How Sushi Parasites or Sushi Worms are Dealt With
Parasites or worms in raw fish are a sensitive issue when it comes to sushi. The truth is that it should not be too much of a concern, but it is better to be safe, and knowledgeable about this matter so that you can determine what the risk factors are for yourself and decide whether or not you want to consume raw fish.
The Japanese fishermen, and fish mongers have known about parasites in seafood for hundreds of years, and know which fish are safe from them. Not all fish are consumed raw in
Most parasites which are fully grown into worms are visible and obvious. Fishes that contain these do not even make it to the fish market. The parasites that are of concern, if any, are the tiny larvae and the young parasites that are present in bonito and salmon. The tentacularia is found in a low percentage of bonito, and the anisakis is found in a very few salmon since it lives in fresh water during mating season. The existence of these parasites were known for a long time. The bonito has a lesser chance of having parasites which have a characteristic of living right under the skin. For this reason, the skin, along with a few millimeters of flesh underneath was always charred before it was served (tataki method). As for salmon, it was never used for sashimi or sushi until very recently.
When consuming raw fish, it is very important to go to a restaurant or market which specializes in them. Sushi puts a lot of weight on freshness of the ingredients, and "fresh catches " sound really appetizing on the menu, but you should be careful which type of fish you are consuming. It isn't rude to ask if they were freeze treated or not. Freeze treated fish are considered lower in value and some serious sushi chefs may take the question in a different meaning, but nothing is more important than keeping your body away from parasites.