So, tuna is the exception to the rule of being required to be frozen to kill parasites.
"Food and Drug Administration regulations stipulate that fish to be eaten raw -- whether as sushi, sashimi, seviche, or tartare -- must be frozen first, to kill parasites. ''I would desperately hope that all the sushi we eat is frozen,'' said George Hoskin, a director of the agency's Office of Seafood. Tuna, a deep-sea fish with exceptionally clean flesh, is the only exception to the rule."