Stung by a shrinking economy, local food retailers are using technology to draw diners.

There are varying degrees to this trend. Some struggle to engage customers via Twitter and Facebook. Others, who are more tech savvy, create tools for the smaller screens of mobile devices. They compete against chain restaurants that can afford more innovative technologies, such as the iPhone apps that allow easy ordering at Pizza Hut and Chipotle Mexican Grill.

And as retailers master one technology, new ones arrive. One with a lot of buzz is Google Wave, an interactive whiteboard that lets multiple users edit text and add photos, videos and more -- all at the same time.

"Everything is progressing so fast," says Chris Shackelford, co-owner of Trelio restaurant in Old Town Clovis. "To know what's coming next, to know how to adapt, you have to be on top of it."

There's a sense of urgency among food retailers. To lure diners with thinner wallets, retailers must maximize their marketing dollars.

How bad is it? Consider this: Fresno had 750 registered restaurants, fast-food joints, refreshment stands and cafés as of June 30, down from 828 since the beginning of the year, says city business tax supervisor Connie Alfaro. In June of 2007, there were 886 such businesses.

It's a lot of work to learn and maintain Internet marketing tools, but many of the techniques are less expensive than print advertisements in newspapers and magazines, or radio and television spots.

For example, Roger Rocka's Dinner Theater reduced traditional advertising and started gathering Twitter followers and Facebook fans.

"We just try to do it as cheap as possible," says Dave Filipczak, who handles Roger Rocka's group sales and Twitter page.

The dinner theater also wants to grow its audience, which tends to be middle-age or older, he says. Roger Rocka's chose social networking tools "to get younger people interested."

Twitter and Facebook help push its shows and give updates about the remodeling of its building. The theatre focuses on residents of the Fresno metropolitan area; cast members help it build an online community.

But during the holiday season, Roger Rocka's still invests in a lot of traditional advertising to promote gift certificates to a wider audience. These are a "great gift for Mom and Dad and a lot of those people aren't on Twitter and Facebook," Filipczak says.

At Trelio, Shackelford has a more comprehensive approach to Internet marketing.

A version of Trelio's Web site for mobile devices will debut in a couple of weeks, which will allow customers to take reservations online.

He uses Twitter to give quick wine reviews, link to photos of dishes and recipes (such as the one for port wine ice cream at his blog, trelio.wordpress.com) and chat with different groups of friends.

"A conversation with a key person can open you up to lots of other key people," he says.

Shackelford saves most of the hard sell for his weekly e-mail newsletter, which accounts for 40% of Trelio's business.

"E-mail really needs to be at the center of every marketing campaign," he says. "People's time in front of a computer is much greater than their time in front of a magazine."

He's found Facebook ads to be effective. For Trelio's cooking classes, he targets folks who like chef Anthony Bourdain, Food Network, farmers markets and the like. To fill an expensive wine dinner, he'll set the ads to certain ZIP codes, as well as keywords such as "Coach" and "Louis Vuitton."

There's also a general ad for the restaurant that appears more than 11,000 times a day on Facebook, Shackelford says. The weekly cost for that ad: about $9.