The Stratford Shakespeare Festival in southwestern Ontario has put more than 30 performances on hold because of slow advance ticket sales.

A preview show of West Side Story, slated for April 30, has been cancelled outright.

And another 30 other performances, mainly in the fall, have been put on hold. Almost every show in the well-regarded festival's repertoire has been affected.

Patrons who had shown interest in those programs or bought tickets have been asked to switch to a performance the day before or the following day, according to Stratford media manager Ann Swerdfager.

"Part of this is about audience and artist experience. It's not as enjoyable to sit in a half-full house as it is to sit in a full house," Swerdfager told CBC News.

She said box office revenues are down 15 per cent so far this season, with sales from the U.S. off significantly.

"Fifty per cent of our U.S. sales are from Michigan, and they have been hard hit there by the recession," she said. "It affects entertainment and tourism spending."

There has also been a downturn in sales from Canada, but Swerdfager says Canadian sales were down this time last year, and recovered by the fall.

If further shows are cancelled, it could save up to $1.5 million, she said.

Swerdfager said actors are paid by the week, whether they perform or not, but there are savings to be had in not having to change sets between performances or run the front of the theatre.

The performances will be reinstated if there is an upturn in ticket sales later in the year.

She admitted the holds were unprecedented, but said "it's not that big a deal."

"It hasn't been done before, but maybe because it has not been put forward as an option. We've certainly weathered recessions before," Swerdfager said.

Last year, the Shakespearean theatre festival posted a deficit of $2.6 million and reported a four per cent decline in attendance.

In early 2009, 11 people in administrative and production positions were laid off.

The Shaw Festival in Niagara-on-the-Lake, Ont., has also seen box office decline of about 15 per cent, but a spokeswoman said it has no immediate plans to put shows on hold.

Earlier this week, the National Ballet of Canada cancelled its fall tour of Western Canada because of reduced revenues.

With files from The Canadian Press