Does sushi-grade fish need to be frozen?

The U.S. Food and Drug Administration recommends that sushi-grade fish be stored for at least one week at a temperature of -4 degrees Fahrenheit, according to a PBS report. The reason for freezing fish is to destroy naturally occurring parasites in order to make the fish safe for raw consumption.

Sushi-grade fish should not be stored with non-sushi-grade fish or handled with the same knife, as this can cause cross-contamination. Good fish mongers should follow this freezing process prior to selling sushi to consumers because the freezing process is part of what makes it sushi grade. Unfortunately, however, there are no regulations in the United States that mandate special treatment of sushi-grade fish by fish mongers, the PBS report said.