Found in seafood, mostly in the form of worms. They are most common in tuna, salmon, cod, and swordfish. They are easily removed with a knife. To reveal the parasites a process called candling is used. This is where the fillet is put on a cutting board with a bright light shining up from underneath exposing any parasites. Freezing and cooking kills the parasites, however, it is more desirable to have them removed rather than cooking and eating them. Caution should be used in any fish that is consumed raw.