Ontario gourmands are smacking their lips in protest over a new provincial regulation banning the use of fresh fish in raw dishes.

Affecting such menu items as tartare, ceviche, cold smoked fish and the popular Japanese delicacy sushi, the province has enacted a new regulation that forces chefs to use fish that's been previously frozen.

Ontario Ministry of Health officials are concerned that, otherwise, unwitting patrons could be served with a portion of a parasitic roundworm sometimes found in wild ocean fish.

Under the new law, a first in Canada, fish destined to be served raw must be frozen to minus 20 degrees for seven days or minus 35 degrees for 15 hours.

In restaurants around Ontario, however, some sushi masters are finding the new rules unpalatable. Freezing the key ingredient changes both texture and taste, they say.

Ottawa sushi chef Hiro Iida told CTV News he has been making sushi for fifteen years -- following centuries-old techniques.

"Chef knowledge, most important thing," Iida said, confident in his own skills, as well as Japanese tradition. His island homeland has, after all, been eating fresh sushi without incident for centuries.

On that basis, some call the new law an overreaction.

Dr. Jay Keystone, for instance, says that in his practice at Toronto general Hospital, he's never seen a case.

"I've been doing tropical medicine, parasite disease for 28 years, and in all that time I have not heard of a case, nor have I seen a case."

Others point out that some of the most popular fish served in sushi restaurants is already frozen.

Tuna, for example, is typically flash-frozen aboard the deep-sea trawlers where it can spend days before coming ashore.

Still, some sushi lovers say they've never been concerned about eating the Japanese delicacy.

When asked whether she's worried about eating raw fish, Ottawa restaurant-goer Kristen Smith laughed.

"No," she said, jokingly dismissing concerns of food-borne parasites. "Wasabi kills it, it's strong. And we need to build up our tolerance, too."

Even though they've yet to record a case of disease related to sushi, health officials say it's better to be safe than sorry.

"We in Ontario haven't had any reports of diseases per se," Ontario's associate chief medical officer of health, Karim Kurji, told The Globe and Mail. "But our concern is to do this on a precautionary basis rather than react to a disease when it shows up."

The ban on fresh fish went into effect on September 1.