Yellowstone Park fish have parasites. Truth be told, most fish in any waters have parasites. If this bothers you, please safely release the fish you catch. If you know this, please clean, and cook your fish thoroughly.
The trout in the Yellowstone River, and Lake, are no less or more impacted by parasites than fish anywhere else. There are certainly more polluted waters around the world that have more parasites. The geothermal waters of Yellowstone Park do not promote parasites.
Besides parasites, Yellowstone waters are full of natural pollution toxins that originate from the geothermal features. Lead, arsenic, mercury, and other natural, harmful chemicals are stored in the fish’s fins, skin, and belly fat. Any river that comes out of Yellowstone Park, pollutes the fish. That is why most of these waters have Fish Consumption warnings.
The most common park parasite is the Adult round worm or Bulhodacnitis scotti. These are usually discarded with the guts. Most are found as cysts in the intestine and sometimes in the flesh.
Crepidostomum transmarinum is an adult fluke worm. These worms are found internally and are about a half inch long.
External parasites are also found on the Parks fish. Piscicola salmositica is a small leech about an inch long when extended. They are found on the fish’s skin.
Salmincola sp, is a fish louse, or small crustacean, that can be seen on the skins surface.
Other national waters contain Tapeworms. The parasite known as Diphyllobothrium latum are found more commonly in the Pike family of fishes. It is not found in the Yellowstone trout.
Park parasites are more aesthetic than of a real health concern. Most fishermen do not see them. Proper cooking kills the parasites, and they are consumed with no risks. Any fish sushi or raw recipe risks consuming parasites. Thoroughly rinse and clean any fish that you plan to eat raw. A slight salt bath will help eliminate any risks but will also flavor the fish.
Consume your catch carefully!