when people attempt to eat them in a way that is not recommended. Tuna and other large gamefish, such as marlin, swordfish, and king mackerel, are dangerous if they are not caught and prepared correctly.
These fish are dangerous to eat when they are not fresh, not properly handled, or if they have been caught and re-caught in the same body of water. It is wise to avoid eating these fish that are often caught by fishing boats.
Though these large and dangerous fish are often caught by large commercial fishing fleets, many individuals also fish for these same species. Neither group is licensed to do so, and both will be in danger if their illegal catches are eaten.
Catfish and Other Small Freshwater Fish
Catfish, other small freshwater fish, and all members of the carp family are safe to eat, but they should be thoroughly cooked before being eaten. Freshwater fish, the especially catfish, are often harvested as they spawn in rivers and lakes.
Since they are so common, you might assume they are safe to eat, but some of them, like blue catfish, have poisonous scales that could cause illness if they get lodged in your mouth.
The FDA also warns against eating certain species of catfish that are farmed in human-run facilities, like the channel catfish, due to the spread of infectious diseases. As a result, many catfish species are now farm-free.
Crayfish and Shrimp
Crayfish and shrimp are tasty additions to many dishes, but they can be dangerous to eat raw. Crayfish are freshwater scavengers that are harvested for food in parts of Canada, Europe, and parts of the United States. Shrimp are marine crustaceans that are found in saltwater.
Both types of seafood should be cooked thoroughly before being consumed. In some areas, crayfish farms have been known to spread disease, and some crayfish species can be dangerous.
Avoiding Dangerous Fish
The FDA recommends that you avoid eating certain species of fish that are farmed in human-run facilities, like carp, salmon, and tilapia, due to the spread of infectious diseases.
However, these same rules also apply to farm-free fish. Additionally, many types of fish are known to carry parasites that could be dangerous if they are eaten raw. In this case, the FDA recommends cooking fish thoroughly before eating it.
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If you want to ensure your fish is safe to eat, you should try to find fish that are farm-free or caught by a licensed fisherman. If you don’t know what type of fish it is, you can usually check its identifying information on the packaging, or ask at the store where you bought it.
If you’re still not sure, you can always freeze the fish you caught and keep it for later. You can read more information on freezing fish.