A shortage of whitefish in the Great Lakes region is coming at an inconvenient time for Jewish families: the Passover holiday is when demand is high because it's a key ingredient in a traditional recipe.

The shortage has been partially caused by the winter deep freeze that blanketed the region for months.

Markets in Detroit, Chicago and Windsor, Ont., were among those struggling to fill whitefish orders before the beginning of the eight-day celebration Monday evening.

Mediterranean Seafood in Windsor, directly across the river from Detroit, received no orders of whitefish this week because of the shortage.

Owners at Mediterranean Seafood said they will lose $500 CAN this week as a result of the whitefish shortage.

Manager Ross Aiuto said he had to turn people away.

A representative of a commercial fishing agency said the shortfall extended as far as New York.

"Everybody's pulling their hair out," said Kevin Dean, co-owner of Superior Fish Co., a wholesaler near Detroit whose latest shipment provided just 75 pounds of whitefish although he requested 500 pounds. "I've never seen it this bad this time of year."

Gefilte fish a tradition

The dish that inspires such angst is gefilte fish, which somewhat resembles meat loaf or meatballs. Recipes handed down for generations vary but typically call for ground-up fish and other components such as onions, carrots, eggs and bread crumbs. Other fish such as cod, pike and trout are sometimes a part of the mix, but whitefish is especially popular.

"Just smelling that gefilte fish aroma tells my senses that it's a Jewish holiday," said Jason Miller, a rabbi and director of a kosher food certification agency in West Bloomfield, Mich.

In the Chicago suburb of Skokie, Ill., Ira Kirsche of Hungarian Kosher Foods said his market ordinarily would get 200 to 300 pounds of whitefish daily this time of year but has had to settle for 10 to 20 pounds.

Justin Hiller's family market in suburban Detroit eventually received the 4,000 pounds it needed to meet demand but it was a close call.

'We had to create a waiting list.'- Justin Hiller

"There was a short period a couple of days before Passover where we had to create a waiting list," he said.

Gefilte fish ("gefilte" is a Yiddish word for "stuffed") originated in eastern Europe, where it was an inexpensive and tasty choice for Sabbath and holiday meals, Miller said. Because it could be prepared ahead of time, it provided a way to avoid violating the Jewish law against deboning fish on the Sabbath.

It's also available frozen or in cans or jars. But for many, only homemade will do.

Elyse Fine of Rochester, N.Y., who travels to the Chicago area yearly to prepare Seder meals for extended family, said her family used jar varieties until about 10 years ago when her husband suggested she try producing it from scratch.

"Everybody loved it," Fine said. "Now they don't want me to go back to the jar stuff."

She finally located some whitefish an hour's drive away after coming up short at stores closer to home.

90% of Great Lakes surface froze

The whitefish shortfall is yet another ripple effect of the bitterly cold winter, which caused more than 90 percent of the Great Lakes surface area to freeze over. In some places, the ice cover was many feet thick, leaving commercial crews stuck in port.

"You have a lot of boats that can't get out to fish, even now," said Chuck Bronte, senior fishery biologist with the U.S. Fish and Wildlife Service in Green Bay, Wis.

Native American crews in northern Lake Michigan and Lake Huron, as well as Lake Superior, were able to drop their nets through holes drilled in the ice, said Mark Ebener, fishery assessment biologist with the Chippewa Ottawa Resource Authority, which regulates tribal fishing in the area.

They had some success but the whitefish population has dropped in recent years, making the Passover shortage worse, he said.

The reason is unclear, although some scientists blame invasive mussels, which create food scarcity in aquatic food chains by gobbling vast amounts of plankton.

With files from CBC