Customers calling Barney Greengrass’s appetizing emporium on the Upper West Side may find themselves on the phone with Moe, the 2-year-old son of owner Gary Greengrass. “Barney” and “Greengrass” are two of the first words Moe learned, according to his father.

Celebrating its 100-year anniversary today, the self-proclaimed “Sturgeon King,” which specializes in smoked fish, has become a New York institution and remains family-owned. That doesn’t mean Mr. Greengrass, 48, isn’t concerned about what his only son might choose to do in the future.

“He might disappoint me and become a doctor or a lawyer,” Mr. Greengrass said with a smile yesterday.

To celebrate its centennial today, the restaurant is turning back the clock to 1908 prices. That means customers can enjoy modern-day novelties like a 15-cent coffee (normally $2.25), eggs with a side of Nova Scotia salmon costing $1.40 (normally $10), or a $1.75 sturgeon (normally $17.50).

Under the ownership of its namesake, Barney Greengrass originally opened in 1908 at the corner of West 113th Street and St. Nicholas Avenue in Harlem. It moved to its current location in 1929.

Mr. Greengrass has tried to maintain the restaurant’s authenticity with relics of the past, such as wallpaper that has been hanging for 50 years and a refrigerator that’s so old his father used to call it an icebox. But the business has expanded in ways its founder could have never imagined.

Nowadays, Barney Greengrass has a burgeoning mail-order service that ships its signature smoked fish around the world, as well as a catering service for all sorts of events. There’s another restaurant bearing the same name in Beverly Hills. The New York restaurant, which includes a sit-down area and a takeout counter, served President Franklin Roosevelt, George Burns, Jerry Seinfeld, and tens of thousands of ordinary Upper West Siders over the years.

Family-owned Jewish-style restaurants are facing challenges. The Second Avenue Deli in the East Village was forced to close because of rising rents and later reopened further uptown and closer to Third Avenue.

Barney Greengrass, though, has stuck to its gills.

“On one hand, we want to change with the times, but on the other hand we’re like an old, comfortable shoe,” Mr. Greengrass said. “I don’t know any other places that focus in on the smoked fish.”

Some customers said they came not just for the fish but to support a family-operated business of a sort that used to be more abundant in the city.

“I think a lot of us come here because we’re afraid it’s going to disappear,” said a 52-year-old grant strategist, Robert Sawyer, who said he’s been a patron for 30 years.

That’s a fear he’ll have to take up with the youngest Greengrass, next time he calls.