Is it normal to find worms in fish?

Chef's answer
Parasites are a natural occurrence, not contamination. They are as common in fish as insects are in fruits and vegetables. Parasites do not present a health concern in thoroughly cooked fish. Parasites become a concern when consumers eat raw or lightly preserved fish such as sashimi, sushi, ceviche, and gravlax.
Frequently asked Questions 🎓
Commercially frozen seafood is frozen solid at a temperature of -35 degrees and stored at this temperature or below for a minimum of 15 hours to kill parasites.24 Feb 2017
Parasites are endemic in aquatic environments and infection of fish is unavoidable. In the seafood industry, freezing has been used to kill parasites.
Raw or undercooked freshwater crab or crayfish can contain Paragonimus. For instance, dishes that marinate crab and crayfish with with vinegar, wine, or brine to "chemically cook" them do not always kill the the parasite
Different pathogens may be present in crabs living in various environments. For instance, Paragonimus westermani , a parasite also known as lung fluke, may be present in freshwater crabs.
Drinking alcohol might actually kill pathogens in the human gut or bloodstream, much the way alcohol in the bloodstream of fruit flies kills their parasites.17 Feb 2012
Look to see if your fish has cloudy eyes, white patches or is gasping for air, rubbing on objects and is listless. Fish lice could cause these symptoms. Internal parasites will cause loss of appetite, listlessness and erratic swimming. Note redness, irritation and/or threadlike worms coming from the fish's tail area.
In general, killing parasites requires freezing and storing fish at a surrounding temperature of minus 4 degrees Fahrenheit or colder for seven days
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